It's that time of year again: The evening now arrives earlier than many people punch out of work. On Sunday, Nov. 2, the clocks fell back by an hour for residents of 48 U.S. states and Navajo Nation, marking the end of daylight saving time (DST). In Europe, DST ended on Sunday, Oct. 26.

Despite the American Academy of Sleep Medicine (AASM) being in favor of establishing permanent standard time, many individuals want to keep DST year-round. In a Live Science poll published Oct. 28, we asked our readers what they thought about the contentious issue, asking whether or not they would get rid of daylight saving time.

In what is now the largest Live Science poll to date, 3,280 readers responded by the end of the voting window on Nov. 6. The vast majority said they would eliminate DST, with 76% stating they would stick to standard time, permanently. Meanwhile, 18% said they would rather remain in DST year-round.

Only about 4% of respondents wanted to keep the status quo, while approximately 1% said they would prefer to continue flicking between DST and standard time, but just not in the same way as we do under the current system. The remaining 1% hadn't made up their minds.

"I would be up for scrapping it. DST just seems so pointless," said Devin Smith, from Detroit. Fellow Michiganders shared this view, with Rob Beare echoing a preference for standard time because "10 pm daylight in the summer isn't as important as 8 am sunlight in winter when kids are trying to safely make their way to school."

But others explained they would stay in DST permanently because they wanted lighter evenings. "More evening daylight means more useful time after work/school," "M'Lud" wrote. "Waking up in the dark feels normal. Arriving home in the dark can be depressing."

Dave M agreed, stating a preference for year-round DST to get rid of "that yearly November shock of suddenly driving home from work in the dark." Dave added that the annual fall back also limits the opportunities for recreational activities, with Jane B also noting that permanent DST would "make it easier to accomplish post-business hour tasks."

Others were led by the research on the negative health repercussions of a mismatch between our body clocks and the environment. "The science is clear and standard time is solar time," PazKe said. "It shouldn't even be a question."

What do you think? Share your view in the comments below.

Many countries observe daylight saving time (DST), in which clocks get pushed ahead one hour in March to gain more hours of daylight in the spring and summer. In the U.S., all but two states, Hawaii and Arizona (except for Navajo Nation) observe DST and thus are preparing to make the switch back to standard time on Sunday Nov. 2.

Not everyone is happy with this routine change, however, with recent surveys showing that 54% of Americans and 42% of Britons want to scrap DST altogether.

The American Academy of Sleep Medicine (AASM) favors permanent standard time because it is better aligned with our circadian rhythm, the body's internal clock. Because light exposure regulates the circadian rhythm, a mismatch between our body clock and the environment can lead to problems such as reduced sleep, higher heart rate and blood pressure, and impaired immune function, AASM representatives wrote in a position statement.

Last month, we reported on a study predicting that abandoning DST and permanently staying on standard time could prevent over 2 million obesity cases and around 300,000 strokes a year in the U.S. by better aligning our circadian rhythm with the environment.

Yet others suggest there are benefits to keeping DST. Recent research, which has yet to be peer-reviewed, reviewed 157 studies from 36 countries on the links between DST and health outcomes and found evidence for fewer deaths and traffic accidents in the summer.

So, if it were up to you, would you abandon daylight saving time? Take our poll, and let us know what you think of each time policy in the comments below. If you choose "I'm undecided," what would persuade you either way?

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Abandoning the biannual switch to daylight saving time could prevent more than 300,000 strokes and slash over 2 million obesity cases a year, a new model using data from over 300 million Americans suggests.

Adopting permanent standard time (ST) takes less toll on our circadian rhythm — the body's rough 24-hour pacemaker — than daylight saving time (DST) or flicking between the time policies twice a year, the researchers found.

As a result of this reduced burden on our body clock, staying in ST year round could prevent almost 900,000 more cases of obesity and around 85,000 more strokes a year than remaining in DST year-round, the scientists concluded in a study published Sept. 15 in the journal PNAS.

"We can't propose public policy without data," study co-author Jamie Zeitzer, a professor of psychiatry and behavioral sciences at Stanford University, told Live Science. The data from this research marks "the beginning of a conversation," he said.

Time for a change?

DST, which makes clocks wind forward by an hour every spring, was first introduced in the U.S. in 1918 to save fuel during World War I. It was later made federal law by the Uniform Time Act of 1966.

Our circadian rhythm regulates and coordinates the functioning of each cell in the body. This internal pacemaker is highly sensitive to light exposure, and disruptions to it — for instance, when people must wake up or stay awake during dark hours — creates a "circadian burden" that has been associated with a measurable increase in negative health outcomes, including heart attacks, strokes and car accidents around the time of the switchover.

Insufficient sleep and a circadian burden are also metabolic stressors associated with reduced energy expenditure and excess food intake — risk factors for weight gain and obesity. As such, the position of the American Academy of Sleep Medicine is to scrap DST altogether and permanently stick to ST. Although the health risks of biannual switching are low for individuals, the effects are noticeable at the population level, Zeitzer said.

"You're really looking at lottery ticket kind of risk. But if 350 million people are doing it on the same day, someone's going to win the lottery," Zeitzer told Live Science. "[It's] just not one that you want to win."

To model the health impacts of a mismatch between circadian rhythm and the environment, Zeitzer and colleague Lara Weed, a bioengineer at Stanford University, calculated the circadian burden associated with each time policy: permanent ST, permanent DST and biannual shifting.

To do this, they simulated artificial light and sunlight exposure for the people in every U.S. county across a year under all three time policies. They assumed regular sleep routines (10 p.m. to 7 a.m.), and regular work schedules in a well-lit office (9 a.m. to 5 p.m., Monday to Friday).

The team found that biannually flicking between time policies created the largest disruptions to circadian clocks and therefore the largest circadian burden.

The researchers then used data on county-level prevalence of chronic diseases to determine how the different circadian burdens predicted eight health outcomes: arthritis, cancer, chronic obstructive pulmonary disease, coronary heart disease, depression, diabetes, obesity and stroke. They controlled for various socioeconomic and health factors that could also determine disease prevalence, such as high blood pressure, health insurance status and unemployment.

Sticking to ST would prevent around 2,602,866 cases of obesity and 306,988 strokes compared to a biannual shift. Permanent DST prevented obesity and strokes to a lesser degree, with 1,705,437 fewer predicted obesity cases and 220,092 fewer strokes on average, compared to the biannual switch.

Their model found neither policy led a statistically meaningful reduction in the six other health outcomes.

However, the research is based on simulations which deliberately included unrealistic assumptions, including universal regular light exposure and sleep, and it also did not consider seasonal variations in behavior. Moreover, the health outcomes dataset relied on self-reported information, such as for body mass index (BMI) and whether they'd had a past stroke or not.

Also, they did not include race in their model, despite there being persistent racial and ethnic disparities in sleep in the U.S. This exclusion "doesn't necessarily change the results of the study," said Karin Johnson, a professor of neurology at UMass Chan School of Medicine-Baystate and a spokesperson for the American Academy of Sleep Medicine, who was not involved in the research.

It does mean, however, that the increased risks of stroke and obesity are likely to be felt most keenly by people [namely, Black and Hispanic or Latino populations] that are "already at risk for sleep disparities from other causes," Johnson told Live Science in an email.

We fell back — now, it's time to spring forward again.

Daylight saving time will officially begin in North America on Sunday March 8, 2026, when clocks move forward by an hour. In most of Europe, meanwhile, daylight saving time, or British Summer Time as the U.K. calls it, begins on Sunday March 29, 2026.

Daylight saving time (sometimes erroneously called daylight SAVINGS time) ends again on Nov. 1, 2026 in the U.S., and on Oct. 25, 2026 in most of Europe and the U.K., when we will move our clocks back by an hour.

These spring and fall time changes continue a tradition started during World War I.

Here's a look at when daylight saving time starts and ends during the year, so you know when to change your clock and not miss an important engagement. You'll also learn about the history of daylight saving time, why we have it now and some myths and interesting facts about the time change.

When does the time change?

Historically, daylight saving time (DST) has begun in the summer months and ended right before winter, though the dates have changed over time as the U.S. government has passed new statutes, according to the U.S. Naval Observatory (USNO).

So when does the time change? Starting in 2007, DST begins in the U.S. on the second Sunday in March, when people move their clocks forward an hour at 2 a.m. local standard time (so at 2 a.m. on that day, the clocks will then read 3 a.m. local daylight time). Daylight saving time then ends on the first Sunday in November, when clocks are moved back an hour at 2 a.m. local daylight time (so they will then read 1 a.m. local standard time).

(In most of Europe, daylight saving time begins on the final Sunday in March, and ends on the final Sunday in October.)

Why did daylight saving time start?

Benjamin Franklin takes the honor (or the blame, depending on your view of the time changes) for coming up with the idea to reset clocks in the summer months as a way to conserve energy, according to David Prerau, author of "Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time" (Thunder's Mouth Press, 2005). By moving clocks forward, people could take advantage of the extra evening daylight rather than wasting energy on lighting. At the time, Franklin was ambassador to Paris, and he wrote a witty letter to the Journal of Paris in 1784, rejoicing over his "discovery" that the sun provides light as soon as it rises.

Even so, DST didn't officially begin until more than a century later. Germany established DST in May 1916, as a way to conserve fuel during World War I. The rest of Europe came onboard shortly thereafter. And in 1918, the United States adopted daylight saving time.

Though President Woodrow Wilson wanted to keep daylight saving time after WWI ended, the country was mostly rural at the time and farmers objected, partly because it would mean they lost an hour of morning light. (It's a myth that DST was instituted to help farmers.) And so daylight saving time was abolished until the next war brought it back into vogue. At the start of WWII, on Feb. 9, 1942, President Franklin Roosevelt re-established daylight saving time year-round, calling it "War Time."

After the war, a free-for-all system in which U.S. states and towns were given the choice of whether or not to observe DST led to chaos. And in 1966, to tame such "Wild West" mayhem, Congress enacted the Uniform Time Act. That federal law meant that any state observing DST — and they didn't have to jump on the DST bandwagon — had to follow a uniform protocol throughout the state in which daylight saving time would begin on the first Sunday of April and end on the last Sunday of October.

Then, in 2007, the Energy Policy Act of 2005 went into effect, expanding the length of daylight saving time to the present timing.

Why do we have daylight saving time?

Fewer than 40% of the world's countries observe daylight saving time, according to timeanddate.com. However, those who do observe DST take advantage of the natural daylight in the summer evenings. That's because the days start to get longer as Earth moves from the winter season to spring and summer, with the longest day of the year on the summer solstice. During the summer season in each hemisphere, Earth, which revolves around its axis at an angle, is tilted directly toward the sun.

Related: Read more about the science of summer.

Regions farthest away from the equator and closer to the poles get the most benefit from the DST clock change, because there is a more dramatic change in sunlight throughout the seasons.

Research has also suggested that with more daylight in the evenings, there are fewer traffic accidents, as there are fewer cars on the road when it's dark outside. More daylight also could mean more outdoor exercise (or exercise at all) for full-time workers.

The nominal reason for daylight saving time has long been to save energy. The time change was first instituted in the U.S. during World War I, and then reinstituted again during WW II, as a part of the war effort. During the Arab oil embargo, when Arab members of the Organization of Petroleum Exporting Countries (OPEC) stopped selling petroleum to the United States, Congress even enacted a trial period of year-round daylight saving time in an attempt to save energy.

But the evidence for any significant energy savings is slim. Brighter evenings may save on electric lighting, said Stanton Hadley, a now-retired senior researcher at Oak Ridge National Laboratory who helped prepare a report to Congress on extended daylight saving time. But lights have become increasingly efficient, Hadley said, so lighting is responsible for a smaller chunk of total energy consumption than it was a few decades ago. Heating and cooling probably matter more, and some places may need air-conditioning for the longer, hotter evenings of summer daylight saving time.

Hadley and his colleagues found that the four weeks of extra daylight saving time that went into effect in the United States in 2007 did save some energy, about half of a percent of what would have otherwise been used on each of those days, they said in a report to Congress published on Sept. 30, 2020. However, Hadley said, the effect of the entire months-long stretch of daylight saving could very well have the opposite effect.

A 1998 study in Indiana before and after implementation of daylight saving time in some counties found a small increase in residential energy usage. Temporary changes in Australia's daylight saving timing for the summer Olympics of 2000 also failed to save any energy, a 2007 study found.

Part of the trouble with estimating the effect of daylight saving time on energy consumption is that there are so few changes to the policy, making before-and-after comparisons tricky, Hadley told Live Science. The 2007 extension of daylight saving time allowed for a before-and-after comparison of only a few weeks' time. The changes in Indiana and Australia were geographically limited.

Ultimately, Hadley said, the energy question probably isn't the real reason the United States sticks with daylight saving time, anyway.

"In the vast scheme of things, the energy saving is not the big driver," he said. "It's people wanting to take advantage of that light time in the evening."

What places observe daylight saving time?

U.S. daylight saving time

Most of the United States and Canada observe DST on the same dates with a few exceptions. Hawaii and Arizona are the two U.S. states that don't observe daylight saving time, though Navajo Nation, in northeastern Arizona, does follow DST, according to NASA. The U.K. also observes daylight saving time.

Over the years, state legislatures have considered at least 450 bills to establish year-round daylight saving time, according to the National Conference of State Legislatures. And as of 2022, at least 19 states had introduced legislation to make standard time permanent, doing away with DST all together. However, the U.S. Congress would have to amend the Uniform Time Act (15 U.S.C. s. 260a) to authorize states this allowance, according to The New York Times.

Canada daylight saving time

Nine of Canada's 10 provinces observe daylight saving time. The provinces and territories in Canada that stay on standard time all year include: Some regions of the province of British Columbia, parts of Saskatchewan, northwest Ontario and east Quebec, according to timeanddate.com. Meanwhile, Yukon made DST permanent in 2020. In Saskatchewan, only Creighton and Denare Beach observe DST, according to timeanddate.com.

Starting in 2026, British Columbia will be moving to permanent daylight time, according to the CBC.

Europe daylight saving time

Most European countries observe DST, with the exception of Russia, Iceland and Belarus, according to timeanddate.com. In the United Kingdom, DST is called British Summer Time (BST).

DST is called Central European Summer Time (CEST) in: Austria, France, Germany, Italy, Hungary, Norway, Poland, Spain and Switzerland. Daylight saving starts at 2 a.m. local time for these countries, when clocks are moved ahead an hour to 3 a.m. The same 2 a.m. clock change is followed for Bulgaria, Estonia, Finland, Greece, Latvia, Lithuania and Romania, which call DST Eastern European Summer Time (EEST).

During summers in Ireland, DST is called Irish Standard Time (IST) and it begins at 1 a.m. local time, when clocks are moved ahead an hour to 2 a.m. The same clock change occurs in the Canary Islands, the Faroe Islands and Portugal, which call DST Western European Summer Time (WEST). However, even the European Union may propose an end to clock changes, as a recent poll found that 84% of 4.6 million people surveyed said they wanted to nix them, the Wall Street Journal reported. If the lawmakers and member states agree, the EU members could decide to keep the EU in summer time or winter time, according to the WSJ.

Southern Hemisphere DST

The DST-observing countries in the Southern Hemisphere — in Australia, New Zealand, South America and southern Africa — set their clocks forward an hour sometime during September through November and move them back to standard time during the March-April timeframe.

Australia, being such a big country (the sixth-largest in the world), doesn't follow DST uniformly: New South Wales, Victoria, South Australia, Tasmania and the Australian Capital Territory follow daylight saving, while Queensland, the Northern Territory (Western Australia) do not, according to the Australian government. In the observing areas, DST ends on the first Sunday in April — or April 5, 2026. It begins again on Sunday Oct. 4, 2026.

Daylight saving time myths

• Turns out, people tend to have more heart attacks on the Monday following the "spring forward" switch to daylight saving time. Researchers reporting in 2014 in the journal Open Heart, found that heart attacks increased 24% on that Monday, compared with the daily average number for the weeks surrounding the start of DST.
• Before the Uniform Time Act was passed in the United States, there was a period in which any place could or could not observe DST, leading to chaos. For instance, if one took a 35-mile bus ride from Moundsville, West Virginia, to Steubenville, Ohio, he or she would pass through no fewer than seven time changes, according to Prerau. At some point, Minneapolis and St. Paul were on different clocks.
• A study published in 2009 in the Journal of Applied Psychology showed that during the week following the "spring forward" into DST, mine workers got 40 minutes less sleep and had 5.7% more workplace injuries than they did during any other days of the year.
• Pets may notice the time change, as well. Since humans set the routines for their fluffy loved ones, dogs and cats living indoors and even cows are disrupted when, say, you bring their food an hour late or come to milk them later than usual, according to Alison Holdhus-Small, a research assistant at CSIRO Livestock Industries, an Australia-based research and development organization.
• The fact that the time changes at 2 a.m. at least in the U.S., may have to do with practicality. For instance, it's late enough that most people are home from outings and setting the clock back an hour won't switch the date to "yesterday." In addition, it's early enough not to affect early shift workers and early churchgoers, according to the WebExhibits, an online museum.

Additional resources

Teacher Planet has lots of worksheets and lesson ideas to help kids learn about daylight saving time. The History Channel has a 1-hour video on the history of daylight saving time. In this Smithsonian Magazine feature, you'll learn about a time when the U.S. had year-round DST.

Editor's note: This article is updated twice annually. It was last updated on March 5, 2026

The autumnal switch from daylight saving time (DST) to standard time comes with a surge of deer-vehicle collisions in the U.S., a new study suggests. The researchers argue that sticking with DST, permanently, could reduce the number of accidents, sparing the lives of dozens of people and tens of thousands of deer annually.

The new study, published Wednesday (Nov. 2) in the journal Current Biology, examined how switching to DST in spring and then turning the clocks back in fall might affect the rate of animal-related car crashes. Data from 23 states suggested that more than 90% of these crashes involve deer, most commonly either white-tailed deer (Odocoileus virginianus) or mule deer (Odocoileus hemionus), according to a statement.  

Deer tend to be most active around dawn and dusk, but according to the collision data, the risk of crashes jumps most significantly just after nightfall. Collisions occurred 2.3 times more frequently in the two hours after sunset than in the two hours before sunrise, and crashes were 14 times more frequent after sunset compared with two hours before sunset. 

Overall, the rate of deer-vehicle collisions peaks in autumn, "spiking in late October through November in all states analyzed except Alaska," the team wrote in their report. Roughly 10% of all the reported deer-vehicle collisions occurred in a two-week window after the "fall back" to standard time. Traffic volume data collected between 2013 and 2019 suggested that the time change comes with a sudden increase in the amount of driving after sunset, when deer-vehicle collisions are most likely.

Related: Why it's time to abolish daylight saving time 

This sharp increase in crashes mostly affects the East Coast, senior author Laura Prugh, an associate professor of quantitative wildlife sciences, told Science News. "In the western states, you also see an increase, but it's not nearly as sharp," she said. This is likely because the mating season, or "rut," for white-tailed deer peaks around the fall time change and the animals are more common on the East Coast than on the West Coast. Mule deer, which are more common in Western states, typically reach peak mating season later in the fall and early winter.

"We believe that this fall spike really happens due to the overlap of these two factors: the breeding season and the change from daylight saving time back to standard time," Prugh said in the statement. "We don't see a corresponding shift in deer-vehicle collisions in the spring during the other time change, and we believe that's in part because spring is not a breeding season for deer."

Prugh and her colleagues calculated that, if the U.S. switched to permanent DST, it could prevent about 2.3% of the 2.1 million deer-vehicle collisions that occur each year. That would prevent an estimated 33 human deaths, 2,054 human injuries, 36,550 deer deaths and $1.19 billion in costs annually, according to the statement. 

That said, the decrease in collisions would not be evenly distributed across all states, the authors wrote. The estimated change in the rate of crashes ranged from "an increase of 2.5% in Kansas to a decrease of 8.3% in Maine."

However, the reverse scenario — switching to permanent standard time — was projected to increase the number of collisions in every state, the team reported. In total, the team estimated that the switch would cause 73,660 more deer-vehicle collisions each year, leading to 66 additional human deaths, 4,140 more human injuries, 74,000 more deer deaths and an added $2.39 billion in costs annually.

When the U.S. Senate voted unanimously this spring to make daylight saving time permanent, the senators were said to be a little groggy, having just endured the clock's annual jump forward. Had they not lost an hour of sleep, clearer heads might've considered the science indicating daylight saving time is the one that needs nixing, putting the nation back on permanent standard time.

The bill stalled in the House of Representatives. So on Sunday, Nov. 6, states that observe the time changes will again fall back an hour, to standard time, and barring a legislative surprise they will spring forward again on the second Sunday next March.

Meanwhile, sleep experts and other scientists are calling for the end of daylight saving time (DST), saying clocks should be forever set on standard time — as happens in Hawaii, most of Arizona, and the U.S. territories. That would provide more hours of morning daylight, for adults and kids alike, thereby more properly setting the body's internal sleep-wake clock, called the circadian system.

"Daylight Saving Time disrupts the body's natural circadian rhythms and impacts sleep," Jennifer Martin, a clinical psychologist and president of the American Academy of Sleep Medicine, said in a statement. "Standard Time provides a better opportunity to get the right duration of high-quality, restful sleep on a regular basis, which improves our cognition, mood, cardiovascular health, and overall well-being." 

Related: Why daylight saving time starts Sunday

Anachronistic and unhealthy

The biannual time changes trace back to World War I and were aimed at saving fuel and lengthening the work day. But research suggests the changes don't save energy, and few folks seem to be craving longer work days. 

"The main problem with permanent Daylight Saving Time is that it causes more misalignment of our internal biological clock with the sun clock," said Kristin Eckel Mahan, associate professor and circadian rhythm researcher with McGovern Medical School at UTHealth Houston. "Our internal clock is better aligned with the sun clock when we are under Standard Time. This is particularly pronounced in the winter."

Switching permanently to Standard Time would mean people wake up in the dark, before sunrise, much less often than with the current time-change scheme or with a switch to permanent DST. 

Another way to look at it is this: Across the nation — from northern Washington state to southern Florida — 8 a.m. work (or school) start times would always occur after sunrise under permanent Standard Time. But under permanent DST, 8 a.m. would come before sunrise for long stretches during winter — anywhere from two to three months or more, depending on latitude and longitude.

To see the comparisons where you live, plug your own state and a nearby city into this sunrise chart. 

Why it matters

Natural, outdoor daylight, especially in the morning, is crucial to keeping your circadian system well-timed, said Dr. Nathaniel Watson, professor of neurology at the University of Washington School of Medicine and co-director of UW Medicine's Sleep Center. 

When this natural body clock is in sync with the sun, it suppresses production of the sleep-inducing hormone melatonin in the morning to help make you alert during the day, and then primes the release of melatonin as darkness sets in each evening. There's no set prescription for how much outdoor daylight you need, but some experts recommend at least two hours, if you can get it.

"There is no standard natural daylight exposure amount currently known to support optimal sleep and circadian health," Watson told Live Science by email. "Generally speaking, more is probably better."

Setting the clocks back an hour is an opportunity to grab some extra shut-eye, sure. But payback comes with the next jump forward, after which a slightly sleep-deprived population will endure its annual spike in car crashes and heart attacks.

"Switching between DST and Standard Time is not sustainable from a public health perspective," Randy Nelson, a professor and director of science research at West Virginia University's Rockefeller Neuroscience Institute, told me. "Essentially, the change to DST during the spring causes a misalignment between morning light and the circadian system. This misalignment is most noticeable acutely in the days following the change, but indeed persists for about eight months. Permanent DST would exacerbate this misalignment for 12 months."

Among the dozens of organizations that agree permanent Standard Time is the way to go are: 

• World Sleep Society
• European Sleep Research Society
• U.S.-based Sleep Research Society
• American College of Occupational & Environmental Medicine
• National Safety Council
• National PTA

Children and teens suffer from the weeks and months of dark mornings in the current setup, too. Kids might go from a dark house to a dark classroom and never get the melatonin-suppressing early morning daylight they need to avoid falling asleep at their desks, and which also preps them for a reasonable bedtime at night. "Instead, DST produces more nighttime light, which is not advantageous for sleep or health," Mahan explained by email.

What the people want

A majority of U.S. adults (63%) favor putting an end to the time changes, according to a 2020 poll. Support among Europeans is 84%. Whether people prefer Standard Time or DST as the new permanent standard, or if they even know which is which, was not surveyed. 

And no doubt many people might prefer having more daylight in the evening than in the morning, based on individual work or school schedules or other lifestyle factors. A friend of mine prefers making Daylight Saving Time permanent, "because I don't like it when it gets dark so early in the winter," he said, "and having the sunrise at 4:30 a.m. really is a waste of daylight for most of us."

Regardless, the United States remains stuck in a time warp for now, doomed to fall back and spring forward every year until Congress decides otherwise. Some members in the House are said to be considering the science, which helped stall the Senate bill. But at the time of writing, there's no movement on any time-change legislation.

Should you wish to see Standard Time become the default, the Save Standard Time advocacy group has a page full of suggested actions, including contacting lawmakers, writing a letter to the editor of your local paper, or spreading the word on social media. Or you could, like my friend, promote a different viewpoint.

Meanwhile, enjoy your extra hour this weekend. I suggest you sleep right through it.

It’s a question that’s been keeping (some of us) up at night: why do guys get sleepy after sex? Many men barely leave time for the bed sheets to settle before they make a beeline for the land of nod, but is there any scientific reason why one gender might be more predisposed to a post-sex snooze?

Well, there is, as it happens. Science journalist and author Melinda Wenner Moyer took a look at the possible factors that could play a part in this phenomenon.

For many women, the correlation between sex and snoring is one of those annoying facts of life: no matter when passionate encounters occur, men always seem to fall asleep immediately afterwards. Dave Zinczenko, the author of "Men, Love and Sex: The Complete User Guide For Women," explained the phenomenon to Huffington Post writer Arianna Huffington this way: "Men go to sleep because women don’t turn into a pizza."

I doubt I am ever going to become a pizza, and I’ll never have the foresight to order one beforehand. So in lieu of a cure, a better explanation will have to do. Although women sometimes feel sleepy after sex, the phenomenon does seem more pronounced in men. What is it, then, that spirals them into the land of nod?

First, the obvious reasons for sex’s somnolent sway: the act frequently takes place at night, in a bed, and is, after all, physically exhausting (often more so for the man than the woman, although this certainly varies). So when sex is over, it’s natural for a guy to feel sleepy.

Secondly, research using positron emission tomography (PET) scans has shown that in order for a person to reach orgasm, a primary requirement is to let go of "all fear and anxiety." Doing so also tends to be relaxing and might explain the tendency to snooze.

Then there is the biochemistry of the orgasm itself. Research shows that during ejaculation, men release a cocktail of brain chemicals, including norepinephrine, serotonin, oxytocin, vasopressin, nitric oxide (NO), and the hormone prolactin. The release of prolactin is linked to the feeling of sexual satisfaction, and it also mediates the "recovery time" that men are well aware of—the time a guy must wait before "giving it another go." Studies have also shown that men deficient in prolactin have faster recovery times.

Prolactin levels are naturally higher during sleep, and animals injected with the chemical become tired immediately. This suggests a strong link between prolactin and sleep, so it’s likely that the hormone’s release during orgasm causes men to feel sleepy.

(Side note: prolactin also explains why men are sleepier after intercourse than after masturbation. For unknown reasons, intercourse orgasms release four times more prolactin than masturbatory orgasms, according to a recent study.)

Oxytocin and vasopressin, two other chemicals released during orgasm, are also associated with sleep. Their release frequently accompanies that of melatonin, the primary hormone that regulates our body clocks. Oxytocin is also thought to reduce stress levels, which again could lead to relaxation and sleepiness.

What about the evolutionary reasons for post-sex sleepiness? This is trickier to explain. Evolutionarily speaking, a man’s primary goal is to produce as many offspring as possible, and sleeping doesn’t exactly help in his quest. But perhaps since he cannot immediately run off with another woman anyway — damn that recovery time! — re-energizing himself via sleep may be the best use of his time.

And although there is conflicting information as to whether women feel sleepy after sex, a woman often falls asleep with the man anyway (or uses it for some key cuddling time), which is good news for him: it means she is not off finding another mate. When the man wakes up and she’s still there, he just might be ready to go again.

It’s also possible that sleepiness is just a "side effect" associated with a more evolutionarily important reason for the release of oxytocin and vasopressin. In addition to being associated with sleep, both chemicals are also intimately involved in what is called "pair bonding," the social attachment human mates commonly share. The release of these brain chemicals during orgasm heightens feelings of bonding and trust between sexual partners, which may partially explain the link between sex and emotional attachment. This bond is favorable should the couple have a baby, as cooperative child rearing maximizes the young one’s chances for survival.

The bottom line is this: There are many potential biochemical and evolutionary reasons for post-sex sleepiness, some direct and some indirect — but no one has yet pinpointed the exact causes. One thing, however, is certain: we females better get used to it, because it doesn’t look likely to change anytime soon.

I will leave frustrated American women with one final thought: if you are upset at the ubiquity of the post-sex snoring phenomenon, remember that things could be a lot worse. A recent survey of 10,000 English men revealed that 48 percent actually fall asleep during sex.

Talk about coitus interruptus!

Originally published on Live Science on Feb. 1, 2013 and updated on Aug. 24, 2022. 

This answer was provided by Scienceline, a project of New York University's Science, Health and Environmental Reporting Program.

Don't forget to move your clock forward an hour overnight Saturday (March 12), as daylight saving time begins Sunday. And yes, this is the time change that takes an hour away from your day, but spring is on its way. 

Daylight saving time (not savings, as many people say) begins at 2 a.m. local time on Sunday, March 13. "Smart" devices may change time automatically, manual clocks don't, so make sure to move them an hour ahead, from 2 a.m. to 3 a.m. 

Why are we "springing forward" on Sunday? Daylight saving time (DST) is designed to provide an extra hour of evening sunlight, and so the clocks will remain in DST for eight months until Nov. 6, when daylight saving time ends for the year. 

The father of DST, Benjamin Franklin proposed the idea in 1784 as a way to conserve energy, said David Prerau, author of "Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time" (Thunder's Mouth Press, 2005). The idea was that people would spend that extra hour of daylight outdoors, rather than sitting inside, wasting energy on lighting and energy-sucking appliances, Franklin reasoned.

However, science has not provided absolute evidence to support the idea that  daylight saving translates into energy savings, according to several studies, including a 2007 Department of Energy study and a 1997 study on a residential home in Kansas, Live Science previously reported. Research published in November 2021 in the journal Energy Reports suggested the springtime clock changes did not equal energy savings; in that study, scientists examined energy consumption in Turkey before and after the country stopped following DST changes in 2016. The researchers noted the findings should also apply to the U.S. due to its location within a similar latitude range.

Even so, Franklin's idea spread in the 20th century. In 1908, a city in Ontario, Canada, became the first modern region to officially implement DST, according to timeanddate.com. The Germans began following DST in May 1916, with the goal of conserving fuel during World War I. The rest of Europe followed suit soon after, and the United States officially adopted daylight saving time in 1918.

However, American farmers objected to the change, since it eliminated an hour of their morning light; in fact, it's a myth that daylight saving time helps farmers. So, the country dropped the time change until World War II, and only a select number of states chose to follow it after the war's end.

Because daylight saving time was practiced at different times in different states, it threw the country's time zones into disarray. It wasn't until the Uniform Time Act of 1966 that daylight saving time acquired a standard start and stop time — although states themselves can choose whether to participate.

But why Sunday and why at 2 a.m.? That day and time were chosen to have the least impact on individuals. It’s late enough that most people will be home, and very few bars and restaurants should be impacted. In addition, when you move your clock at 2 a.m., you are not switching to another day; it would be confusing if the clock change occurred at say 11:30 p.m., because you would then be moving to the wee hours of the next day. The time switch also happens early enough that early-shift workers or churchgoers shouldn’t be impacted, according to the WebExhibits, an online museum.

Currently, two U.S. states — Hawaii and most of Arizona (with the exception of the Navajo Nation) — don't observe daylight saving time.

Every year, several states put forth bills or voter-led initiatives to ditch daylight saving time. However, it's anyone's guess whether these bills will become enforced law. Until then, don't forget to wake up an hour earlier on Sunday, unless you want to be late for brunch.

Editor's note: This article was first published in 2019 and updated on March 12, 2022. Originally published on Live Science.

The summer solstice, which marks the longest day of the year in the Northern Hemisphere, happens Sunday (June 20) at 11:32 p.m. EDT (Monday, June 21 at 03:32 UTC). This event happens when Earth's tilt toward the sun is at its maximum and the sun points directly over the Tropic of Cancer.

In other words, today is the day with the most amount of sunlight in the Northern Hemisphere. That extended daylight might make it difficult for people in northern latitudes to know when to go to sleep if they aren't looking at a clock, but the midnight sun is no problem for many other animals.

On this day, which provides a full 24 hours of daylight above the Arctic Circle, people in northern latitudes are celebrating with special events, like a live broadcast the moment the solstice begins at England's Stonehenge. But without a watch, people may ignore their bedtime, as humans are terrible at telling time during mostly light or mostly dark periods, according to a 1974 study in The Journal of Physiology. That's because light has a major effect on the human body's circadian rhythm, or sleep-wake cycle. 

Related: Photos: Stunning summer solstice photos

But many animals in northern latitudes can naturally control their sleep-wake cycles in extreme daylight conditions, said Cory Williams, a biologist at the University of Alaska Fairbanks. 

"There are animals that stop having a prolonged period of sleep," and they abandon their usual daily rhythm during this time of year, Williams told Live Science. For example, semipalmated sandpipers (Calidris pusilla) — small, brown-and-white shorebirds that breed above the Arctic Circle — are unfazed by the long periods of daylight. They alternate sleeping and waking hours with their nesting mate throughout the day. "When the male is active, the female is at the nest and vice versa," Williams said. "It's not on a 24-hour schedule."

Reindeer also ignore the absence of a light-dark cycle during the summer months. Instead, their sleep cycles are governed by ultradian rhythm, which means they sleep whenever they need to digest food. "They lose that long stretch of sleep they would normally have," Williams said. "They take lots of naps during the day instead of one concentrated bout of sleep.

This happens only in polar species, because their behavior is not entrained by light and dark cycles, Williams said. During this time of the year, the advantage for animals to be active at a particular time of day is lost. For instance, foraging at night doesn't save energy or provide protection from predators since it's daylight all the time.

But not all polar species abandon their circadian rhythm. For example, arctic ground squirrels (Spermophilus parryii) stick to their sleep schedules all year long. They retreat to their burrows during the darkest part of the day in the summer (which still isn't that dark, more like twilight) to save energy, Williams said.

Scientists such as Williams are still working to figure out what is different about polar animals that maintain entrained sleeping rhythms. As average global temperatures increase, animals are relocating to higher latitudes, Williams said, "so it will be interesting to see how animals that haven't been exposed to polar conditions will respond as they move north."

Editor's Note: This story was published June 21, 2018 and updated today with 2021 information.

Originally published on Live Science.

This Sunday, people across the United States can rest easy, literally, as they'll get an extra hour of sleep because daylight saving time comes to an end.

The change happens at 2 a.m. local daylight time on Nov. 3. While most wireless devices will "fall back" on their own, it's up to you to switch manual clocks — including those on microwaves, ovens and wristwatches — one hour back.

This means that as soon as the clock ticks to 2 a.m. on Sunday, it can be turned back to 1 a.m.

Daylight saving (not savings, as it's sometimes called) time won't start again until March 8, 2020, when the United States will, once again, "spring forward" an hour. [Daylight Saving Time 2018: A Guide to the When, Why, What and How]

Daylight saving time (DST) is the brainchild of Benjamin Franklin. The famous inventor and American politician reasoned that because the sun sets later in the spring and summer, Americans might save energy if they turned their clocks forward an hour, giving them an extra hour of natural light (no need to use artificial light), according to David Prerau, author of "Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time" (Thunder's Mouth Press, 2005).

However, it wasn't until 1916 that a country, Germany, implemented DST; the United States adopted it in 1918.

Moreover, it's unclear whether DST actually saves energy. Several studies, including a 1998 study in Indiana and a 2000 study in Australia, showed no energy savings from DST, Live Science previously reported. However, in 2018, researchers published a review of 44 studies looking at any link between DST and energy use. Their meta-analysis showed a slight decrease (0.34%) in electricity use on days where DST applied, according to their study published in The Energy Journal.

Regardless, DST persists despite dozens of bills introduced in state legislatures over the years to end it. Two states, Hawaii and Arizona, don't observe the time change, although Navajo Nation, in northeastern Arizona, does, according to NASA.

What's more, DST in the United States doesn't match up with clock changes in Europe, which stopped observing "summer time" for the year on Oct. 27. Europe will start following summer time again on March 29, 2020.

Daylight saving comes with its fair share of problems. A 2017 study in the in the Journal of Experimental Criminology showed that assault rates are higher on the Monday following the end of daylight saving time, compared with the Monday after that. Moreover, on the Monday following the spring time change, people are more likely to have heart attacks than on Mondays surrounding that date, another study found.

Traffic accidents also increase on the Mondays after both the fall and spring time changes, a 2001 study in the journal Sleep Medicine found.

However you spend your extra hour, remember this: Your pets don't know about the time change, so be kind to them: they may get hungry an hour earlier, Live Science previously reported.

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• Why Do People Get Sick When the Seasons Change?
• Why Do Some People Need Less Sleep Than Others?

Originally published on Live Science.

If you don't quite fit in among the morning people or night owls, well, you might soon have your own, more relatable, sleep category.

Now, researchers propose two more so-called chronotypes: the "afternoon" person and the "napper." A chronotype is defined by the time of day a person is most alert and sleepiest. [Top 11 Spooky Sleep Disorders]

A group of researchers in Belgium created and distributed a short online survey to over 1,300 people, ages 12 to 90, asking them questions about their sleep habits and tiredness levels throughout the day. They then analyzed the results in collaboration with a group in Russia.

They found that indeed there were 631 people who fit into one of the two well-known night and morning categories. While larks are wide awake in the morning and sleepier as the day progresses, owls are just the opposite.

But they also found, based on the wakefulness-sleepiness answers, that there were 550 participants (some of them repeats from the other two groups) that fell into one of two other groups, the nappers and the afternoon people.

Of all the chronotypes, afternoon people wake up the sleepiest and then they become alert around 11 a.m., staying that way until about 5 p.m., after which they get tired again. The "nappers" (so-called because they're prone to taking naps) wake up alert and stay alert until about 11 a.m., after which they get really tired until about 3 p.m. After 3 p.m. until about 10 p.m., they are alert and productive again, as was first reported by Psychology Today.

Still, the remaining 30% of participants didn't fall into any group.

Recognizing these categories is "important because some people can benefit from [an] afternoon nap and, you know, the conditions for an afternoon nap are not very good in the modern society," said lead author Arcady Putilov, a neurobiologist at the Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences in Moscow. Maybe if the nappers, for example, took a quick 10-15 minute snooze during the day, their performance would increase, he told Live Science.

The authors also found that the results, for the most part, held true in men and women, in both day- and night-shift workers and in all ages. There were some slight differences in age, such as older people tended to fall more into the "nappers" group. What's more, one limitation might be that most of the people who took the survey were younger-aged people in Belgium (half of the participants were under the age of 25). But still, Putilov thinks the findings would hold true in a broader sample.

The scientists reported their findings May 27 in the journal Personality and Individual Differences.

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Originally published on Live Science.

Some do it hanging upside down. Some do it for a few hours at a time. Some do it buried under a blanket of mud.

Regardless of their preferred mode, bats, elephants, frogs, honeybees, humans and more have something in common: They all sleep.

In fact, scientists have yet to find a truly sleepless creature. But is sleep really necessary for survival? [Why Do We Sleep?]

The dangers of sleeplessness

Most humans will acknowledge that sleep is absolutely necessary.

People often struggle to function after even just one sleepless night. Poor sleep over the long term has been linked to a host of negative health effects, from heart disease and stroke to weight gain and diabetes. These connections, and the fact that all animals seem to slumber, suggest that sleep must play an essential function for animals. But what is that function? Does sleep allow the brain to repair damage and process information? Is it necessary for energy regulation in the body? Scientists and thinkers as far back as the Greek philosopher Aristotle have offered explanations for why we sleep, and yet, the exact purpose of sleep remains an open question.

In the 1890s, Marie de Manacéïne, one of the first female physicians in Russia, was troubled by the mystery of sleep.

"We all love life, and we all wish to live as long as possible, but in spite of this, we sacrifice one-third, sometimes even half of our life in sleeping," Manacéïne once wrote. In her quest to figure out what exactly sleep is, she conducted the first sleep-deprivation experiment in animals.

Using an approach that now seems quite cruel, the physician kept puppies continuously awake, finding that they died after a few days of sleep deprivation. Over subsequent decades, further sleep-deprivation experiments using other animals, like rodents and cockroaches, found similarly fatal results. However, the underlying cause of death in these cases, and how it relates to sleep, is still unknown.

Super short-sleepers

While total sleeplessness seems dangerous, some creatures can get by with remarkably short bouts of sleep. They could be the key to understanding sleep's function, scientists have said.

A study published in February in the journal Science Advances monitored the sleeping habits of fruit flies.

"We found that some flies hardly ever slept," study co-author Giorgio Gilestro, a lecturer of systems biology at Imperial College London, told Live Science.

Gilestro and his colleagues observed that 6 percent of female flies slept for less than 72 minutes each day, compared to the average of 300 minutes that the other females slept. One female even slept as little as 4 minutes a day on average. In a further experiment, the researchers deprived the flies of 96 percent of their sleep time. But these flies didn't die prematurely, like the Russian puppies did; these virtually sleepless flies instead lived just as long as a control group that was left to sleep normally.

Now, Gilestro and a few other researchers are starting to wonder if sleep is less necessary than people have thought.

"Some animals seem to survive on far less sleep than previously expected based on restorative theories for the function of sleep," Niels Rattenborg, who studies sleep in birds at the Max Planck Institute for Ornithology in Germany, told Live Science.

In a 2016 study, Rattenborg and his colleagues outfitted great frigatebirds (Fregata minor) in the Galápagos Islands with a small device to measure electrical activity in the brain. The monitors showed that the birds sometimes slept in one hemisphere of their brains at a time while they were soaring over the ocean. They sometimes even slept in both hemispheres simultaneously while in flight.

Sleeping while flying could be common among other bird species — such as common swifts (Apus apus), which can fly for 10 months without landing — though scientists have no direct evidence for this.

But perhaps more surprisingly, the study found that the frigatebirds, while flying, slept on average just 42 minutes per day, even though they typically got more than 12 hours of shut-eye on land.

Does Rattenborg think we'll ever find an animal that doesn't sleep at all?

"Anything is possible," he said. "However, an emerging pattern among the studies of short-sleeping animals is that none are completely sleepless. This preservation of a little sleep suggests that there is a minimum amount of sleep that is essential, even in these remarkable short sleepers."

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Originally published on Live Science.

Not getting enough sleep is known to raise the risk of heart disease; now, a new study may have uncovered why a poor night's sleep is bad for your heart and blood vessels.

The study, conducted in mice, found that fragmented sleep alters the levels of a certain hormone, which in turn, increases production of inflammatory cells in the bone marrow. This inflammation plays a role in the development of atherosclerosis, or hardening of the arteries due to plaque buildup.

The findings, published today (Feb. 13) in the journal Nature, suggest that proper sleep "protects against atherosclerosis" and, conversely, that disrupted sleep makes the condition worse, the researchers said.

Still, because the study was conducted in mice, the findings need to be confirmed in people, the researchers said. [5 Surprising Sleep Discoveries]

Sleep and the heart

Numerous studies have linked not getting enough sleep with an increased risk of heart problems, including high blood pressure, heart disease, heart attacks and stroke, according to the Centers for Disease Control and Prevention (CDC). But the underlying biological reasons for this link have been unclear.

In the new study, the researchers looked at mice that were genetically prone to atherosclerosis. Some of the mice were allowed to get a sufficient amount of sleep, while others had their slumber frequently interrupted by a "sweep bar" that automatically moved across the bottom of the cage.

The sleep-deprived mice didn't experience any changes in weight or cholesterol levels compared with the sleep-sufficient mice. But the sleep-deprived mice did have larger plaques in their arteries and higher levels of inflammation in their blood vessels, compared with the sleep-sufficient mice, the study found.

The sleep-deprived mice also had lower levels of a hormone called hypocretin (also known as orexin) in a part of their brain called the hypothalamus. In humans, hypocretin is thought to promote wakefulness, and levels of the hormone are known to be reduced in people with the sleep disorder narcolepsy. Interestingly, some studies suggest that people with narcolepsy also have a higher risk of heart disease than people who don't have narcolepsy, the researchers noted.

The researchers found that the drop in hypocretin levels led to an increase in levels of a signalling protein called CSF1, which in turn increased production of inflammatory white blood cells in the bone marrow and accelerated atherosclerosis. What's more, restoring hypocretin levels in the mice reduced atherosclerosis.

"We have discovered that sleep helps to regulate the production … of inflammatory cells and the health of blood vessels and that, conversely, sleep disruption breaks down control of inflammatory cell production, leading to more inflammation and more heart disease," study senior author Filip Swirski, of the Massachusetts General Hospital Center for Systems Biology, said in a statement. "We also have identified how a hormone in the brain known to control wakefulness … protects against cardiovascular disease."

"We now need to study this pathway in humans" and explore other ways that sleep may affect heart health, Swirski said.

• Top 11 Spooky Sleep Disorders
• 5 Things You Must Know About Sleep
• 9 New Ways to Keep Your Heart Healthy

Originally published on Live Science.

Of all the modern inventions we rely on in our daily lives, the alarm clock is probably the most universally despised. Its jarring morning jangles jolt us uncomfortably out of our slumber, and back to reality. And yet however annoying alarm clocks are, they're also indispensable in getting us out of bed. That raises an interesting question: How did people wake up before alarm clocks became so ubiquitous?

Throughout the ages, even the simple act of telling the time has presented a huge challenge to humans that we've tried to solve with elaborate inventions. The ancient Greeks and Egyptians developed sundials and towering obelisks that would mark the time with a shadow that moved with the sun. Dating back to around 1500 B.C., humans produced hourglasses, water clocks and oil lamps, which calibrated the passing of hours with movements of sand, water and oil.

Out of these early inventions came a few rudimentary attempts to create a morning alarm — such as candle clocks. These simplistic devices from ancient China were embedded with nails that were released as the wax melted away, leaving the nails to clatter loudly into a metal tray below at a designated time, waking the sleeper. [Why Can't We Remember Our Dreams?] 

But such crude inventions were unpredictable and unreliable. And so, until more precise mechanical inventions were created, humans had to depend on another more innate form of timekeeping: our own internal body clocks.

Humans have two biological processes that underlie our natural sleeping and waking patterns: homeostasis and circadian rhythms, said Melinda Jackson, a senior research fellow in sleep and psychology at the Royal Melbourne Institute of Technology University in Australia. The main principle underlying homeostasis — a signaling process that's governed by the hypothalamus region in the brain — "is that the longer we are awake, the higher our drive for sleep or likelihood of falling asleep [is]," Jackson told Live Science. Then, "when we fall asleep, the drive for sleep dissipates across the night" — which signals when it's time to wake up, she said.

Overlaying this, the circadian rhythm — also controlled by cells in the hypothalamus — is a parallel process that regulates phases of sleepiness and alertness over the course of a day. This process is also affected by light and dark, meaning that periods of alertness and sleepiness usually correspond with morning light and nighttime darkness, respectively. In an era before alarms, Jackson says it's probable that this is how people woke up, cued by the accumulated hours of sleep, paired with the rays of the rising sun.

Religious cues

In her research on Britain's historical sleeping practices, Sasha Handley, a senior lecturer in early modern history at the University of Manchester in the United Kingdom, has discovered that people during this Christian era would often orientate their beds toward the east — where the sun rose. Their reasoning was partly religious, because the east was believed to be the direction from which Jesus would come during his resurrection, she said. But it's possible that this orientation also enabled people to wake with the sun's rays.

"It's hard to imagine now a world where your patterns of sleeping and waking up again were directly influenced by the setting and rising of the sun," Handley told Live Science.

Another simple, but notable fact is that the people of yore had no way of soundproofing their houses against the noises of the outside world, like we do today, Handley added. "For a society that was overwhelmingly agriculture before the Industrial Revolution, noises of nature were probably really important things," she said. The sounds of roosters crowing and mooing cows waiting to be milked would have interrupted people's slumber. Church bells also functioned as a type of early alarm clock, she said. [How Does an Atomic Clock Work?]

Handley thinks that historically, people may also have been more personally motivated to wake up at a particular hour. Research on early modern Britain shows that during this era, the morning hours were seen as a spiritual time, when one's closeness to God could be demonstrated by waking up at a scheduled time to pray. "Waking up in a scheduled way was seen to be a sign of health and good ethics," Handley said. "There's almost a sense of competitiveness that underpins this: The earlier you got out of bed, the more God had favored you with physical strengths." 

Peashooters

But by the 1600s and into the 1700s, self-reliance for waking probably became less crucial with the spread of the first domestic alarm clocks, known as lantern clocks, driven by internal weights that would strike a bell as an alarm. In 1800s Britain, wealthier families would also employ knocker-uppers — people armed with long sticks they used to tap incessantly on someone's window until they were roused. (Some knocker-uppers even used straws through which they would shoot peas at their clients' windows.) These human timekeepers were gradually replaced by the spread of cheap alarm clocks in the 1930s and 1940s — the precursors to those we know today.

But is our modern-day dependence on alarms actually a good thing? Jackson isn't so sure. The fact that nowadays we tend to take the opportunity on weekends to sleep in is "an indication that people need to make more time for sleep during the week by going to sleep earlier at night, but we don't do this," she said. Instead, we're working later and longer than ever, and our evenings are invaded by televisions, laptops and mobile phones. "Sleep is not prioritized," Jackson said. "So, we don't have much choice other than to use an alarm."

In this regard, Handley thinks history may offer a few lessons. During early modern history, there's evidence that people attached great importance to the health benefits of sleep. "Sleeping well is a really essential part of their regular health care practices," Handley said.

Nighttime was highly ritualized: People consumed soporific herbal drinks, stuffed their pillows with soothing scented flowers and engaged in calming activities like prayer and meditation or in mindless hobbies such as embroidery right before bed.

If we were to take some advice from these historic humans, Handley said it would be to "put sleep back at the center of your 24-hour cycle. Treasure it and revel in it. It is the single best thing you can do for yourself." As an added bonus, waking up wouldn't be such a drag.

Originally published on Live Science.

This story was updated at 10:45 a.m. ET on Oct. 18.

A new, limited-time-only burger at Burger King has a peculiar selling point: It's supposed to give you nightmares.

Yes, Burger King's Halloween-themed "Nightmare King" burger is allegedly "clinically proven" to induce nightmares, according to a press release from the company.

The fast-food chain commissioned a sleep study to bolster their claims that the green-bunned burger causes bad dreams. Needless to say, that study hasn't been published in a peer-reviewed journal. And what little peer-reviewed data there is on food and nightmares suggests that, if anything, fast food should, in fact, reduce bad dreams. [11 Ways Processed Food Is Different from Real Food]

Marketing with science?

To show that its Halloween concoction actually causes nightmares, Burger King commissioned Florida Sleep and Neuro Diagnostic Services Inc. to track the sleep and dreams of 50 people, 25 of whom ate the chicken-beef-bacon Nightmare King before bed and 25 of whom did not. Seven of the participants who ate the sandwich reported nightmares, compared with two who didn't eat the sandwich, according to a publicist for Burger King.  

"According to previous studies, 4 percent of the population experiences nightmares in any given night," Dr. Jose Gabriel Medina, a sleep specialist who led the study, said in the company's statement. "But [for people who slept] after eating the Nightmare King, the data obtained from the study indicated that the incidence of nightmares increased by 3.5 times."

Burger King attributed this spooky effect to the burger's "unique combination of proteins and cheese," which the company says disrupt a person's rapid eye movement (REM) sleep. This is the part of sleep when most dreaming occurs.

Dreams and diet

So, what does the scientific community say about fast food and dreams? Not much. There are very few studies on diet and dreams. But research does suggest that, if anything, fast food suppresses nightmares.

A 2007 study in the journal Psychological Reports asked approximately 50 undergraduates to report their dreams and their food preferences. People who reported preferring fast food, chips and other carbs were less likely to report remembering their dreams at all compared to people who liked organic food. A larger, 2015 study in the journal Frontiers in Psychology asked almost 400 students about sleep and food, finding that people who reported unhealthy diets also reported relatively few vivid dreams.

For nightmares, specifically, the 2015 study found no link between diet and bad dreams. The 2007 study found that people who reported liking junk food more had fewer nightmares. [7 Mind-Bending Facts About Dreams]

On the other hand, there is some evidence that fasting leads to more-vivid dreams, according to the 2015 study. Participants in that study who reported going longer between meals or snacks during the day also reported more-vivid dreams. This result could be due to the effects of fasting on the brain, the researchers wrote. Or it could that the people who skipped meals did so because they were sleeping late in the morning, which allowed them to squeeze in extra REM sleep.

More general eating patterns might influence dreams, said Tore Nielsen, a psychologist who researches dreams at the University of Montreal and the co-author of the 2015 study. People who report binge-eating or emotional eating also reported more disturbed dreams in that survey, Nielsen told Live Science. (It's possible that the underlying emotions that drive these eating patterns also drive bizarre or scary dreams.)

Still, many people do believe that certain foods, particularly spicy foods or cheese, cause bad dreams, Nielsen and his colleagues found. Indeed, 11.5 percent of participants in that study said they thought their dreams were affected by eating specific foods. Some foods do contain nutrients that can theoretically affect sleep, the researchers wrote, so perhaps these participants were correct.

But, the researchers added, the foods could also be causing gastrointestinal upset that resulted in disturbed sleep and disturbed dreams. Or, the scientists wrote, it's possible that people simply attributed their random bad dreams to food because they already believed in the folklore that links the two.  

At any rate, Burger King isn't the only commercial interest that has tried to lure consumers with the promise that a product will infiltrate their dreams. In 2005, the British Cheese Board produced a study claiming that cheese doesn't give people nightmares. Different kinds of cheese prompted different kinds of dreams, according to the study. Cheddar eaters, for example, enjoyed dreams of celebrities.

Like Burger King's, that study was never published in a peer-reviewed journal. Unfortunately for science, it also failed to investigate the Nightmare King's crowning ingredient, American cheese.    

Editor's Note: This story was updated on Oct. 18 to include more thorough information about the Nightmare King study from Burger King's publicist, as well as information on the association between emotional eating patterns and dreams.

Originally published on Live Science.

Enjoy dreaming? Two key genes may be to thank. A new study in mice finds that these "dream genes" are essential to that phase of slumber that brings people bizarro-world visions of taking high school math tests naked, losing teeth and soaring through the air.

Without the genes, called Chrm 1 and Chrm 3, mammals would not experience rapid eye movement (REM) sleep, during which the brain is as active as it is during wakefulness but the body is paralyzed. The discovery is important, researchers said, because poor sleep and psychiatric disorders are linked. So, understanding the basic control of sleep in the brain could refine pharmaceutical treatments for both sleep and psychiatric problems, said study leader Hiroki Ueda of Riken, a Japanese research institute.

"Sound sleep is essential to the quality of human life, while some impairment in sleep may lead to various untoward consequences," Ueda told Live Science in an email. But the "molecular machinery [of sleep] largely remains to be revealed, hindering the development of treatments for sleep-related diseases." [5 Surprising Sleep Discoveries]

Strange cycle

In a given night, humans cycle through non-REM and REM sleep, which are defined by different patterns of brain activity. No one knows the precise reason for these different sleep phases, but problems with REM sleep have been linked to dementia, Parkinson's disease and other neurological disorders. And poor sleep in general is linked with an increased risk of suicide.

That's why Ueda and his colleagues are interested in understanding the basics of how sleep works. Scientists have already discovered that the transition from non-REM to REM sleep involves a neurotransmitter called acetylcholine. But there are 16 types of cellular receptors in the brain that acetylcholine can bind to, and it was far from clear which were essential to REM sleep and which were redundant.

To find out, the researchers used CRISPR technology to knock out the genes for these acetylcholine receptors, one by one, in mice. CRISPR uses a genetic sequence to guide an enzyme to the desired section of DNA, where the enzyme then snips the sequence, preventing that gene from being expressed.

Losing sleep

The study immediately showed that one family of acetylcholine receptors, the nicotinic type, didn't have much to do with sleep. Mice deprived of those receptors slept more or less like mice that had them.   

The other family, muscarinic acetylcholine receptors, turned out to be much more interesting. Specifically, the loss of two receptors called Chrm1 and Chrm3 shortened sleep by close to 3 hours a day. Losing either one of the two receptors reduced and fragmented REM sleep specifically, while also reducing non-REM sleep. And mice with neither receptor basically didn't experience REM sleep at all. [Top 11 Spooky Sleep Disorders]

Strangely, those REM-free mice survived without this dreamy sleep state, despite hypotheses that REM sleep is necessary for survival. That's an interesting avenue for further research, Ueda said, but it could be an unintended side effect of working with lab animals in an artificial environment.

The "mutant mice can survive in a laboratory condition with a lot of food and without any [enemies]," Ueda told Live Science. "In a wild environment, these genes would be important for the survival of organisms."

Understanding the specific receptors that control sleep can inform new treatments for psychiatric disorders like depression and post-traumatic stress disorder, which is often marked by vivid nightmares, Ueda said. The researchers found subtle differences in the way Chrm1 and Chrm 3 work, he added, so the team is interested in taking a closer look at what happens when these receptors are triggered. And because the research was done in mice, more work is needed to study how these genes work in humans.

"This investigation may help molecularly define REM sleep and may reveal the physiological roles of REM sleep in its closely related higher cognitive functions, such as learning and memory," Ueda said.

The study was published yesterday (Aug. 28) in the journal Cell Reports.

Originally published on Live Science.

Here's something to expect when you're expecting: hearing the phrase "Sleep while you can" repeated by every person you meet for 40 weeks.

For pregnant mothers, that's easier said than done — especially if they're fond of sleeping on their backs or bellies. Currently, many doctors tell pregnant women to sleep exclusively on their left sides at night. But why? What's so bad about resting on the right or snoozing in a supine position?

Turns out, there's a good medical reason for it, and it involves an unseen Tetris game happening inside every pregnant woman's belly. [18 Ways Pregnancy May Change Your Body Forever]

A prenatal puzzle

As a fetus grows larger and larger throughout gestation, it naturally begins to put more and more pressure on mama's internal organs and blood vessels. It can be annoying or painful when the growing baby plops onto mama's bladder or kicks her in the intestines. But comfort isn't behind the prescription for left-side sleeping. According to Dr. Grace Pien, an assistant professor of medicine at the Johns Hopkins University School of Medicine, the crucial piece of the puzzle is the mother's inferior vena cava (IVC), a large vein that runs along the right side of the spine and is responsible for returning blood from the bottom half of the body to the heart.

"If a pregnant woman is lying on her back, the fetus is more likely to compress the inferior vena cava, decreasing the amount of blood returned to the heart," Pien told Live Science. "There's not a lot of research comparing sleeping on the right and left side, but at least theoretically, you'd also have less potential compression of the IVC on your left side than on your right."

Why is this compression bad? Less blood being pumped into the heart means less blood being pumped out of the heart — and that means a drop in blood pressure for mom, and a drop in blood oxygen content for both mom and baby. (Mom's blood carries oxygen to the baby.) Most healthy women and fetuses should be able to compensate for a slight reduction in cardiac output, Pien said, but IVC compression can become a bigger risk for pregnant women who already have blood pressure problems or breathing complications.

For example, pregnant women with asthma or sleep apnea (a condition in which breathing repeatedly starts and stops at night) may already have trouble delivering the optimal amount of oxygen to their bodies or their babies. When conditions like these are coupled with the reduced blood flow that comes from supine sleeping, the effects could magnify each other in a dangerous way.

"A number of studies have suggested that sleeping on one's back during late pregnancy may be associated with a higher risk for stillbirth," Pien said.

The evidence for this connection is mounting. Most recently, a study published earlier this year in BJOG: An International Journal of Obstetrics and Gynaecology found that women who had a stillbirth after 28 weeks gestation were 2.3 times as likely to have slept on their backs the night before the stillbirth than women with a healthy continuing pregnancy. Another study, published in the journal PLOS One in 2017, found supine sleeping was associated with a 3.7 times higher risk of stillbirth than is found overall. One limitation to keep in mind for studies like these — where people are asked to recall what they did in the past — is something called "recall bias." With recall bias, women who had a bad outcome, such as a stillbirth, are more likely than women with a healthy pregnancy to rack their brains for anything they may have done to cause it.

These alarming trends have been repeated often enough that most doctors don't hesitate to recommend that pregnant women avoid sleeping in the supine position. It is, as Pien put it, "a relatively easy, cost-free intervention" that can potentially prevent some very negative pregnancy outcomes.

What's wrong with right?

So, what — if anything — is wrong with sleeping on the right? That's hard to say, as there haven't been many studies specifically comparing left- and right-side sleeping during pregnancy. One study of 155 women, published in the journal The BMJ in 2011, did find a slightly increased risk of stillbirth in women who went to bed on their right rather than their left the night before they miscarried, but these results have not yet been repeated.

"I don't think there's clear evidence that sleeping on your right is worse than sleeping on your left," Pien said. "If there's a reason somebody is sleeping on their right because they're more uncomfortable sleeping on their left, I don't think there's a reason not to do it."

If you have an otherwise healthy pregnancy and absolutely can't sleep on your left, rolling over to the right is probably nothing to worry about, Pien said. In fact, it might be better for you; not getting enough sleep may be much worse for pregnancy outcomes than the slight risk of IVC compression when lying on your right flank.

"Research suggests that pregnant women who are not getting enough sleep — less than 5 or 6 hours of sleep a night — probably are at increased risk for things like gestational diabetes, and potentially for things like preeclampsia," Pien said. "Getting enough sleep is very important to pregnancy."

Enjoy it while you can.

Originally published on Live Science.

Getting too little sleep is tied to a slew of ill health effects, and now, researchers say sleep deprivation could contribute to loneliness as well. And this loneliness could be "contagious."

A small new study suggests that when people are sleep-deprived, they feel lonelier and are more inclined to keep a greater physical distance from others, compared with when they are fully rested.

What's more, sleep-deprived people may give off a lonely vibe; they are judged by others to be lonelier and less socially "attractive," compared with fully rested people, the researchers said. This could lead to a "vicious cycle" that perpetuates loneliness, the investigators said. [5 Surprising Sleep Discoveries]

Surprisingly, the lonely feeling tied to sleep deprivation may also be socially "contagious." The study found that when well-rested people had a brief encounter with a sleep-deprived person, the well-rested people reported feeling lonelier themselves. This suggests there may be a "viral contagion of social isolation" linked to sleep loss, the researchers wrote in the study, published today (Aug. 14) in the journal Nature Communications.

The researchers said the findings raise the question of whether concurrent increases in sleep deprivation and loneliness in populations in developed countries are related.

"It's perhaps no coincidence that the past few decades have seen a marked increase in loneliness and an equally dramatic decrease in sleep duration," lead study author Eti Ben Simon, a postdoctoral fellow at the Center for Human Sleep Science at the University of California, Berkeley, said in a statement. "Without sufficient sleep, we become a social turnoff, and loneliness soon kicks in."

Sleepy and lonely

The study involved a series of experiments conducted both in a laboratory and online, using surveys.

For the lab studies, the researchers tested 18 healthy young adults after they'd had a normal night's sleep and again after they were deprived of sleep for an entire night.

For the tests, first, the participants performed something called a "social distance task," in which a person walked toward them, and the participants told the walker to "stop" when they got too close for comfort (or when they got to the distance the participants would normally keep between themselves and a stranger). Participants also performed a similar task while they had their brains scanned and watched a video of a person walking toward them.

During both the in-person and video task, participants kept people at a greater "social distance" if they were sleep-deprived, compared to when they were well-rested. The social distance that a person felt comfortable with increased by about 13 to 18 percent when that individual was sleep-deprived, the researchers found.

In the brain scan, the researchers found that when people were sleep-deprived, they had increased brain activity in an area called the "near-space network." This area is thought to be active when people perceive potential incoming threats from others.

In contrast, in an area of the brain called the "theory of mind" network, which is thought to encourage social interaction, activity was decreased when participants were sleep-deprived.

To see if these findings might translate to the real world, the researchers had about 140 people track their sleep for two nights using sleep logs to note about how long it took them to fall asleep and how long they stayed asleep.

People who reported poor sleep from one night to the next also reported an increase in feelings of loneliness the next day, while those who got better sleep reported reduced loneliness, the researchers found.

Is loneliness contagious?

Finally, the researchers wanted to see how other people viewed those who didn't get enough sleep. The scientists had about 1,000 people watch videos of the lab participants being interviewed when they were sleep-deprived or well-rested.

The viewers rated participants as appearing lonelier, and less like a person they would want to interact or collaborate with, if they were sleep-deprived compared with if they were well-rested.

And the researchers were also surprised to find that the viewers reported feeling lonelier themselves after watching an interview with a sleep-deprived person.

Overall, "this all bodes well if you sleep the necessary 7 to 9 hours a night, but not so well if you continue to short-change your sleep," said senior study author Matthew Walker, a UC Berkeley professor of psychology and neuroscience. "On a positive note, just one night of good sleep makes you feel more outgoing and socially confident and, furthermore, will attract others to you," Walker said.

The researchers noted that changes in people's mood and feelings of anxiety that increased when people were sleep-deprived could have affected the results. However, using statistical methods, the researchers found that their results held even after taking into account these changes. The findings suggest that sleep loss contributes to feelings of loneliness, independent of these other emotions, the scientists said.

However, participants in the study were all young adults ages 18 to 24, and future studies should examine how the link between sleep loss and loneliness changes over the human life span, the researchers said.

Original article on Live Science.

Scorching summer days can be tough without air conditioning, and you might find yourself searching for ways to stay cool, including using a fan at night. But is it healthy to sleep with a fan on?

Some recent headlines have made sleeping with a fan on sound downright dangerous. "Why Sleeping with Your Fan on Could Be Seriously Damaging Your Health," read one recent headline from the Mirror. "Sleeping with a Bedside Fan Could Pose Health Risks," read another, from LifeZette.

But experts say the reality is not that dire.

"There's nothing about a fan that's toxic," said Dr. Len Horovitz, a pulmonologist at Lenox Hill Hospital in New York City. "There's nothing wrong with circulating air." [7 Common Summer Health Concerns]

Indeed, sleep is very important, and you don't want to be sweating all night, Horovitz told Live Science.

But anything that causes rapid air movement, including a fan, can evaporate moisture from your mouth and nasal passages, drying them out, he said. Fans may also circulate dust, which could bother people, particularly if they have allergies.

If you do sleep with a fan on, Horovitz said it's a good idea to keep it at a safe distance from your bed and not have it blowing right on you. To guard against dust and other allergens, Horovitz recommended keeping an air filter in the bedroom. He also recommended performing daily sinus irrigation with saline, which can help with dry nasal passages, congestion and other nasal problems.

Cold air can also cause muscle contractions, and so exposure to this air at night may lead to a stiff neck in the morning. But Horovitz said this is more of a problem with air conditioning that's left on at night than it is with fans. If you do sleep with air conditioning on at night, Horovitz said the air shouldn't be blowing directly on you and the setting shouldn't be lower than 68 degrees Fahrenheit (20 degrees Celsius).

Original article on Live Science.

You spend a third of your life asleep, a good chunk of which involves dreaming. But most often, you don't remember any of your dreams. And even on those lucky days when you wake up with a memory of the dream still floating in your mind, there's a good chance that in just a minute the memory will vanish into thin air and back to dreamland.

In waking life, such a case of quickly forgetting recent experiences would surely land you in a doctor's office. With dreams, however, forgetting is normal. Why?

"We have a tendency to immediately forget dreams, and it's likely that people who rarely report dreams are just forgetting them more easily," said Thomas Andrillon, a neuroscientist at Monash University in Melbourne, Australia. It might be hard to believe that you had a dream if you don't remember anything, but studies consistently show that even people who haven't recalled a single dream in decades or even their entire lifetime, do, in fact, recall them if they are awakened at the right moment, Andrillon said. [Can I Control My Dreams?] 

While the exact reason is not fully known, scientists have gained some insight into memory processes during sleep, leading to several ideas that may explain our peculiar forgetfulness.

You are awake, but is your hippocampus?

When we fall asleep, not all the brain's regions go offline at the same time, according to a 2011 study in the journal Neuron. Researchers have found one of the last regions to go to sleep is the hippocampus, a curved structure that sits inside each brain hemisphere and is critical for moving information from short-term memory into long-term memory.

If the hippocampus is the last to go to sleep, it could very well be the last to wake up, Andrillon said. "So, you could have this window where you wake up with a dream in your short-term memory, but since the hippocampus is not fully awake yet, your brain is not able to keep that memory," Andrillon told Live Science.

While this might explain why dream memories are so fleeting, it doesn't mean that your hippocampus has been inactive throughout the night. In fact, this region is quite active during sleep, and appears to be storing and caring for existing memories to consolidate them, instead of listening for incoming new experiences.

"Some data shows that [during some sleep stages] the hippocampus is sending information to the cortex, but not receiving any," Andrillon said. "This unidirectional communication would allow sending memories from the hippocampus to the brain's cortex for long-term storage, but new information wouldn't be registered by the hippocampus."

Upon awakening, the brain may need at least 2 minutes to jump-start its memory-encoding abilities. In a 2017 study published in the journal Frontiers in Human Neuroscience, researchers in France monitored sleep patterns in 18 people who reported remembering their dreams almost every day, and 18 others who rarely remembered their dreams. The team found that compared with low-dream recallers, high recallers woke up more frequently during the night. These middle-of-the-night awakenings lasted an average of 2 minutes for high recallers, whereas low-recallers' awakenings lasted for an average of 1 minute. [What Do Babies Dream About?]

Neurochemical soup

Our poor ability to encode new memories during sleep is also linked to changes in the levels of two neurotransmitters, acetylcholine and noradrenaline, which are especially important for retaining memories. When we fall asleep, acetylcholine and noradrenaline drop dramatically.

Then, something strange happens as we enter the rapid eye movement (REM) stage of sleep, where the most vivid dreams occur. In this stage, acetylcholine returns to wakefulness levels, but noradrenaline stays low.

Scientists have yet to work out this puzzle, but some suggest that this particular combination of neurotransmitters might be the reason we forget our dreams. The boost in acetylcholine puts the cortex in an aroused state similar to wakefulness, while low noradrenaline reduces our ability to recall our mental escapades during this time, according to a 2017 study in the journal Behavioral and Brain Sciences.

Sometimes your dreams are just not memorable

Do you remember what you were thinking about this morning when brushing your teeth? Our minds wander all the time, but we discard most of those thoughts as nonessential information. Dreams, especially mundane ones, may be just like daydreaming thoughts and deemed by the brain to be too useless to remember, the late dream researcher Ernest Hartmann, who was a professor of psychiatry at Tufts University School of Medicine, wrote in Scientific American.

But dreams that are more vivid, emotional and coherent seem to be better remembered — perhaps because they trigger more awakening, and their organized narrative makes them easier to store, Andrillon said.

If you are intent on improving your dream recall, there are a few tricks to try. Robert Stickgold, an associate professor of psychiatry at Harvard Medical School, suggests drinking water before bed, because it will make you wake up at night to use the bathroom. These "middle-of-the-night awakenings are frequently accompanied by dream recall," Stickgold told The New York Times.

Once in bed, repeatedly reminding yourself that you want to remember your dreams may increase your chances, and so does keeping a dream journal, some studies have suggested. Upon waking up, hang on to that fragile dream memory: Keep your eyes closed, stay still and replay the dream memory, until your hippocampus catches up and properly stores the memory.

Original article on Live Science.

Not getting enough sleep can be detrimental to your health; many studies even link the lack of Z's to higher odds of dying during a certain time period. But a new study from Sweden suggests that if you can't sleep as much as you need during the week, you may be able to make up for it on the weekends.

The researchers found that people ages 65 and under who slept 5 hours or less a night had a 65 percent higher risk of death during the 13-year study period than those who got 6 or 7 hours of sleep a night. But individuals who balanced their short weekday sleep with longer weekend sleep did not appear to have any increased mortality risk.

The findings suggest, in other words, that you may be able to make up for the damaging effects of lost sleep. [5 Surprising Sleep Discoveries]

"We can't really say 100 percent we have proven this, but it's a reasonable assumption that this is what's happening," said lead study author Torbjörn Åkerstedt, a professor of behavioral medicine at Stockholm University in Sweden.

The study was published today (May 23) in the Journal of Sleep Research. Previous studies looking at sleep deprivation and mortality risk often asked participants about their "usual" sleep duration, which is often interpreted as one's weekday sleep schedule. But "we suspected that might not be the whole story," Åkerstedt told Live Science.

In the study, Åkerstedt and his colleagues gathered the data of more than 38,000 adults, collected in a medical survey in Sweden in 1997. In the survey, the participants answered two questions about their sleep duration, on weeknights and on days off.

The team then tracked the participants for up to 13 years, using the country's national death register, and controlled for factors that can contribute to health or mortality risk, such as gender, body mass index and smoking.

Just as previous studies have shown, sleep duration had a U-shape relationship with mortality risk. In other words, both too much and too little sleep were linked to risk of death during the study period. Like people who slept less than 5 hours a night, people who consistently slept 8 or more hours fared worse than those who slept 6 or 7 hours a night.

Short sleep duration has been linked to numerous health problems, including stroke, heart disease, metabolic syndrome, hypertension and obesity, all of which increase the risk of death. But the link between long sleep duration and mortality risk is more mysterious, and may be driven by a third factor, such as an underlying health problem that is not measurable, Åkerstedt said.

"With long sleep we don't have a good explanation. We think there has to be something going that has to do with higher need for sleep and is not healthy," he said. In other words, an underlying health problem may be the reason a person is sleeping too much.

The study also found that the link between sleep patterns and mortality disappeared for those ages 65 or older. "At that age, people get the sleep they need, whereas for a 30- or 40-year-old, there's often a huge discrepancy between the sleep they need and what they actually get," Åkerstedt said.

Although the consequences of this discrepancy can be mitigated with a weekend sleep-in, there may be a limit. Studies have found that sleep deprivation induces physiological changes, such as loss of neurons and alterations in brain connectivity, that could be potentially long term.

In addition, losing just 1 hour of sleep may have different effects on the body than losing several hours. "You are much more hit by an all-nighter than a half-nighter," Åkerstedt said.

Original article on Live Science.

Our memory is imperfect: We remember some moments but lose others like a problematic tape recorder. Sometimes, we even "remember" things that never happened — a phenomenon that researchers call "false memory" (and a reason why eyewitness testimonies can be misleading).

But where do these false memories come from? Previous studies have suggested that sleep plays a role in the formation of false memories, and in a recent small study, researchers homed in on one particular aspect of sleep, called sleep spindles, as the potential culprit.

Sleep spindles are quick bursts of brain activity during sleep, according to the study, which was published in December in the journal Neuropsychologia. They occur in one of the lighter stages of sleep, called Stage 2, which is defined by a slowed heart rate and no eye movement.

To study how sleep spindles may play a role in the formation of false memories, the researchers recruited 32 well-rested, non-caffeinated university students. The participants were shown a handful of words — all related to the same topic — before being hooked up to a polysomnography device, which monitors brain activity during sleep. The participants were then randomly assigned to one of two groups: a napping group or an awake group. The napping group was sent to a room with a bed and blackout blinds, while the awake group was told to watch a nature documentary or a Mr. Bean cartoon. The polysomnography device recorded brain activity to make sure the napping group was actually asleep and not just lying in bed.  [5 Surprising Sleep Discoveries]

After their respective activities, all of the participants were again shown a series of words and were asked if they had seen the words before. Some of the words were repeats from the first session, but some were new. What's more, the researchers threw in some "lure" words that were related to the topic of all the words but weren't shown to the participants before.

The researchers found that the students who napped were significantly more likely to fall victim to "lure" words and say that they had seen the words before, creating false memories. The findings were what the researchers had predicted based on previous studies.

Right vs. left

But the researchers also wanted to test if one side of the brain was more gullible than the other. To do so,  the researchers designed the experiment so that the words flashed on the screen far to the left or far to the right in a visual field available to only one brain hemisphere at a time. If you blinked, you missed the word, said lead study author John Shaw, a psychology doctoral student at Lancaster University in England. But this wasn't to be annoying, he added; if the words stayed on the screen for longer, then participants' eyes would adjust so that both hemispheres could read the word.

The study found that the right hemisphere of the nappers' brains — which had a greater number of spindles during sleep, as recorded by the polysomnography device — fell more susceptible to "lure" words or false memories than the left. For example, the spindles might promote the word "sleep," telling the brain it remembers it from before, because it goes along with the general gist of words it had previously seen, such as "bed," "dream," "nap" or "snooze," Shaw said.

Sleep spindles have been linked to memory formation before, but previous "studies of [sleep] spindles have only examined true memories," not false memories, Shaw told Live Science. Indeed, sleep spindles are thought to play a very important role in consolidating short-term memory into long-term archives in the brain, and can also aid in cortical development. But this is the first study to find that sleep "spindles are accidentally creating [false] memories," Shaw said.

But don't get too mad at your brain — it's just trying to be efficient. "I think that the sleeping brain spends a lot of time and effort trying to identify the most important aspects of what was learned during the previous day," said Robert Stickgold, director of the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center, who was not part of the study.  

Stickgold noted that the new study doesn't provide enough evidence to undoubtedly say that the right side of the brain is dominant in creating false memories during sleep. "It didn't hit [statistical] significance, but [it] was close," he told Live Science. "But the correlation with sleep spindles is stronger, and I suspect it is real."

Because the study was small, Shaw said he hopes to increase the number of participants with subsequent experiments, in addition to expanding from naps to following the brain's mischief across a full night's sleep.

Originally published on Live Science.

Bad news for "night owls": Those who tend to stay up late and sleep in well past sunrise are at increased risk of early death, a new study from the United Kingdom suggests.

The research, which involved nearly half a million people, found that self-described "evening people" were 10 percent more likely to die over a 6.5-year period, compared with self-described morning people.

The findings add to a growing body of research that suggests that being a night owl could have negative effects on health. Many of these effects may be attributable to a misalignment between a person's internal clock, or circadian rhythm, and the socially imposed timing of work and other activities, the researchers said.

"'Night owls' trying to live in a 'morning lark' world may have health consequences for their bodies," study co-author Kristen Knutson, an associate professor of neurology at Northwestern University Feinberg School of Medicine, said in a statement.

The researchers said society needs to recognize that making night owls start work early may not be good for their health.

"This is a public health issue that can no longer be ignored," said study co-author Malcolm von Schantz, a professor of chronobiology at the University of Surrey in the United Kingdom. "We should discuss allowing evening types to start and finish work later, where practical." [5 Surprising Sleep Discoveries]

The researchers also called for more studies on whether night owls can adjust their circadian rhythms so that they become morning people, and whether such an alteration would lower those individuals' risk of health problems.

The study was published Wednesday (April 11) in the journal Chronobiology International.

Studying night owls

The study looked at medical data from about 433,000 people ages 38 to 73 living in the United Kingdom over a 6.5-year study period.

At the beginning of the study period, participants were asked whether they considered themselves to be morning people or evening people, or whether they felt they fell somewhere in between those two groups.

Evening people were at greater risk for certain health conditions, including diabetes, psychological disorders, gastrointestinal disorders, neurological disorders and respiratory conditions, the study found. But even after accounting for these conditions, the study still found that evening people had a slightly higher risk of dying during the study period, compared with morning people.

The study couldn't determine the reason for the link between being a night owl and the risk of early death.

There could be physiological consequences to having a sleep schedule that doesn't match your internal clock, the researchers said. For instance, some studies have found that people with such "circadian misalignment" have impaired glucose metabolism and impaired mood. Getting too little sleep is also known to have negative health effects, but the new study found little difference between the self-reported sleep of morning people and that of evening people, the researchers said.

Certain behaviors could play a role in the link found in this research. For example, some studies have shown that evening people are less likely to eat a healthy diet and more likely to use substances such as alcohol and illegal drugs, compared with morning people.

But regardless of the reason for the link, people may have some control over whether they are morning or evening people, the researchers said.

A person's "chronotype" appears to be about 50 percent genetic and 50 percent determined by the environment, Knutson said.

To become more of a morning person, the researchers recommend that people make sure they're exposed to light early in the morning, but not at nighttime, Knutson said. People should also try to keep a regular bedtime and not let it slip too much later over the weekends.

Original article on Live Science.

This Sunday marks the 100th anniversary of daylight saving time (DST), and what better way to celebrate than by losing an hour of sleep in the morning and gaining an hour of sunlight in the evening.

The time change happens at 2 a.m. local time on Sunday (March 11) — meaning that clocks everywhere will jump from 1:59 a.m. to 3 a.m. local time.

Spring daylight saving (not savings, as some people say) means that the sun will rise and set 1 hour later on March 11 than it did on March 10. In effect, this change gives people in the Northern Hemisphere more sunlight in the evening hours. And it turns out, the change may save the lives of koalas (keep reading). 

Daylight saving time was the brainchild of Benjamin Franklin, who devised the time change to conserve energy. But Franklin's idea wasn't implemented in the United States until about 100 years ago, on March 31, 1918, according to timeanddate.com.

But it's up for debate whether DST actually saves energy. The time change marginally decreased U.S. energy consumption, according to a study conducted by Stanton Hadley, a senior researcher at Oak Ridge National Laboratory, and his colleagues in 2007, Live Science previously reported. But DST increased residential energy usage in Indiana, a 1998 study found, and temporary changes in Australia for the 2000 Summer Olympics also didn't save any energy, according to a 2007 study.

Whether DST conserves energy or not, the main point is whether the extra hour of sunlight improves people's lives, Hadley said. "It's people wanting to take advantage of that light time in the evening," he noted.

But even that point may be bunk. People don't exercise more because of DST, a 2014 study in the Journal of Physical Activity & Health found. In the study, researchers compared data from residents who lived in Arizona, Colorado, New Mexico and Utah who participated in the 2003 to 2009 American Time Use Survey. Arizona does not observe DST, allowing the researchers to compare its results with those from the other states. (The Navajo Nation in northeastern Arizona, however, does observe DST.)

Although DST didn't significantly increase activity levels in the study, the researchers noted that the research was limited to the American Southwest, and that it's possible DST would make a difference in activity levels elsewhere.

There have been a multitude of other studies on DST. Research shows that losing an hour of sleep in the spring is associated with a spike in heart attacks, Live Science previously reported. The time change is also associated with more workplace injuries, increased cluster headaches and more cyberloafing, Live Science reported. People also tend to miss more medical appointments during shifts to and from DST, a 2017 study in the journal Chronobiology International found.

But there is this silver lining: DST may decrease the number of koalas killed by motorists in Australia, according to a 2016 study in the journal Biology Letters. That's because wild koalas (Phascolarctos cinereus) are nocturnal, and most vehicle accidents with wildlife happen at twilight or in darkness, during the evening commute, the researchers wrote. Shifting daylight hours with DST may reduce these wildlife deaths, according to a computer model created by the researchers. [Are Pets Affected By Daylight Saving Time?]

In Australia, where koalas live, Queensland and the Northern Territory (Western Australia) do not follow DST, according to the Australian government. In the United States, Hawaii is the only other state besides Arizona that does not observe DST.

Daylight saving time ends at 2 a.m. local time on Nov. 4.

Original article on Live Science.

• Why Does Daylight Saving Time Begin at 2 a.m.?
• 5 Weird Effects of Daylight Saving Time
• Daylight Saving Crime: When Clocks Fall Back, Assaults Spike

A new bedtime to-do list, courtesy of sleep researchers at Baylor University: 1. Write a to-do list before bed.

2. Go to sleep.

3. Sleep better than all the non-list-writing people you meet tomorrow.

It sounds simple, but there's evidence that it just might work. According to a small study published in the January issue of Journal of Experimental Psychology, participants who took 5 minutes to write out a to-do list before bed fell asleep more quickly than participants who wrote about tasks they had already completed. The key, according to researchers, is in mentally "offloading" responsibilities before bedtime, theoretically freeing the mind for sound sleeping. [How to Sleep Better]

"We live in a 24/7 culture in which our to-do lists seem to be constantly growing and causing us to worry about unfinished tasks at bedtime," lead author Michael Scullin, director of Baylor's Sleep Neuroscience and Cognition Laboratory, said in a statement. "Most people just cycle through their to-do lists in their heads, and so we wanted to explore whether the act of writing them down could counteract nighttime difficulties with falling asleep."

To test this hypothesis, researchers invited 57 men and women between ages 18 and 30 to spend one weeknight in a controlled sleep lab. The rules were simple: lights out at 10:30 p.m., and no technology, homework or other distractions allowed.

Five minutes before bedtime, each participant was instructed to complete a short writing exercise. Half of the participants wrote about anything they needed to remember to do in the upcoming days, while the other half wrote about tasks they had completed during the previous days. When the exercise was done, participants tucked in for bed. Researchers measured each participant's brain activity overnight using a technique called polysomnography, which records eye movement, muscle activity and other biological changes.

The researchers found that the participants who wrote to-do lists fell asleep an average of 9 minutes faster than those who wrote about already-accomplished tasks.

In fact, "the more specifically participants wrote their to-do list, the faster they subsequently fell asleep," the study authors wrote. "The opposite trend was observed when participants wrote about completed activities."

While 9 minutes may not seem like a lot of extra shut-eye, it's comparable to the improvement seen in clinical trials for some sleep medications, Scullin told Time magazine. A 2006 study similarly found that napping for just 10 minutes sufficiently improved participants' cognitive function and energy.

The authors acknowledged that the new study could be improved by a larger sample size and more data taking each participant's personality and propensity for anxiety into account. Still, the paper's findings are consistent with other published research on the therapeutic power of keeping a journal. Previous studies have observed that expressive writing — writing about emotions and stress for 20 minutes a day — was linked to boosted immune function in patients with illnesses such as asthma, arthritis and HIV/AIDS. Other studies have drawn a line between journaling in times of stress or emotional hardship and stress relief.

So, give writing before bed a try — and hope it's boring enough to put you to sleep.

Originally published on Live Science.

Is the trick to cutting cravings for sugary foods as simple as getting a good night's sleep? A new small study from the United Kingdom suggests that may be the case.

It's no surprise that tossing and turning all night can cause a person to feel tired, cranky and out of sorts the next day. But missing out on the recommended minimum of 7 hours of nightly shut-eye is also linked to various health conditions, such as obesity and cardiometabolic diseases, which include diabetes, heart disease and stroke, according to the study, published today (Jan. 9) in The American Journal of Clinical Nutrition.

Earlier research has shown that more than one-third of U.S. adults get 6 hours or less of sleep each night — less than the recommended 7 to 9 hours, according to the study. With that in mind, the researchers chose to examine whether a sleep consultation could help adults get more shut-eye and how doing so might affect their daily nutrient intake. [The Science of Hunger: How to Control It and Fight Cravings]

In the study, the researchers recruited 21 individuals to participate in a 45-minute sleep consultation designed to extend their sleep time by up to 1.5 hours per night. Another group of 21 participants were also recruited but did not receive intervention in their sleep patterns, therefore serving as the control group, according to the study.

All of the participants were asked to record their sleep and dietary patterns for seven days. During this time, the participants also wore motion sensors on their wrists that measured the exact amount of sleep they got each night, as well as the amount of time they spent in bed before they actually fell asleep.

The results showed that the participants who increased the amount of sleep they got each night reduced their added sugar intake by as much as 10 grams the next day compared with the amount of sugar they consumed at the beginning of the study. These participants also had a lower daily carbohydrate intake than the group that did not extend their sleep patterns, the study found.

"The fact that extending sleep led to a reduction in intake of [added] sugars, by which we mean the sugars that are added to foods by manufacturers or in cooking at home, as well as sugars in honey, syrups and fruit juice, suggests that a simple change in lifestyle may really help people to consume healthier diets," senior study author Wendy Hall, a senior lecturer in the Department of Diabetes and Nutritional Sciences at King's College London, said in the statement.

The group that got more sleep received a list with suggestions for how to help them get a better night's sleep — such as avoiding caffeine before bedtime, establishing a relaxing routine and not going to bed too full or hungry — as well as a recommended bedtime suited to their lifestyle.

"Sleep duration and quality is an area of increasing public health concern and has been linked as a risk factor for various conditions," lead researcher Haya Al Khatib, a professor from in the Department of Nutritional sciences at King's College London, said in the statement. "We have shown that sleep habits can be changed with relative ease in healthy adults using a personalized approach."

Overall, the results of the study showed that 86 percent of the participants who received sleep advice increased their total time spent in bed, and 50 percent of the participants extended their sleep duration by roughly 52 to 90 minutes each night, compared with the control group. What's more, three participants in the sleep-extension group achieved a weekly average within the recommended 7 to 9 hours, the researchers said.

However, the researchers noted one caveat to their findings: The data suggested that the extended amount of sleep may have been of lesser quality than the sleep of the participants in the control group. This is likely because any new routine requires an adjustment period, the researchers said.

"Our results also suggest that increasing time in bed for an hour or so longer may lead to healthier food choices," Al Khatib said in the statement. "This further strengthens the link between short sleep and poorer-quality diets that has already been observed by previous studies. We hope to investigate this finding further with longer-term studies examining nutrient intake and continued adherence to sleep-extension behaviors in more detail, especially in populations at risk of obesity or cardiovascular disease."

Originally published on Live Science.

Bad for You

Health risks can sometimes turn up in the most unexpected places. From getting licked by your dog to checking social media, researchers are uncovering hidden hazards that may be lurking in our daily lives that may possibly cause people harm or be unsafe.

Here are nine things you might do or experience while going about your day that could affect your health in surprising ways.

Going gluten-free

For some individuals, a gluten-free diet is not a choice, but a necessity: People with celiac disease, a rare condition in which eating gluten triggers an immune response that damages the small intestine, must avoid gluten. People with a diagnosed wheat allergy should cut back on gluten by avoiding wheat.

But as gluten-free diets have gained popularity, many people believe that avoiding gluten is healthier for them. Some say that they feel better and lose weight after cutting back on gluten or cutting out foods containing the protein, such as most breads, cereals, pastas, desserts and many processed foods.

However, nutrition experts say these health benefits could result from the foods people may be eating in place of those with gluten, such as more fruits and vegetables, and fewer sweets and junk food, as opposed to the benefits stemming directly from avoiding gluten. Nutrition experts also say that gluten-free products tend to cost more, and some gluten-free packaged foods may be higher in fats and sugar than products with gluten.

What's more, cutting out gluten could be risky for some people. For example, eliminating this protein from children's diets, when they don't have celiac disease or a wheat allergy, could lead to certain nutritional deficiencies, experts say.

Getting too much sleep

Many Americans get too little sleep. But sleeping too much can also have its pitfalls.

In a study that was presented at the American Heart Association's medical meeting this year, researchers found that getting too much sleep was linked to poorer heart health in older women.

Researchers found that older women who slept more than 9 hours a night had an estimated 13 percent risk of developing heart disease in the next 10 years, compared with an estimated risk of 12 percent in women who slept for 7.5 to 8 hours a night.

Other research has also shown that too much sleep can affect the risk of heart disease. But previous studies have asked people to remember how much they typically slept, whereas the new study used a more objective measurement of actual sleep, which may provide a more accurate estimate.

The researchers noted that the study had limitations. For example, it did not factor in whether these women took sleeping pills or had a sleep disorder, which could have impacted the results. The findings have not yet been published in a peer-reviewed journal.

Taking vitamins

People may take a multivitamin to cover nutritional gaps in their diet or to stay healthy. But researchers have shown that these popular supplements may not protect against chronic disease, and could be a waste of money.

Three studies done in 2013 found no evidence that taking a daily multivitamin prevents or slows the risk of developing chronic diseases, such as cancer and heart disease, or delays the progression of cognitive decline.

Results from earlier studies have also shown no benefits from taking antioxidants or B vitamins and even suggested some possible harm. Despite these findings, supplement sales in the U.S. remain strong.

In 2017, the U.S. Food and Drug Administration outlined another potential harm from taking supplements. They issued a warning to consumers about the risks of high doses of biotin, a B-complex vitamin.

High levels of biotin in the blood can skew the results of some lab tests, including tests that measure hormone levels and tests that detect heart attacks, the FDA says. These faulty test results have been linked to one death, the FDA says.

It's not clear how much biotin may interfere with lab results, but researchers are investigating the amount. The Institute of Medicine recommends 30 micrograms of biotin daily, whereas some supplements can contain more than 650 times the recommended amount.

Sitting all day

A desk job keeps your behind plastered to a seat for hours, which studies have shown can be hazardous to your health.

Long periods of sitting have already been linked with diabetes and heart disease. And a 2015 study identified yet another risk: Women who sat for more than 6 hours a day had a higher risk of developing breast cancer, ovarian cancer and multiple myeloma (a form of blood cancer), compared to women who sat less than 3 hours a day.

Similar results were not seen in men, except for those who were obese. Heavier men who spent more time sitting also had an increased cancer risk.

A second study investigated whether sitting was associated with other unhealthy behaviors. This analysis showed that people who spend most of the day sitting and sleeping too much may be as likely to die early as people who smoke or drink too much.

In a third study, researchers found that exercising may be one way to reverse some of sitting's negative effects. Working out for at least an hour a day could reduce or eliminate some health risks from long-term sitting, the researchers said.

Using a smartphone

Smartphones seem indispensable, but the more people use them, the more health concerns pop up.

Take sleep problems, for instance. Adults who spent more time on their smartphones before bedtime took longer to fall asleep and didn't sleep as well or as much, compared with people who used their phones less before hitting the sack, a 2016 study revealed.

One reason could be that exposure to the screen's blue light may suppress the brain's production of the hormone melatonin, making it harder to nod off.

Smartphones may affect the brain in other ways: A small study found chemical imbalances in the brains of teens who were addicted to using their smartphones. Brain scans showed the teens produced too much of the neurotransmitter gamma-aminobutyric acid (GABA), in an area of the brain that controls emotions.

Frequent phone use may not only throw off brain chemistry, it may also cause short-term vision loss. A case report found that checking your phone at night while lying in bed in a dark room could lead to a loss of sight in one eye for several minutes.

Logging onto social media

Although social media is designed to help people feel more connected, all that posting, sharing and liking could make some young people feel more alone, a 2017 study suggests.

Young adults who spent more than 2 hours a day on popular social media sites, including Facebook, Instagram and Twitter, were about twice as likely to feel socially isolated as their peers who spent less than 30 minutes daily on these sites.

Social isolation means feeling like you don't belong and lack the skills to engage with others and form fulfilling relationships.

The researchers say it's not clear whether the reason young people turn to social media for connection is because they already feel isolated, or whether they feel more isolated after increasing their media use.

Some possible explanations for the findings are that social media could be limiting face-to-face interactions, and may be giving young people a false impression that other people their age are leading happier lives than they are, the researchers said.

Drinking diet soda

Two studies suggest that drinking diet soda may not be so good for your brain.

In one study, researchers found that middle-aged and older adults who consumed diet soda every day were three times more likely to have a stroke or develop dementia over a 10-year period, compared with those who did not drink any diet soda.

Although the exact reasons are unclear, previous studies have linked the consumption of diet soda with obesity and diabetes. Both of these health problems are tied to poor blood circulation, which can affect a person's risk for stroke and dementia.

In another study, the same researchers found that people who drank at least one diet soda a day had smaller brain volumes than those who never consumed diet beverages.

But switching from diet soda to sweetened beverages may not lead to better brain health: The findings also showed that people who drank more than two sugary beverages a day, which could include soda or juice, had smaller brain volumes and poorer memories than people who had no sweetened drinks.

Receiving doggie kisses

Doggie kisses are usually welcomed signs of affection, but sometimes this tongue bath to your nose and face can have unforeseen consequences. In one woman's case, the sloppy smooches from her pooch caused her to develop a severe bacterial infection.

The 70-year-old woman was taken to the hospital after collapsing in a chair, according to a 2016 report of her case. But four days later, she also came down with a high fever, headache, chills and diarrhea, and lab tests showed her kidneys were failing.

Blood tests eventually revealed that the woman was infected with Capnocytophaga canimorsus, a bacteria found in the mouths of dogs and cats. Scratches and bites from pets can also transmit the infection.

Although the woman had no bites or scratches, she told doctors that her Italian greyhound licked her. Her doctors said that pet owners, especially older adults with weak immune systems, might pick up this bacterial infection from their dogs or cats during these slobbery displays of affection.

Owning other pets

A pet's unconditional love is hard to resist, but these close encounters with certain domestic animals can sometimes make people sick.

In 2015, for example, there were at least four Salmonella outbreaks in the U.S. that were linked to close contact with "backyard chickens," according to the Centers for Disease Control and Prevention (CDC).

Many people came down with the bacterial infection, which can cause diarrhea, fever and stomachaches, by allowing backyard chickens into their homes as pets, or while kissing and handling the animals.

And Salmonella isn't the only issue associated with backyard chickens. A 2016 study suggested that backyard chickens raised in cities may be exposed to a broader range of parasites that can infest the bird's skin than commercially raised chickens.

The chickens can pick up the parasites, including fleas, mites and lice, while roaming the yard, but the study authors found that the birds' owners were unaware of these creepy-crawlies cohabitating with their pets.

Small pet turtles have also been tied to Salmonella outbreaks, the CDC says. To prevent the slow-moving reptiles from shedding Salmonella germs, the agency advises against bringing small turtles into homes and schools.

Worried you might say something you regret when talking in your sleep? Your concerns may be justified: According to a recent study from France, your midnight mumblings may be more negative and insulting than what you say while awake.

In the study, researchers found that sleep talkers said the word "no" four times more often in their sleep than when awake. And the F-word popped up during sleep talking at a rate of more than 800 times than what was spoken while awake.

To study sleep talking, the researchers recorded nearly 900 nighttime utterances from about 230 adults over the course of one or two consecutive nights in a sleep lab. Because sleep talking is a relatively rare event, the majority of people in the study had certain types of sleep disorders, or parasomnias, which are unusual behaviors that happen during sleep, the researchers noted. [Top 11 Spooky Sleep Disorders]

Once recorded, the nocturnal episodes were analyzed for such factors as wordiness, silences, tone, politeness and abusive language. These results were compared with the largest bank of French spoken language to see how sleep speech matched up to everyday spoken French in form and content.

The researchers found that the majority (59 percent) of the nighttime utterances were unintelligible or nonverbal, including mumbling, whispering or laughing.

But among the utterances that were intelligible, a surprising amount of what was said was offensive or aggressive: 24 percent of the utterances contained negative content, 22 percent had "nasty" language and almost 10 percent contained the word "no" in some form. (In comparison, the word "no" accounted for 2.5 percent of awake language.)

The F-word also made a frequent appearance and was one of the most common words spoken during sleep talking: It showed up 2.5 percent of the time, compared with just 0.003 percent of spoken words while awake. In total, 10 percent of all clauses spoken during sleep contained profanity.  

Why so negative? The findings may reflect what's called the "Threat Simulation Theory," which is one explanation for the function of dreams, according to the study. The theory posits that dreams are simulations that help "train" people for threats that could happen while awake, providing an evolutionary purpose for dreaming.

Though the study participants were French, the findings don't necessarily mean that French people are ruder than other nationalities, said lead study author Dr. Isabelle Arnulf, a neurologist at the Pitié-Salpêtrière Hospital in Paris. In fact, the study mirrors anecdotal findings of sleep talk content from abroad, Arnulf told Live Science.

And although the content spoken during sleep may have been more offensive and nasty, the speech was otherwise similar to that used when awake, Arnulf said. Sleep talking tended to remain grammatically correct and followed patterns of everyday speech regarding pauses and the number of words used in a given statement.

Dr. Carl Bazil, director of the Division of Sleep and Epilepsy at Columbia University in New York City, who was not involved in the study, told Live Science that the findings show that sleep speech is much more "complex than expected" and supports the idea that there is "higher brain function" during all stages of sleep.

Indeed, the fact the phrases spoken during sleep were largely grammatically correct suggests that the same neural system is functioning as when people are awake, according to the study. At the same time, the large amount of mumbling shows that there is still some motor inhibition at play; in other words, the brain is still blocking muscle movement.

Ultimately, the sleep speech in the study suggests a complex level of brain functioning that could help give scientists more insight into the purpose and process of dreams, even if, at the same time, it shows a less-than-flattering side of ourselves, the researchers wrote.

The study was published last November in the journal Sleep.

Originally published on Live Science.

If you've ever woken up in the middle of the night feeling as though you're being crushed by a demonic being, you may have just experienced what's called the incubus phenomenon: an "attack" by a male demon. (Its female counterpart, the succubus, usually attacks men.)

The phenomenon is, in many ways, the quintessential nightmare. For centuries, the incubus demon has been said to haunt sleepers, inspiring tales in traditional folklore as well as works of art.

Now, a new meta-analysis from the Netherlands suggests that this frightening phenomenon may be more common than previously thought — and that it should be taken more seriously by psychiatrists and psychologists who hear such accounts from their patients. [Top 11 Spooky Sleep Disorders]

The so-called attack usually occurs during an episode of sleep paralysis, a condition that's even more common than the incubus phenomenon, according to the meta-analysis.

Sleep paralysis is a result of the dissociation of sleep phases, said senior author Dr. Jan Dirk Blom,a professor of clinical psychopathology at the University of Leiden in the Netherlands.The condition happens when a person is falling asleep or waking up. During sleep paralysis, two aspects of REM sleep, or rapid eye movement sleep, occur when a person is conscious.

During REM sleep, which is the period when a person typically dreams, the body's muscles are relaxed to the level of paralysis, presumably to prevent the sleeper from acting out his or her dreams, Blom said. But when sleep paralysis takes place, the person's mind wakes up — however, the person is still dreaming, and the body is still paralyzed.

"Lying in bed in such a state of paralysis, the brain's threat-activated vigilance system kicks in and helps to create a compound hallucination of a creature sitting on the chest," Blom told Live Science.

What the afflicted person sees is a combination of their actual surroundings and a nightmare, which is projected onto the real world. The experience feels exceptionally real, Blom said.

Tracking demons

In the meta-analysis, which was published in November in the journal Frontiers in Psychiatry, the researchers looked at 13 studies of the incubus phenomenon that included nearly 1,800 people. The different studies came from various countries, including Canada, the United States, China, Japan, Italy and Mexico.

The researchers found that over 1 in 10 people, or 11 percent of the general population, will experience the incubus phenomenon in their lifetimes, Blom said. "That means that there is an 11 percent chance for any given individual to experience this [the incubus phenomenon] at least once during their lives," he added.

But in certain groups, the odds of "encountering" an incubus are higher. Among people with psychiatric disorders, as well as among refugees and — somewhat surprisingly — students, the odds of experiencing the incubus phenomenon are as high as 41 percent, Blom said.

The analysis also found that people sleeping on their backs are more likely to experience the phenomenon. Alcohol consumption and irregular sleeping patterns also make an incubus visit more probable, Blom said.

Though the frightening experience gets frequently dismissed as "just a bad dream," Blom noted that the incubus phenomenon can lead to additional problems, including anxiety, difficulty sleeping due to fear and even delusional disorder, a mental illness akin to schizophrenia.

In the paper, the researchers speculated about a possible link between the incubus phenomenon and sudden unexpected death syndrome, a situation in which a healthy person inexplicably dies in his or her sleep.

"People who have experienced the incubus phenomenon often report a level of anxiety that is 'off the scale,'" Blom said. "Many of them have the feeling that they will actually die during an attack. Whether that ever happens is unknown, even though for a person experiencing it, it is not hard to imagine this [happening]."

The analysis also found that the form of the incubus figure and how people react to it can vary based on the person's cultural background.

For example, "patients with Muslim background often tell me that they see the incubus phenomenon as a proof that they are being haunted by a jinn, an invisible spirit created by Allah out of smokeless fire," Blom said.

Sometimes, however, the incubus may take on a much more friendly and entertaining form.

"I recently spoke to a healthy 15-year-old girl who had experienced the incubus phenomenon," Blom said.  "She found four miniature penguins dining at a table on her chest, and had been thrilled and amused rather than scared."

Originally published on Live Science.

Ken A. Paller is a professor of psychology and director of the Cognitive Neuroscience Program at Northwestern University in Evanston, Illinois. Paller has contributed this article to Live Science's Expert Voices: Op-Ed & Insights.

Sleep will consume one-third of your life. You can't avoid it, nor should you. Sound slumber is energizing and uplifting. But there's more to it. Sleep is also essential for effective learning.

The essence of who you are — your memories and habits — may all depend on what your brain does while you sleep. Electrical recordings show that the brain is far from idle when you snooze. Neuroscientists have conjured up many ideas to try to explain this mysterious neural activity.

Here's one such idea: Picture a house-elf from Harry Potter's world spending the whole night busily organizing and rearranging memories so they’ll be in good working order the next morning. [5 Surprising Sleep Discoveries]

Yes, that’s implausible, but consider that during a typical day, countless memories are stored in your brain. After a few days, most are forgotten, as if they somehow disappeared (one might say, “disapparated”).

Your best bet to counteract some of this massive memory loss is to practice what you've learned, the same way actors rehearse lines of a play. Neuroscience research is helping us understand how new information can be gradually integrated into your brain's memory networks this way. When you want to memorize something, you should bring it to mind and rehearse it. Repeatedly. The effort you expend working to remember something pays off because corresponding brain networks change, enhancing long-term storage.

But that's not the only way to strengthen memory storage.

As I described in a new paper in the journal Current Directions in Psychological Science, recent investigations from many labs around the world show that this "rehearsal" also happens while we sleep — a time when we seemingly lack both the intention to rehearse and any awareness of doing so.

Listen for the tone

A key methodological breakthrough fueling these new insights makes use of odors or sounds. For example, if a special tone is played while learning a particular fact, the tone and the fact can be linked. Later, during sleep, that same tone can provoke the neural plasticity (changes in connections between neurons) central to storing that information within the brain’s circuitry.

Although the orthodox view used to be that hearing is mostly inoperative during sleep, in 2009 my students and I discovered that subtle sounds played during deep sleep promoted rehearsal without awakening our volunteers. The sounds worked as "memory reminders" because they could readily reactivate recently acquired information in the brain.

In these experiments, now repeated many times, we ask people to learn locations of various objects while listening to specific sounds, and then they take a nap in the lab. After they wake up, they recall locations more accurately for objects linked with sounds that we surreptitiously played during sleep. In this way, sound presentations during sleep have allowed neuroscientists to hack into recent memories. 

Memory "hacking"

These findings raise the possibility that people could select specific memories to reactivate while they sleep in their own homes. Why do this? Ordinarily, natural reactivation of memories in sleep may not be optimal, and we unknowingly rehearse things we'd prefer to forget. For example, is your sleep filled with annoying advertising you encountered during the day? Perhaps you could shift the bias to emphasize what you really want to remember instead. [10 Ways to Keep Your Mind Sharp]

The possibilities for selecting memories to consolidate during sleep are vast, including the strengthening of specific skills. Researchers in 2015 conducted a study showing they could boost learning of Dutch vocabulary using verbal cues during sleep. Similarly, work from my lab provided evidence that sleep cues could improve learning with respect to the abstraction of grammatical rules, an important part of becoming fluent in a new language. We also strengthened musical skills during sleep in a study in which volunteers first learned to perform two melodies, and then woke up better at the one melody that had been quietly presented to them while they slept.

Some skills and habits are acquired or expressed without us knowing it. One such bad habit is teeth grinding during sleep. Reactivating memories during sleep could perhaps help people to unlearn such habits. The idea would be to first train people to release jaw tension when hearing a special sound during the day. That same sound would then cue them to relax the jaw during sleep. We think that novel experimental therapies like this hold promise, given our results with habit learning of a different sort; we were able to reduce implicit social bias using sounds initially associated with anti-bias training and subsequently played during sleep.

Valuable benefits might arise even when strategic reactivation of memories during sleep produces only small changes. Consider recovery after a stroke. Rehab sessions aim to revitalize brain networks essential for movement or language. Recovery depends on how well learning progresses. With only a few hours of therapy a week, it can take a while for this learning to take hold. Sleep-assisted therapy, using specific sounds associated with desired actions and also played nightly, might quicken recovery.

Ethical considerations

New means for tinkering with memory storage demand a deep dive into ethics. Aldous Huxley imagined how bad things could go in his "Brave New World": The state controlled citizens through "hypnopaedia," or sleep teaching. People assumed their assigned roles in society, high or low, because they were bred that way, compelled to be avid consumers, with little choice in the matter. While we should proceed cautiously with new technology, current methods require first training people when they are awake, such that what they are learning isn't hidden and they have the option to reject it.

Neuroscience has opened the door to new possibilities for guiding the sleeping brain to work better. In a sense, elves really do clean your brain while you sleep. With further scientific efforts in these various new directions, a refined understanding of the sleeping brain could bring wide-ranging benefits, and give us more reasons to treasure — rather than resent — our need for sleep.

Originally published on Live Science.

After a stressful day, you may hope to find some solace in sleep. But a new study from the United Kingdom suggests that stressful experiences from your day can make their way into your dreams.

The findings, published Nov. 30 in the journal Motivation and Emotion, suggest that, even in your sleep, you can't escape your nagging boss and other daily pressures. And if you feel lonely and isolated in your daily life, those feelings and emotions can also infiltrate your dreams.

"Our results show that there really is something about the mind holding onto really powerful social experiences," said lead study author Netta Weinstein, a senior lecturer in social and environmental psychology at Cardiff University, in the U.K. "If our lives are very challenging, that seems to repeatedly show and come back to us in the form of dreams." [7 Mind-Bending Facts About Dreams]

In the study, the researchers looked for links between people's dream experiences and whether three particular psychological needs were fulfilled or left people feeling frustrated: the need to feel competent, the need to feel autonomous, and the need to feel related to other people.

The need to feel competent included feeling competent at work or in any area that people find important, Weinstein said. The need to feel autonomous included whether people didn't feel controlled or pressured to do things they didn't want to do, and the need to feel related to others included feeling connected to close people in their lives.

The researchers conducted two separate experiments. In the first experiment, they asked a group of 200 students to recall a frequently recurring dream. Then, the researchers compared the dreams to what was going on in the students' lives and whether their psychological needs were met. In the second experiment, the researchers asked a group of 110 students to record their dreams for three consecutive nights and report any significant events from each day before.

The researchers found that the emotional charge of the dreams frequently corresponded to frustrating events related to the three needs that they had experienced during the day.

"When people had these really frustrating, upsetting experiences in their everyday [lives], they had dreams where they felt stressed, sad or frustrated," Weinstein told Live Science.

"The link between the experiences and the content of the dreams was less robust," Weinstein noted. "But we found some evidence that [that dreams about] falling, being attacked by someone, being locked up or trying repeatedly to do something and failing at it" could be linked to a frustrating experience during the day.

Weinstein said that, in the study, the researchers didn't try to differentiate among the three types of unfulfilled psychological needs because the number of dreams that were available to analyze was rather small. Together, both experiments provided about 400 dreams, which was not enough for a more advanced analysis of the content of the dreams, she said.

"You would need a lot of dreams to be able to look at specific types of content and see whether these relate to isolation or incompetence, for example," Weinstein said. "Our [study] was kind of a broad-stroke approach to examining how the stuff that we are experiencing in our waking lives makes its way into the dreams."

The findings suggest that negative experiences from our waking life could negatively affect our ability to get a good night's sleep, Weinstein said. Moreover, the researchers found that people with less fulfilling, more stressful lives reported more frequent recurring stressful dreams.

Still, more research into the meaning of dreams is needed, Weinstein said. Sigmund Freud pioneered the study of dreams in the late 19th century, proposing that dreams show the contents of the mind that have been suppressed into the subconscious. But more than a century later, scientists are still not entirely sure of the function of dreams, Weinstein said.

Originally published on Live Science.

ANAHEIM, Calif. — Getting too much sleep may increase the risk for heart disease in older women, early research suggests.

In a new study, researchers analyzed information from more than 3,000 older women in the United States who wore a fitness tracker-like device called an ActiGraphic, which measures activity as well as sleep, for one week. Participants were 78 years old on average, and represented a racially and ethnically diverse group.

The researchers also calculated each participant's "Reynolds Risk Score," a score that estimates a person's risk of developing cardiovascular disease, or experiencing a complication like a heart attack or stroke, over 10 years.

The results showed that, for women who slept more than 9 hours a night, their estimated odds of developing cardiovascular disease in the next 10 years was about 13 percent, compared with 12 percent for those who slept 7.5 to 8 hours a night. [5 Surprising Sleep Discoveries]

Although this is only a small increase in risk, the results were statistically meaningful, and held even after the researchers took into account factors that could also play a role, such as age, body mass index (BMI), smoking habits, alcohol use and self-rated health.

Several earlier studies have found a relationship between getting too little or too much sleep and a person's risk for cardiovascular disease. However, most of these earlier studies relied on self-reported measures of sleep, meaning the researchers asked participants to report how much sleep they typically got at night, said study lead author Kelsie Full, a doctoral candidate in the Department of Family Medicine and Public Health at the University of California San Diego, who presented the findings here on Monday (Nov. 13) at the American Heart Association's Scientific Sessions.

The new study adds to the scientific literature by using objectively measured sleep, which may be more accurate than people's self-reports, Full told Live Science.

However, it's important to note that the study found only an association, and cannot prove a "cause and effect" relationship between getting too much sleep and an increased risk of cardiovascular disease. Other factors not included in the study, such as participants' use of sleep medication, or whether or not they had a sleep disorder, could affect the results.

But the findings are interesting because guidelines for healthy sleep typically emphasize the need to get an adequate amount of sleep. "Potentially, too much sleep is also something to be concerned with," and future studies should explore this relationship more, Full said.

It's recommended that adults ages 65 years and older get 7 to 8 hours of sleep a night, according to the National Sleep Foundation.

Full said the next step for her research will be to look at whether getting too little or too much sleep is linked with actual cardiovascular events, including heart attacks and strokes, rather than looking at a person's predicted risk, as she did in this study.

The findings have not yet been published in a peer-reviewed journal.

Original article on Live Science.

Daylight saving time ends on Sunday, Nov. 5, which means most people in the U.S. will turn their clocks back an hour — but a new study finds that this extra bit of shut-eye may not be as beneficial as some may think. 

In the study, researchers found that assault rates are higher on the Monday following the end of daylight saving time, compared with the next Monday.

And in the spring, the researchers observed the opposite: a decrease in assault rates on the Monday following the start of daylight saving time, compared with the next Monday, according to the study, which was published online in September in the Journal of Experimental Criminology.

Long-term sleep deprivation is commonly linked to higher rates of antagonistic or criminal behavior. However, researchers in the new study found that in the short term, losing an hour of sleep can have the opposite effect: After the start of daylight saving time in the spring (when we turn the clock ahead 1 hour), assault rates dropped by about 3 percent, according to the study. 

In contrast, as people "fell back" and gained 1 hour of sleep, the average assault rate increased; it was 3 percent higher on the Monday immediately following the end of daylight saving time, compared with the Monday a week later, the researchers found.

"Sleep problems have previously been associated with increased antisocial and criminal behavior, so we were surprised to find that increased sleep [rather than decreased sleep] was associated with increased offending," study co-author Adrian Raine, a professor of criminology, psychiatry and psychology at the University of Pennsylvania, said in a statement. "This discrepancy is likely due to the fact that 40 to 60 minutes of lost sleep in one night is just not the same as months, or even years, of poor sleep."

In the study, the researchers analyzed crime data from New York, Chicago, Los Angeles and Philadelphia from 2001 through 2014. They compared assault rates on the Monday immediately following daylight saving time to the Monday a week later. Then, they repeated this when clocks returned to standard time in the fall.

"In the spring, the day after we move into daylight saving time, there are more car accidents, greater stock market losses, more workplace injury, reduced test scores and higher suicide rates," senior study author Greg Ridgeway, an associate professor of criminology and statistics also at the University of Pennsylvania, said in the statement.

But a loss of sleep didn't have the same effect on crime rates. This may be because people are just too groggy to act on their aggression after losing that hour of sleep in the spring, the researchers suggested.

"You think, 'If I don't get a lot of sleep, I'm going to be cranky and angry.' You assume that's the way you would react," lead study author Rebecca Umbach, a doctoral student in criminology at the same institution, added. "Your intention is to act more aggressively, but your behavior does not reflect that, because you're tired. You're too lethargic and sleepy to act."

The researchers were unable to explain, however, the increased number of assaults following the end of daylight saving time, when people generally get more sleep. More research is needed to tease out this link.

Original article published on Live Science.

In the 2010 film "Inception," Cobb (Leonardo DiCaprio) describes his wife Mal's trick for discerning reality from the fantastic dreamscape in which most of the film takes place: He uses what he calls a totem, a spinning top that will never fall over while he's dreaming. But a totem, known to psychologists who study lucid dreams as a reality check, is actually one of the less-effective ways to tell whether you're asleep, a new study from Australia finds.

If you've ever realized you were dreaming while you were still asleep, you've had what's called a lucid dream. Though these dreams can happen by chance, there are communities of people who try different techniques to bring them about.

So, in the new study, researchers decided to take these techniques to task, testing out which methods worked best for inducing lucid dreams. If people know how to effectively induce a lucid dream, then researchers will be able to learn more about the dreams themselves down the road, the researchers said. [7 Mind-Bending Facts about Dreams]

"Ultimately, I want to develop techniques that are effective enough to permit serious exploration of the many potential benefits and applications of lucid dreaming," said lead study author Denholm Aspy, a visiting research fellow in psychology at the University of Adelaide in Australia.

In the study, which was published in the journal Dreaming in September, the researchers asked nearly 170 participants to try out three techniques that have been said to increase the likelihood of lucid dreaming.

One of the techniques tested in the study was the use of reality checks. These included closing one's lips and trying to inhale; in a dream, you might get the sensation of breathing in because your body perceives the change in facial muscles. Another reality check was reading printed text, which, in dreams, often changes from one reading to another, the researchers said.

The two other techniques were called "wake back to bed" and "mnemonic induction of lucid dreams" (MILD). Both approaches involve waking up for a few minutes after 5 hours of sleep before going back to bed, but the MILD technique also involves repeating the phrase, "Next time I'm dreaming, I will remember that I'm dreaming," before falling back to sleep.

At the beginning of the study, the participants recorded the number of lucid dreams they had over the course of a week. Then, for the second week, the participants were randomly assigned to one of the three groups: reality check, reality check plus wake back to bed, and reality check plus wake back to bed plus MILD. Again, the participants recorded the number of lucid dreams they had.

The researchers found that when all three techniques were used (the third group), people were able to recall more lucid dreams after two weeks than those who had done only one or two of the techniques. The group that tried all three techniques reported having a lucid dream 17 percent of the time. And falling asleep within 5 minutes of practicing the MILD approach bumped the success rate up to around 46 percent compared with those who tried this technique but took longer to fall asleep. Reality checks alone, however, were not linked with an increased rate of lucid dreams.

"Inception" fans shouldn't necessarily throw out their collectible tops. Aspy told Live Science that other studies that ran as long as three weeks found more success with reality checks. Perhaps this technique wasn't as effective in the new study because the participants didn't have enough time to build up the habit to the point that they would think to try it while dreaming, Aspy said.

Dr. Rafael Pelayo, a sleep medicine specialist at Stanford University who was not involved in the research, said that "it's nice that there's actual research" lucid dreaming now. [Spooky! Top 10 Unexplained Phenomena]

Pelayo noted that lucid dreaming didn't seem to be linked to a reduction in sleep quality, but that this might be an area for future research. Some brain-scan studies have suggested that when a person is experiencing a lucid dream, the brain is in a sort of hybrid sleep-awake state rather than fully asleep, he said.

In the future, the researchers hope to study practical uses for lucid dreaming, though these are still largely speculative, Aspy said. Some research, for example, suggests that lucid dreaming could be used to practice hobbies and crafts, and then see an improvement in waking life.

"We're touching on some things that are hard to know," Pelayo told Live Science. He thinks it's unlikely, for example, that athletes could use lucid dreaming to effectively practice their sport, but he's also interested in seeing what future research reveals down the road. It's possible that one day, people with post-traumatic stress disorder could use lucid dreaming to help avoid nightmares, he said. But to study these applications, "the first step is teaching people to reliably do lucid dreaming, and that's what this paper offered," he added.

"Lucid dreaming has been around for a long time," Pelayo said. "There are online communities around it, people buying supplements online, so adding some science can only be helpful. I think it’s long overdue."

Originally published on Live Science.

The quality of your sleep could play a role in how your brain responds to fear, which, in turn, could determine how likely you are to develop post-traumatic stress disorder (PTSD), a small, new study suggests.

People in the study who got more "rapid eye movement" (REM) sleep had less activity in the areas of the brain linked to fear in the face of a frightening event, compared with those who got less REM sleep, according to the study, published today (Oct. 23) in the Journal of Neuroscience.

The findings suggest that REM sleep may help keep fear levels low by altering how certain areas of the brain communicate with one another, the researchers wrote. This could mean that scientists could one day use a person's REM-sleep measurements, or how much time the person spends in REM sleep, to predict how resilient that person is to trauma or, conversely, how likely the person is to develop PTSD following a traumatic event, they wrote. [Get Better Sleep in 2017]

The new study "is a very good first step in understanding the mechanism of resilience," said Anne Germain, an associate professor of psychiatry and psychology at the University of Pittsburgh School of Medicine, who was not involved in the research.

In the study, 17 healthy college students had their sleep monitored at home for between five and 13 days, to establish their baseline sleep patterns, including their levels of light, deep and REM sleep. The students were paid to participate in the study.

Then, the students underwent a "fear conditioning" test: They were shown a series of red, yellow or blue lights that they had been conditioned to associate with mild electrical shocks. In other words, if a mild shock always followed a blue light, the student would anticipate, and likely fear, the shock when shown the blue light. During the test, the researchers monitored brain activity in the participants' amygdala, hippocampus and ventromedial prefrontal cortex — areas of the brain associated with the fear response. (The colored-lights test is a widely accepted model for studying PTSD, Germain told Live Science.)

Finally, the researchers sent the participants back to bed one more time. They monitored the subjects' sleep for one full night in the lab and then had them repeat the fear-conditioning test. The findings showed a noticeable correlation between the amount of REM sleep a person got and the magnitude of his or her fear reaction to the colored lights: The more REM sleep a person got during the baseline period, the less extreme his or her fear response was.

The finding suggests that REM sleep may play a key role in helping the brain prepare itself for, and withstand the effects of, emotional trauma, the researchers said.

There's growing evidence that the quality of a person's sleep has some link to the occurrence or severity of a number of psychological conditions, ranging from PTSD to depression. However, this study is the first significant one to explore whether a person's pattern of sleep can be used to predict whether he or she might be vulnerable to PTSD, the study authors said. The results of the new study could mean that scientists might someday be able to tell whether someone is suitable for a high-stress profession based on his or her normal sleep patterns, the researchers said.

Still, more research is needed to fully understand how REM sleep and PTSD are linked. It's not clear, for example, if getting more REM sleep could help keep PTSD at bay. [5 Surprising Sleep Discoveries]

Another question is whether a person can get too much REM sleep: Is there a "sweet spot" past whichtoo muchREM sleep might raise a person's risk of PTSD? REM sleep is when dreaming takes place, and there's a known connection between PTSD and intense dreams or nightmares, Germain said.

Germain noted that the researchers looked only at the average amount of REM sleep the participants got over the course of the study, and how this compared to the fear response. So it would be interesting to see if the response would change based on the amount of REM sleep each person got each night.

Still, the results are promising both for the field and people with PTSD, she said.

"This is a really good example of the importance of sleep in maintaining healthy emotional health," Germain said. "Sleep is still considered to be that phase when you do nothing at night. We all tend to cut back on our sleep to do everything that's so important during the day. But by doing that, we're really cutting ourselves short and putting ourselves at a disadvantage when facing important life events."

Originally published on Live Science.

They don't have brains, or even anything more than a rudimentary nervous system, but jellyfish apparently do have bedtimes.

New research finds that jellyfish enter a sleep-like state. If the study, published today (Sept. 21) in the journal Current Biology, is confirmed by future studies, jellyfish are the first-ever animals with no central nervous system to have been observed sleeping. That finding could bolster the theory that sleep is an emergent property of neurons — in other words, sleep might be something that nerve cells connected in a network just do, even without complex organization.  

"The real novelty of what we've shown is that this animal that is almost as far away, evolutionarily, from humans and higher animals as you can go, also seems to have this conserved behavioral state" of sleep, said study co-author Claire Bedbrook, a doctoral student in bioengineering at the California Institute of Technology. [See Adorable Photos of Animals Sleeping]

The origins of sleep

Sleep is crucial to survival, but no one knows exactly what it does or why it first evolved. A 1995 study in the journal Behavioural Brain Research found that when deprived of sleep completely, rats died within three weeks. Animals as simple as the worm Caenorhabditis elegans, which has just 302 neurons and an extremely simple central nervous system, have been found to exhibit patterns of activity and rest that look an awful lot like sleep.

Ravi Nath, a Caltech graduate student and a co-author of the new study, typically studies this sleep-like state in C. elegans. He and his lab adviser, Paul Sternberg, wondered if they could find evidence of sleep in even simpler animals. Jellyfish came to mind, Nath told Live Science.

Another Caltech graduate student, Michael Abrams, happened to be cultivating jellyfish in the lab of biologist Lea Goentoro at the same time for an entirely unrelated project. He noticed that one genus, Cassiopea, or the upside-down jellyfish, seemed to become less active at night. Cassiopea spends the vast majority of its time sitting upside down on the ocean or tank floor, pulsing its bell about once a second, Abrams told Live Science. This sedentary behavior makes the upside-down jellyfish an easy animal to track behaviorally.

Snoozing jellies

Abrams and Nath joined forces with Bedbrook to investigate just what the jellies were doing. They knew that to show that the jellyfish were sleeping, they'd have to prove that their behavior met the standard criteria for sleep: decreased activity that is rapidly reversible, unlike a coma or unconsciousness; reduced responsiveness to stimuli compared to a waking state; and homeostatic regulation, meaning there is some sort of innate "drive" toward sleep and that the animal needs sleep to function. [10 Things You Didn't Know About the Brain]

To measure activity, the researchers counted the rate of the bell's pulsation in 23 jellyfish for six straight days and nights. They found that the rate dropped by 32 percent at night, going from about 1,155 pulses per 20 minutes during the day to 781 pulses per 20 minutes at night. When the researchers put a little midnight snack in the water column, the jellies perked up and started pulsing at daytime rates, indicating that this quiescent period was easily reversible.

But were the jellyfish less responsive than usual? To find out, the researchers put the jellyfish into small containers made of PVC pipe with a mesh bottom. They raised the jellies gently up from the bottom of the tank, then rapidly yanked the container downward, leaving the jellyfish suspended in the water.

Cassiopea jellies prefer sitting to swimming, so the suspended jellies pulsed their way down to the tank floor. But they did so much faster during the day, starting to pulse by 2 seconds after losing their resting surface, than they did at night, when it took them about 6 seconds to start pulsing — almost as if they were groggily shaking off sleep before they could react.

Next, the researchers tested whether the sleepy behavior in jellyfish was under homeostatic control. Put more simply, the question was: Would jellies act tired the next day if they were deprived of their quiescence at night? To find out, the researchers blew gentle pulses of water at the jellies for 10 seconds every 20 minutes. They found that when they disturbed the jellyfish this way during the last 6 hours of the night, the jellyfish showed a 12 percent decline in pulsing in the first 4 hours of the next day, as if they were having trouble waking up. When the researchers continued the disturbances all night, the jellyfish were 17 percent less active over the entire next day. After a full night without any disturbances, the jellyfish returned to normal activity levels the following day.

Evolution of sleep

One burning question is whether the sleep-like behavior in jellyfish is the same kind of behavior that eventually gave rise to the complex sleep of higher animals. Researchers do know that the same genes and molecules that control sleep in worms and flies also regulate sleep in zebrafish and humans, Nath said. The researchers weren't able to look for those genes and molecules in this study, but they did dose the jellyfish's water with melatonin and the antihistamine pyrilamine, two substances that make humans drowsy. The jellyfish, too, became less active in the presence of these substances, suggesting that the sleep state in the oldest known animals and in humans might have the same biological roots.

"If this is something that is conserved in what we observe in other invertebrates, vertebrates or humans, then what is the common denominator?" Bedbrook said. "What do they all have in common that could be the reason these animals go through this sleep state?"

The next step, Nath said, might be to use electrodes to track the activity of the jellyfish's neurons during the sleep-like state.

"We'd love to see whether there are other species of jellyfish that also sleep," Bedbrook added. "We would also like to see whether or not sponges, the next level down, sleep." Sponges don't have nervous systems at all, though they do possess some of the rudimentary genes and proteins found in other animals' nervous systems.

Original article on Live Science. 

People whose brains respond strongly to rewards may be less prone to some of the negative effects of sleep deprivation, a new study finds. One of those negative effects is depression, according to the study. Poor sleep has been linked to depression, both as a risk factor for the mental health disorder and as a symptom of it.

But not every person with sleep troubles has symptoms of depression, according to the study, published today (Sept. 18) in the Journal of Neuroscience.

Instead, differences in how people respond to positive experiences seem to have a "small but notable protective role" in stopping symptoms of depression from happening alongside sleep problems, said senior study author Ahmad Hariri, a professor of psychology and neuroscience at Duke University. [5 Surprising Sleep Discoveries]

In other words, people in the study who didn't sleep well but whose brain activity lit up in response to a reward were less likely to also have symptoms of depression than people who didn't sleep well and whose brain activity didn't light up as much in response to a reward.

"The extent to which you have a brain that's sensitive to reward and responses to rewarding experiences buffers against … the association between poor sleep and depression," Hariri told Live Science.

To study how the brain's response to rewards played a role in the link between poor sleep and depression, the researchers did brain scans on more than 1,100 college students. Before having their brains scanned, the students filled out questionnaires about how well they sleep at night and their mood.

During the brain scans, the students were asked to play a simple game so that the researchers could measure activity in an area of the brain called the ventral striatum, which is related to rewards. The ventral striatum acts as "the hub of reward learning," Hariri said; it's designed to learn what behaviors result in rewards and reinforce those behaviors.

In the game, which took about 6 minutes to play, the researchers asked the students to guess whether the number on a playing card was higher or lower than 5, and the students were told that the better they did, the more money they'd get. For each correct answer, the student would get positive feedback — "Hey, your guess was right!" — and the researchers would see how the ventral striatum responded. (Similarly, for wrong answers, the students would get negative feedback.) Unbeknownst to the students, the game was rigged — so during six rounds of the game, they would be right 80 percent of the time or wrong 80 percent of the time.

The researchers found that the extent to which a person's brain responded to a reward (or being told they got the right answer), the less likely that person would be to show an association between poor sleep and symptoms of depression, Hariri said. [7 Ways to Recognize Depression in 20-Somethings]

Other studies have shown that the ventral striatum plays a role in a range of symptoms of depression called "anhedonia," Hariri said. Anhedonia is basically "a fancy word for lack of pleasure," he said, and refers to symptoms such as not finding activities that were once rewarding to be pleasurable anymore, blunted emotions and a lack of motivation to participate in once-rewarding activities.

Interestingly, in the new study, the researchers found that activity in this area of the brain was linked to all symptoms of depression, not just anhedonia symptoms, Hariri said.

However, the study had some limitations, Hariri noted. For example, the researchers looked at only a snapshot in time. "What we don't have is that order of how things are happening," he said. It's unclear if a person's poor sleep came before or after symptoms of depression in the study, he said. Long-running studies are needed to confirm the findings.

Another limitation was that the research was done in relatively healthy young adults, so it's unclear if the findings would apply to older and less-healthy people.

Originally published on Live Science.

This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.

If you speak to someone who has suffered from insomnia at all as an adult, chances are good that person has either tried using marijuana, or cannabis, for sleep or has thought about it.

This is reflected in the many variations of cannabinoid or cannabis-based medicines available to improve sleep – like Nabilone, Dronabinol and Marinol. It’s also a common reason why many cannabis users seek medical marijuana cards.

I am a sleep psychologist who has treated hundreds of patients with insomnia, and it seems to me the success of cannabis as a sleep aid is highly individual. What makes cannabis effective for one person’s sleep and not another’s?

While there are still many questions to be answered, existing research suggests that the effects of cannabis on sleep may depend on many factors, including individual differences, cannabis concentrations and frequency of use.

Cannabis and sleep

Access to cannabis is increasing. As of last November, 28 U.S. states and the District of Columbia had legalized cannabis for medicinal purposes.

Research on the effects of cannabis on sleep in humans has largely been compiled of somewhat inconsistent studies conducted in the 1970s. Researchers seeking to learn how cannabis affects the sleeping brain have studied volunteers in the sleep laboratory and measured sleep stages and sleep continuity. Some studies showed that users’ ability to fall and stay asleep improved. A small number of subjects also had a slight increase in slow wave sleep, the deepest stage of sleep.

However, once nightly cannabis use stops, sleep clearly worsens across the withdrawal period.

Over the past decade, research has focused more on the use of cannabis for medical purposes. Individuals with insomnia tend to use medical cannabis for sleep at a high rate. Up to 65 percent of former cannabis users identified poor sleep as a reason for relapsing. Use for sleep is particularly common in individuals with PTSD and pain.

This research suggests that, while motivation to use cannabis for sleep is high, and might initially be beneficial to sleep, these improvements might wane with chronic use over time.

Does frequency matter?

We were interested in how sleep quality differs between daily cannabis users, occasional users who smoked at least once in the last month and people who don’t smoke at all.

We asked 98 mostly young and healthy male volunteers to answer surveys, keep daily sleep diaries and wear accelerometers for one week. Accelerometers, or actigraphs, measure activity patterns across multiple days. Throughout the study, subjects used cannabis as they typically would.

Our results show that the frequency of use seems to be an important factor as it relates to the effects on sleep. Thirty-nine percent of daily users complained of clinically significant insomnia. Meanwhile, only 10 percent of occasional users had insomnia complaints. There were no differences in sleep complaints between nonusers and nondaily users.

Interestingly, when controlling for the presence of anxiety and depression, the differences disappeared. This suggests that cannabis’s effect on sleep may differ depending on whether you have depression or anxiety. In order words, if you have depression, cannabis may help you sleep – but if you don’t, cannabis may hurt.

Future directions

Cannabis is still a schedule I substance, meaning that the government does not consider cannabis to be medically therapeutic due to lack of research to support its benefits. This creates a barrier to research, as only one university in the country, University of Mississippi, is permitted by the National Institute of Drug Abuse to grow marijuana for research.

New areas for exploration in the field of cannabis research might examine how various cannabis subspecies influence sleep and how this may differ between individuals.

One research group has been exploring cannabis types or cannabinoid concentrations that are preferable depending on one’s sleep disturbance. For example, one strain might relieve insomnia, while another can affect nightmares.

Other studies suggest that medical cannabis users with insomnia tend to prefer higher concentrations of cannabidiol, a nonintoxicating ingredient in cannabis.

This raises an important question. Should the medical community communicate these findings to patients with insomnia who inquire about medical cannabis? Some health professionals may not feel comfortable due to the fluctuating legal status, a lack of confidence in the state of the science or their personal opinions.

At this point, cannabis’s effect on sleep seems highly variable, depending on the person, the timing of use, the cannabis type and concentration, mode of ingestion and other factors. Perhaps the future will yield more fruitful discoveries.

Deirdre Conroy, Clinical Associate Professor of Psychiatry, University of Michigan

This article was originally published on The Conversation. Read the original article.

An online therapy program designed to treat insomnia also appears to reduce levels of anxiety and depression, a new study from the United Kingdom finds.

Sleep problems are common in people who also have mental health conditions, including anxiety and depression. In fact, sleep issues are often thought to be a symptom of these other issues, according to the study. But the new findings suggest that the opposite may be true: Some mental health conditions may stem from a lack of sleep.

"How well we sleep might actually play a role in our mental health," lead study author Daniel Freeman, a professor of clinical psychology at the University of Oxford, said in a statement. "If you can sort out your sleep, you could also be taking a significant step forward in tackling a wide range of psychological and emotional problems." [Get Better Sleep in 2017]

The new study, which was published today (Sept. 6) in the journal The Lancet Psychiatry, included more than 3,700 British college students (with an average age of 24) who had insomnia. All participants filled out questionnaires about their sleep and other mental health conditions — including paranoia, hallucinations, anxiety and depression — at the beginning of the study and then again after three and 10 weeks, when the treatment ended. Twelve weeks later, the participants filled out the questionnaires for the final time.

The people in the study were randomly assigned to either the treatment group or the control group. Those in the treatment group participated in an online cognitive behavioral therapy (CBT) program. CBT focuses on the way people think, and helps them challenge their own thoughts and beliefs; a specialized type of CBT for insomnia, called CBT-I, is considered to be a "first-line" therapy for people with insomnia that lasts longer than one month, according to the American College of Physicians. The people in the control group did not receive CBT.

The online program involved six 20-minute-long sessions, and the participants were asked to keep a sleep diary, practice certain behavioral techniques and learn about healthy sleep, according to the study. Using data from the sleep diaries, the program tailored its advice to each participant.

The researchers found that after 10 weeks, the people in the treatment group reported less insomnia, fewer hallucinations and fewer experiences of paranoia than those in the control group. In addition, the people in the treatment group had decreased levels of depression and anxiety, and improved psychological well-being and perceived functioning, compared with the people in the control group. ("Perceived functioning" refers to how well the people thought they were functioning on a daily basis.) Further analysis showed that 60 percent of the decrease in paranoia levels could be linked to improved sleep, the study found.

The findings suggest that sleep plays an important role in mental health and that doctors should consider it a priority to improve patients' sleep, the authors wrote.

"For too long, insomnia has been trivialized as merely a symptom" of other mental health conditions, and has been thought of as a problem to be tackled, Freeman said. But "for many people, insomnia can be part of the complex package of causes of mental health difficulties," he said. 

The researchers noted that the study had limitations. For example, many people did not complete the study, so it's unclear if the findings would apply to larger groups of people, the researchers said. Only half of the participants logged in to two therapy sessions, and just 18 percent logged in to all six sessions. In addition, the participants self-reported their symptoms, which can be an unreliable method, the researchers said.

More research is also needed to see how long the effects of the CBT online therapy last, the researchers said.

Originally published on Live Science.

Consider it another strike against not getting enough sleep: A new study finds that getting too little REM sleep may be linked to a higher risk of dementia later in life.

REM, or "rapid eye movement," sleep is one of four sleep stages, which also include two stages of light sleep and a stage of deeper sleep called slow-wave sleep. REM sleep is characterized by vivid dreams and high levels of brain activity, similar to the brain's state when its awake. Humans typically cycle through several periods of REM sleep between the other stages of sleep each night.

In the new study, published today (Aug. 23) in the journal Neurology, researchers found that the people who developed dementia had gotten significantly less REM sleep when examined overnight years earlier compared with the people who didn't develop cognitive problems. [Get Better Sleep in 2017]

The study does not prove that low levels of REM sleep cause dementia; rather, it shows an association between the two, said lead study author Matthew Pase, a senior research fellow at Swinburne University of Technology in Australia.

Pase offered several ideas for how REM sleep and dementia might be linked.

"On one hand, REM may help protect connections within the brain that are vulnerable to damage with aging and Alzheimer's disease," Pase told Live Science. "On the other hand, perhaps lower REM is caused by other potential dementia risk factors, such as heightened anxiety and stress. This requires further study."

Doctors have long known that poor sleep can result in mental and emotional health problems. But details about which types of sleep are associated with dementia and long-term cognitive decline have been lacking. More than 10 percent of Americans over age 65 have some form of dementia, according to the Centers for Disease Control and Prevention.

In the new study, the researchers looked at more than 320 people in the U.S. whose average age was 67. These people were already part of an ongoing, larger study on heart health. The researchers collected sleep data approximately half way through the as they followed the participants for an average of 12 years. During that time, 32 people (about 10 percent) were diagnosed with some form of dementia; among those 32 people, 24 were diagnosed with Alzheimer's disease.

The people who developed dementia spent an average of 17 percent of their sleep time in REM sleep, compared with 20 percent for those who did not develop dementia. The researchers found that for every 1-percent reduction in REM sleep, there was a 9-percent increase in the risk of dementia. The results held up even after the researchers adjusted for other factors that could affect dementia risk or poor sleep, such as heart disease, depression and medication use.

Also, the time that the people spent in stages of non-REM sleep was not associated with dementia risk, the study found. [5 Surprising Sleep Discoveries]

"The study is valuable, since it has identified inadequate REM sleep as correlating with dementia risk," said Dr. Pinky Agarwal, a neurologist at EvergreenHealth in Washington and a professor of neurology at the University of Washington. Agarwal was not part of the study.

"The current [scientific] literature is mixed and mostly identifies inadequate 'slow wave sleep' [a type of deep, non-REM sleep] as a risk, but these have been much shorter-duration studies," Agarwal told Live Science. Because REM sleep is thought to be related to how the brain processes and retains memories, the new findings make sense, she said; dementia is, in part, marked by memory problems. The research points to the need for closer follow-up to recognize signs of dementia in patients with decreased REM sleep, she added.

Indeed, Pase noted that his research group would like to understand why a lower amount of REM sleep is tied to an increased risk of dementia. He hopes to tap into a larger sample of data to examine the relationship between sleep and signs of accelerated brain aging, such as poor thinking, memory problems and loss of brain volume.

This further research might provide more information about how getting less REM sleep, or even poor sleep in general, could lead to the development of dementia, Pase said.

Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.

Live Science is bringing our readers a monthly series on personal health goals. We'll give you tips and tricks for reaching those goals, based on the advice we've gathered from the countless health experts we've interviewed. Each month, we'll focus on a different goal, and the goal for August is "Get Better Sleep." Follow us on Facebook and Twitter to connect with other readers who are working toward these goals.

Jump to: January — Lose Weight | February — Eat Healthy | March — Start Exercising | April — Cope with Allergies | May — Protect Yourself from Sun and Heat | June — Stay in Shape Outdoors | July — Get Gutsy About Gut Health

Falling asleep — sounds simple, right? But for people who struggle to fall asleep or stay asleep through the night, or for those who can't stop hitting the snooze button in the morning, getting good sleep can feel pretty complicated. On this page, Live Science brings you the science behind sleeping more soundly. We've rounded up our best reporting, from bedtime tips to the latest studies on the science of sleep, to help you get the shut-eye you need.

Why sleep?

For starters, why do we even need to sleep in the first place? The answer is a bit murkier than you simply sleep because you feel tired. In fact, why people need sleep remains somewhat of an unsolved mystery in science. But research has shed some light on the reason for our slumbers, including that sleep may help the brain cleanse itself of toxins at night.

More info:

• Why Do We Sleep?
• A Night's Sleep Cleans Brain of Harmful Toxins
• The Longest Night: Do We Sleep Better on the Solstice?

And although the exact reason for sleep remains unknown, scientists do know a bit (though not everything) about what goes on while a person sleeps. Experts break down sleep into several stages, known as the stages of sleep. Here's what goes on in each of them:

• REM vs. Non-REM Sleep: The Stages of Sleep

Falling asleep and staying asleep

Some scientists compare the process of falling asleep to a computer shutting down: The brain goes through a series of steps, "shutting down" certain areas as sleep sets in. But what can help a person fall asleep, and then stay asleep? And how much sleep do you actually need?

More info:

• How Do We Fall Asleep?  
• How Much Sleep Should You Get? New Recommendations Released
• How Much Sleep Does Your School-Age Child Need?
• Busting the 8-Hour Sleep Myth: Why You Should Wake Up in the Night
• How Long You Sleep May Be in Your Genes  
• Why Does the Sound of Water Help You Sleep?                     
• 'Super Sleepers' May Actually Be Sleep Deprived
• 5 Surprising Sleep Discoveries  

All about insomnia

More than 1 in 4 Americans say they don't get enough sleep from time to time, and nearly 1 in 10 say they have chronic insomnia, according to the Centers for Disease Control and Prevention (CDC). But what, exactly, does it mean to have insomnia? People with insomnia may have trouble falling asleep at night, or they may have trouble staying asleep, the CDC says. Some people with insomnia may wake up too early in the morning, and they may be unable to fall back to sleep.

More info:

• Insomnia: Symptoms, Treatment & Prevention  
• 7 Strange Facts About Insomnia
• Brain Scans May Reveal How People with Insomnia May Be Wired Differently
• Procrastinators Beware: Insomnia Linked with Putting Things Off
• Insomnia Can Worsen Chronic Pain Conditions 
• Log On, Sleep Better? Online Therapy for Insomnia Shows Promise   

Sleep apnea

Sleep apnea is another common sleep disorder — but people don't always know they have it, because the condition often goes undiagnosed, according to the National Heart, Lung and Blood Institute (NHLBI). People with sleep apnea experience short pauses in their breathing during sleep, often because the breathing tube closes or becomes blocked. These pauses can last a few seconds to a few minutes and typically end with a loud snoring or gasping sound. Although the condition sounds frightening, many people with it don't realize they have it, simply because they continue to sleep through the night. But sleep apnea takes a toll: The condition causes people to shift out of deep, restorative sleep and into light sleep, the NHLBI says.

More info:

• Sleep Apnea: Symptoms, Causes and Treatments
• Sleep Apnea Linked with Silent Strokes
• How I Can Tell If I Have Sleep Apnea?
• Kids with Sleep Apnea More Likely to Develop Behavioral Problems
• Breathing Problems During Sleep Linked with Cancer

How sleep affects your health

Not getting enough sleep can be a drag if it happens once in a while, but if you miss out on it regularly, the effects can build up and take a serious toll on your health. Recent research has shown that sleep deprivation can increase a person's risk of diseases such as heart disease and type 2 diabetes.

More info:

• Why Sleep Is So Important for People at Risk for Heart Disease
• The Spooky Effects of Sleep Deprivation
• Lack of Sleep May Boost Diabetes Risk
• Getting Too Little Sleep Raises Hunger Levels

Benefits of a good night's rest

On the other hand, getting a good night's rest can do wonders for your health, from improving your mood and appearance to even giving the brain a chance to reset its neural networks to prepare for the day ahead. Here's the latest on the benefits of sleep:

• Sleeping Beauty: Science Proves Beauty Rest Is Real
• Sleeping Shrinks the Brain, and That's a Good Thing
• Hit the Sack! People Who Get a Good Night's Sleep Are Happier
• Sleep Is Important to Weight Loss, Research Suggests
• After a Good Night's Sleep, Brain Cells Are Ready to Learn

Seriously — get your tech out of the bedroom

Are smartphones, tablets and laptops ruining your sleep? A slew of science studies point to a pretty clear "yes." Certain types of light from these devices can trick the brain into thinking it's daytime, suppressing the brain's release of the sleep hormone melatonin. Experts agree: The best way to put a stop to this particular sleep obstacle is to simply keep your tech devices out of the bedroom.

More info:

• How Blue LEDs Affect Sleep
• More Science Says Smartphones Spoil Sleep
• For Teens, Falling Asleep Gets Harder with More Screen Time
• Touch Screens May Be Ruining Toddlers' Sleep
• Apple's 'Night Shift' Mode: How Smartphones Disrupt Sleep

Strange sleep conditions

For some people, sleep troubles can stem from conditions beyond insomnia and sleep apnea. These sleep conditions can sound strange and frightening — and, in some cases, such as sleep paralysis or "exploding head syndrome," they are. Here's the lowdown on a few of the stranger things that can go wrong during sleep.

More info:

• The Demon on Your Chest and Other Terrifying Tales of Sleep Paralysis
• Hearing Crashes, Seeing Light: Life with Exploding Head Syndrome
• Should You Wake Up a Sleepwalker?
• Why Do People Talk in Their Sleep?
• Strange Sleep Disorder Makes People Appear 'Totally Drunk'
• Top 11 Spooky Sleep Disorders

Originally published on Live Science.

Scientists once thought that sleep was a passive state, a time when a person's brain and body shut down for the night to rest and recover. But now, researchers know that sleep is a highly active time, a period during which the brain and some physiological processes may be hard at work. 

For example, some hormones involved in growth in children, cell repair or digestion are boosted during sleep. Brain pathways involved in learning and memory also increase, according to the National Institutes of Health (NIH). 

In fact, the brain is sometimes more active when a person is asleep than when he or she is awake, according to Harvard Medical School. But sleep can also slow down many other physiological processes, from heart rate and breathing to body temperature and blood pressure. 

The stage of sleep a person is in also affects how active the brain and body are. 

For more than 60 years, sleep researchers have known that there are two major categories of sleep: REM sleep, which stands for "rapid eye movement," and non-REM or non-rapid eye movement sleep, said Dr. Stuart Quan, clinical director of the division of sleep and circadian disorders at Brigham and Women's Hospital in Boston. 

Non-REM sleep is now considered to consist of three stages, known as N1, N2 and N3, Quan said. Before 2007, non-REM sleep was broken down into four stages, but then sleep medicine specialists decided that there was no physiological reason to distinguish between two of the stages, the old stage 3 and stage 4 sleep, he explained. Those were combined into one stage, now referred to as N3. 

During sleep, the brain repeatedly cycles through four distinct stages of REM and non-REM sleep in a specific sequence. This sequence changes somewhat between the first and second half of sleep. As sleep progresses in a series of four to five sleep cycles throughout the night, the time spent in the REM stage gets longer and the time spent in N3 sleep gets shorter, Quan said.  

Live Science asked Quan for a more detailed explanation of what happens in the body and brain during each of these four stages of sleep.  

Non-REM sleep

Stage N1

When a person gets drowsy, he or she is drifting into N1 sleep, Quan said. In this first stage of non-REM sleep, a person is making the transition from being awake to falling asleep. 

This is a relatively light form of sleep that lasts about 5 to 10 minutes. During this stage, heart and breathing rates begin to slow, eye movements also slow, and muscles relax. Body temperature decreases, and brain waves, if observed on an electroencephalogram (EEG) in a sleep lab, would be seen to slow. 

A person can be easily awakened from N1 sleep, and that individual may not think he or she had been asleep, Quan said. N1 sleep is the first stage entered when taking a nap. 

It's normal for a person to experience "hypnic jerks," also known as "sleep starts," during N1 sleep, Quan said. This is a sudden, brief muscle jerk that may happen along with a falling sensation when a person is in bed, he said. When it occurs, this sudden movement may or may not wake a sleeper up. 

Adults spend the least amount of time in stage N1 sleep, which represents about 5 percent of their total sleep time, Quan said. 

Stage N2

Shortly after N1 sleep ends, a person enters this second stage of non-REM sleep, which typically lasts 10 to 25 minutes, Quan told Live Science. It's also considered a period of light sleep. 

During this stage, eye movement stops, heart rate slows, brain waves become slower and muscles relax even further. 

As sleep cycles repeat throughout the night, a person spends more time in stage N2 sleep than in any other sleep stage, according to the National Institutes of Health. Adults spend about 55 percent of their total sleep time in stage N2 sleep, Quan said.

Stage N3

Non-REM sleep then progresses into its third stage, which is often referred to as "slow wave," "delta" or "deep" sleep. ("Delta" waves are a type of slow brain wave typically seen during this stage on EEG in a sleep lab.)

N3 sleep is a period of deep sleep that is needed for an individual to feel refreshed for the next day. A person typically spends more time in the N3 stage during the first half of sleep than the second half, but why this happens is not known. 

Typically lasting 20 to 40 minutes, N3 sleep is when the brain becomes less responsive to external stimuli, and as a result, it is most difficult to wake a person up from this stage, Quan said. Someone awakened from N3 sleep is extremely groggy and disoriented, Quan said.

This grogginess is one reason why people may not want to nap for more than 30 minutes, because they can drop into N3 sleep, Quan said. 

During N3 sleep, heart rate and breathing slow to their lowest levels during sleep. Blood pressure falls, and body temperatures drops even slower. Muscle activity decreases, and there is no eye movement. Blood pressure falls but not to a dangerous extent, Quan explained. 

He said that this is also the stage when sleepwalking and sleep talking are most likely to occur. "Nightmares and night terrors are also N3 sleep phenomenon," Quan said. (Night terrors, also called sleep terrors, typically occur in children and involve a child sitting up in bed during sleep and screaming, according to the Mayo Clinic.)

Slow-wave sleep occurs for longer stretches in babies and young children, and the time spent in N3 sleep decreases steadily with age for reasons that are unclear, Quan said. 

Adults typically spend about 15 percent of their total sleep time in stage N3, Quan said. 

REM sleep

A person first enters REM sleep about 90 minutes after falling asleep and going through all three stages of non-REM sleep, Quan said. The first REM cycle of the night typically lasts about 10 minutes, but each subsequent REM stage gets progressively longer as the night goes on, he said. 

The characteristic sign of REM sleep is that a person's eyes move rapidly from side to side beneath closed eyelids. 

Although this eye movement is not constantly occurring, scientists don't know exactly why it takes place, although some have speculated that it's linked with dreaming. 

Supporting that idea, REM sleep is the stage when most dreaming and vivid imagery occurs, Quan told Live Science. People often don't remember much of their dreams, but they are more likely to recall some aspects of a dream if awakened from REM sleep, he said. 

During this kind of sleep, heart rate increases and blood pressure rises slightly compared with N1 sleep. Body temperature falls to its lowest point during sleep. Arm and leg muscles deeply relax to the point of being almost immobile, possibly to prevent people from acting out their dreams, according to the Mayo Clinic. 

Breathing becomes fast and shallow, and the brain may be even more active during this stage of sleep than during wakefulness, sleep experts say. REM sleep is when the brain processes information from the day so it can be stored in long-term memory, according to the National Sleep Foundation, a nonprofit group that educates the public about sleep. 

A newborn baby may spend about 80 percent of his or her total sleep time in REM-stage sleep, while infants spend at least 50 percent of their sleep time in REM sleep, according to the NIH. In comparison, most adults spend 20 to 25 percent of their total sleep time in REM sleep, Quan said. 

The proportion of time spent in this state of sleep stays relatively constant throughout adulthood, but it may drop in people age 65 and older, Quan said. He added that sleep tends to be lighter in older adults, who experience more "microarousals," or blips into wakefulness. But these brief awakenings do not affect whether an older adult does or does not feel refreshed in the morning, Quan said.

Humans spend nearly a third of their lives asleep. Going without sleep will literally make you psychotic and, eventually, kill you. It's clear that shut-eye is crucial to the body's ability to function.

But no one knows what sleep actually does.

"It's sort of embarrassing," said Dr. Michael Halassa, a neuroscientist at New York University. "It's obvious why we need to eat, for example, and reproduce … but it's not clear why we need to sleep at all." [5 Surprising Sleep Discoveries]

We're vulnerable when we're asleep, so whatever sleep does, it must be worth the risk of the brain taking itself mostly offline. There are a few theories about why we sleep, and although none of them are totally solid, a few try to explain what happens each night, pulling in research on topics ranging from cellular processes to cognition. Researchers say it does seem clear that sleep is key to the brain's ability to reorganize itself — a feature called plasticity.

Sleep stages

It's not hard to prove that sleep is important. Rats totally deprived of sleep die within two or three weeks, according to research by the pioneering University of Chicago sleep scientist Allan Rechtschaffen. No one has done similar experiments on humans, for obvious reasons, but a 2014 study published in The Journal of Neuroscience found that a mere 24 hours of sleep deprivation caused healthy people to have hallucinations and other schizophrenia-like symptoms.

One reason it is difficult to get a handle on why we sleep is that sleep is actually pretty difficult to isolate and study. Sleep-deprivation studies are the most common way to study sleep, said Marcos Frank, a neuroscientist at the University of Washington, but depriving an animal of sleep disrupts many of its biological systems. It's hard to tell which outcomes are directly attributable to sleep deprivation rather than, say, stress.

Another reason sleep is hard to understand is that the brain may be doing two different things during the two major stages of sleep. As the night wears on, sleepers cycle through non-rapid eye movement (non-REM) and rapid-eye-movement (REM) sleep. Non-REM sleep is marked by slow brain waves called theta and delta waves. In contrast, the brain's electrical activity during REM sleep looks much like it does when a person is awake, but the muscles of the body are paralyzed. (If you've ever experienced sleep paralysis, it's because you woke from REM sleep before this paralysis ended.)

Studies have found differences in the biology of the brain during these different stages. For example, during non-REM sleep, the body releases growth hormone, according to a 2006 review of the biology of sleep published by Frank in the journal Reviews in the Neurosciences. Also during non-REM sleep, the synthesis of some brain proteins increases, and some genes involved in protein synthesis become more active, the review found. During REM sleep, in contrast, there does not appear to be any increase in this sort of protein-producing activity.

What do we know about sleep?

One conclusion that has emerged from sleep research is that sleep does appear to be largely a brain-focused phenomenon, Frank said. Although sleep deprivation affects the immune system and alters hormone levels in the body, its most consistent impacts across animals are in the brain. [10 Things You Didn't Know About the Brain]

"The central nervous system is always impacted by sleep," Frank said. "There may have been other things that evolution added onto the primary function of sleep, but the primary function of sleep probably has something to do with the brain."

There is some evidence, in fact, that sleep is just something that neurons do when they're joined in a network. Even neuron networks grown in lab dishes show stages of activity and inactivity that sort of resemble waking and sleeping, Frank said. That could mean sleep arises naturally when single neurons begin to work together.

This could explain why even the simplest organisms show sleep-like behaviors. Even Caenorhabditis elegans, a tiny worm with only 302 neurons, cycles through quiet, lethargic periods that look like sleep. Perhaps the first simple nervous systems to evolve exhibited these quiet periods, Frank said, and as brains got larger and more complex, the state of inactivity also had to get more complicated.

"It would be very disadvantageous to have a complex brain like ours where different parts are falling in and out of sleep, so you need to have some way to orchestrate this," he said.

What happens during sleep?

But the idea that sleep is a natural property of neuron networks doesn't really explain what's going on during sleep. On that front, scientists have a number of theories. One is that sleep restores the brain's energy, according to a 2016 review in the journal Sleep Medicine Reviews. During non-REM sleep, the brain consumes only about half the glucose as it does when a person is awake. (Glucose is the sugar that cells burn up to release energy.)

But if the idea that sleep restores brain energy is true, the relationship between sleep and the brain's energy usage is not straightforward. For example, during sleep deprivation, the brain's breakdown of an energy source called glycogen increases in some parts of the brain but decreases in others. More research is needed to understand this link. [The 7 Biggest Mysteries of the Human Body]

Another idea is that sleep might enable the brain to clear out toxic products produced when we're awake. The brain is a huge consumer of energy, which means it also produces much waste. Some recent research suggests that sleep is a time when the brain sweeps itself clean, Frank said, but those results need to be replicated.

"It might be something that kind of happens with sleep," Frank said, "but it may not be the most important thing sleep is doing."  

Perhaps the most promising theory of sleep so far is that it plays a major role in the brain's connectivity and plasticity. Plasticity is involved in learning and memory. Although it's unclear exactly how, plenty of evidence suggests that losing sleep can cause problems with memory, particularly working memory, the process that allows people to hold information in an easily accessible way while working out a problem. People who are sleep-deprived also struggle with choosing what to pay attentionto and regulating their emotions.

One way sleep may affect the brain's plasticity is through its effects on the synapses, or connections between neurons. Research has shown that when animals learn a new task, their neurons seem to strengthen the synaptic connections involved in learning that task during the next sleep cycle, according to the Sleep Medicine Reviews paper. In experiments where researchers put a patch over one of an animal's eyes, the brain circuits associated with visual information from that eye weakened within hours, according to research by the University of Surrey's Julie Seibt and colleagues. REM sleep, however, strengthened the circuits involving the other eye, suggesting that the brain uses sleep to adjust to changing inputs. [7 Weird Facts About Balance]  

"It could still mean there is something really basic and central at the heart of [sleep], something basic that brain cells have to do, and one outcome is the plastic change," Frank said.

In the future, a better understanding of sleep may come from research on cells called glia cells, Frank said. These brain cells, whose name literally means "glue," were once thought to be largely inert but have been recently discovered to have a range of functions. Glia cells outnumber neurons by up to three to one, Frank said. Glia cells may control the flow of cerebrospinal fluid throughout the brain, which could result in clearing out metabolic waste during sleep, for example.

"It could be that the mystery of sleep could be solved by understanding what these very specialized glia cells are doing," Frank said.

Original article on Live Science. 

The Science of Jet Lag: 5 Surprising Findings

Nothing can throw off the start of a fun vacation faster than jet lag.

Travelers who feel groggy in the afternoon or wake up well before sunrise can blame both things on the body's biological clock falling out of sync with the time on the person's watch.

A "master clock" in the brain called the suprachiasmatic nucleus controls the body's circadian rhythm. This clock responds to external signals — most notably, sunlight — to sync the body's internal timing with that of the environment.

How far you travel and where you go can affect how well your body responds to these disruptions. Read on to learn more about jet lag. 

It's harder to adjust when you fly east

If you recover from jet lag faster when you travel west, you're not alone: The brain has an easier time adjusting to westward travel compared with eastward travel, according to a 2016 study in the journal Chaos.

This is due to a small quirk in the cells in the body that control the biological clock, or circadian rhythm: These cells don't operate on a perfect 24-hour schedule. Instead, the cells' daily cycle is closer to 24.5 hours.

Because the cells that control the body's clock operate on a slightly longer day, it's easier to travel in a direction that extends the length of the day — in other words, to travel west across time zones. Flying east across time zones, on the other hand, results in a shortening of the day, so it is more difficult for the body to adjust.

Here's how long you really need to recover

According to widely touted advice, you should give yourself one day to recover from jet lag for every time zone you cross. This would mean that if a person flew from New York City to Los Angeles — a trip that spans three time zones — he or she would recover from jet lag in three days.

But in the same 2016 study from the journal Chaos, researchers tested this idea using mathematical models.

They found that jet-lag recovery doesn't quite fit into the neat pattern of one day per time zone.

Instead, when traveling west, it would take a person a little less than four days to recover from crossing three time zones, six days to recover from crossing six time zones, just under eight days for crossing nine time zones and around nine days for crossing 12 time zones.

However, when traveling east, the adjustment periods are longer: It takes a little more than four days to recover from crossing three time zones, more than eight days to recover from crossing six time zones, more than 12 days for crossing nine time zones and around nine days for crossing 12 time zones. 

Scientists are looking for weird ways to fight jet lag

One of the most commonly cited remedies for resetting the body's clock is exposure to bright light early in the morning. And although this tried-and-true method does help, scientists are still looking for more solutions to jet lag.

In an April 2017 study in The Journal of Physiology, for example, researchers reported that cells in the eyes of rats produce a molecule called vasopressin that travels to the brain and helps regulate the biological clock. More studies need to be done in humans to confirm these results, the researchers said. But this finding could allow scientists to develop eye drops that trigger these eye cells to produce the molecule, helping people recover from jet lag, they said.

And in an October 2016 study in the journal Cell Metabolism, researchers reported that small shifts in oxygen levels in the air could help reset the biological clock in mice. In that study, researchers found that mice that were exposed to air with slightly lower levels of oxygen than normal adjusted more quickly to a new circadian rhythm than mice that received steady levels of oxygen.

And although lower levels of oxygen might sound scary, the concentrations used in the study were actually similar to the concentration of oxygen that people breathe on airplanes, the researchers said.

More research, especially in humans, is needed to confirm these findings, the researchers said, adding that they would also like to see if higher levels of oxygen have a similar effect.

Jet lag isn't caused only by jet setting

Changes in your social schedule, even when you stay at home, can also cause your body's internal clock to fall out of sync.

This phenomenon, known as "social jet lag," often occurs when people keep a different schedule on weekdays compared with the weekend. For example, going to bed every night at 10 p.m. and waking up at 6 a.m. during the workweek, but going to bed at 1 a.m. and sleeping until 10 a.m. on the weekend can cause a mismatch between the biological clock and the actual time.

But social jet lag doesn't mean just that it's more difficult to get up on Monday morning after a weekend of late nights and sleeping in; research has shown that social jet lag may harm a person's health.

For example, a 2015 study from the International Journal of Obesity found that people who had greater discrepancies between their weekend and weekday sleep schedules were more likely to weigh more and have problems with their metabolisms, compared with people whose sleep schedules didn't change between the weekend and weekdays. 

When you eat could influence your biological clock

Jet lag doesn't just mess with when you fall asleep and when you wake up; it can also have more subtle effects on the body. For example, jet lag and shift work can cause the body's "master" clock in the brain to fall out of sync with "peripheral" clocks located throughout the body. These peripheral clocks are essentially molecules in cells that respond to the master clock and help control certain bodily functions.

One of the functions affected by these clocks is the control of blood sugar levels. The way the body responds to food varies throughout the day. Eating a meal at night, for example, leads to a greater rise in blood sugar levels compared with eating a meal earlier in the day.

In a study reported in June 2017, researchers found that by shifting the time of day that a person eats, they could also shift the rhythm of that person's blood sugar levels, meaning that normal fluctuations occurred later in the day than they usually would.

These findings suggest that changing your meal time — in addition to taking other steps to adjust to jet lag, including exposure to light at the appropriate time — could help you adjust to different time zone or work schedule.

Originally published on Live Science.

Trouble sleeping may take a bigger toll on women than on men, a new study from Australia finds.

Women in the study were more likely than men to have sleep disorders that made them feel tired during the day, the researchers found. And women were also more likely to have trouble with memory and concentration due to sleepiness.

"We found that females were more likely to have sleeping disorders associated with daytime sleepiness," study co-author Dr. John Malouf, the founder of the SleepGP sleep clinic in Coolangatta, Australia, said in a statement. "Females were also likely to feel more affected by the burden of their symptoms." [5 Surprising Sleep Discoveries]

In the study, which was published in May in the Journal of Clinical Sleep Medicine, the researchers looked at data on nearly 750 adults in Australia who had sought medical care for sleep problems between April 2013 and January 2015. At the time, the people filled out questionnaires about their sleep and overall health.

For example, the questionnaires asked if the people ever had trouble falling asleep and if they felt excessively tired or sleepy during the day. One question asked if the people had trouble concentrating during the day because of sleepiness. In addition, the researchers wanted to know if the participants or their partners snored.

One-third of all people in the study said that they had trouble falling asleep at night, though this was more common among the women than the men. Nearly half of the women reported problems falling asleep, compared with just 27 percent of men.

The women in the study also reported more problems during the day as a result of their sleep problems at night.

For example, nearly half of the women in the study, 49 percent, said they had sleep problems that caused daytime sleepiness, while 37 percent of the men in the study said the same. The researchers also found that 77 percent of the women felt excessively sleepy or tired during the day, compared with 66 percent of the men.

Daytime sleepiness had a significant effect on the women's ability to concentrate during the day; 89 percent of the women said they had trouble concentrating because they were tired, compared with 74 percent of men. And 80 percent of women said that being sleepy led to memory problems, compared with 58 percent of men, the study found. [7 Strange Facts About Insomnia]

The reasons behind these differences between the sexes are unclear, and more research is needed to explore possible reasons, the researchers said. However, previous studies have suggested that hormonal factors as well as anatomical and physiological differences between men and women may play a role, the study said.

Women in the study also seemed to be more affected by their partners' snoring, the research said. Snoring men were more likely to keep their partners awake than snoring women were.

This was particularly apparent when the researchers asked the participants if their snoring had ever forced their partners out of the bedroom. The scientists found that 63 percent of the men who said their snoring kept their partners awake also said that the snoring forced their partners the room; 54 percent of the women who said their snoring kept their partners awake also said that the snoring forced their partners out of the room.

Though the reasons behind the findings on snoring are unclear, it is possible that women are simply more sensitive to their partners' snoring and men have a higher tolerance for their partners' snoring, the researchers said.

Originally published on Live Science.

For people who are at risk for heart disease and diabetes, getting enough sleep may be especially important: Snoozing for less than 6 hours per night may increase their risk of premature death, a new study finds.

People in the study who had a high body mass index (BMI) and elevated cholesterol along with a few other risk factors for heart disease and diabetes — a combination called metabolic syndrome — and slept less than 6 hours per night were twice as likely to die of heart disease or stroke over a nearly 17-year period as people without the syndrome, the researchers found.

People with metabolic syndrome who slept at least 6 hours per night also had a higher risk of dying over the same time period than people without the syndrome, the scientists found. However, this risk was not as high as it was among the people who slept less than 6 hours per night and also had metabolic syndrome, according to the study. [5 Surprising Sleep Discoveries]

"If you have several heart disease risk factors, taking care of your sleep and consulting with a clinician if you have insufficient sleep is important if you want to lower your risk of death from heart disease or stroke," lead study author Julio Fernandez-Mendoza, an assistant professor of psychiatry at Penn State College of Medicine, said in a statement.

In the study, the researchers looked at 1,344 adults whose average age was 49. The researchers invited the people to sleep at a lab for one night, during which they observed how long the people slept. At the lab, the researchers also looked at whether the participants had metabolic syndrome. The syndrome was defined as a combination of a BMI higher than 30, and elevated levels of cholesterol, blood pressure, blood sugar and blood fats called triglycerides. Of all the people in the study, 39.2 percent had the syndrome.

Then, the researchers followed the people for nearly 17 years. During this time, 22 percent of the participants died, according to the study, which was published today (May 24) in the Journal of the American Heart Association.

The researchers looked at the relationship between metabolic syndrome, how long the participants slept at the study's start and their risk of death during the 17 years. They found that the people with metabolic syndrome who slept at least 6 hours at the start of the study were 1.5 times more likely to die of cardiovascular disease or stroke than the people who did not have metabolic syndrome. [Where Is Heart Disease Risk the Highest and Lowest? (Maps)]

However, the people with metabolic syndrome who slept less than 6 hours at the start of the study were 2.1 times more likely to die of heart disease or stroke as the people without the syndrome.

Moreover, the people who slept less and also had metabolic syndrome were twice as likely to die from any cause during the study period as the people who did not have the syndrome. In comparison, the people with metabolic syndrome who slept 6 or more hours at the start of the study were 1.3 times more likely to die from any cause than the people without the syndrome.

Although the study shows a link between shorter sleep duration and mortality among people with metabolic syndrome, it does not prove that there is a causal relationship between the two, Fernandez-Mendoza said. In addition, more research is needed to understand the reasons for the link, he told Live Science.

Originally published on Live Science.

The air pollution around you could affect how well you sleep, a new study finds.

Researchers found that people in the study who lived in areas with high levels of air pollution were 60 percent more likely to sleep poorly, based on the measures used in the study, than those who lived in areas with cleaner air.

Chronic sleep deprivation has been linked with a range of health problems, the study said.

"Not having enough sleep and having low quality sleep affects people's performance, increases the risk of vehicle accidents, lowers mood," said Dr. Martha E. Billings, the lead author of the study and an assistant professor of medicine at the University of Washington. [5 Surprising Sleep Discoveries]

"Over time, there is a higher risk of cardiovascular diseases and cancer in people who are not getting adequate sleep, so there is a lot of implications as well as general well-being and the quality of life," Billings said.

The researchers used data from an ongoing study called the Multi-Ethnic Study of Atherosclerosis (MESA) to look for correlations between exposure to air pollution and the quality of sleep of 1,863 individuals in six U.S. cities. The researchers focused on two measures of sleep quality — sleep efficiency, which is the total amount of time actually spent asleep, and the frequency of awakenings after falling asleep.

The study participants wore actigraphy watches, which are similar to a FitBit. They detected how many times each person woke up during the night and how long they stayed awake, Billings said.

The researchers compared this data set with information about the concentrations of two major air pollutants around the participants' homes. They looked at nitrogen dioxide (NO2) and fine particulate pollution (PM2.5), meaning solid particles in the air that have a diameter of less than 2.5 micrometers. This information came from the Environment Protection Agency's monitoring sites across the U.S. in combination with local environment data and statistical modeling.

The researchers grouped the participants into quartiles based on the level of air pollution in their areas, Billings said. "We found that there was an about 60 percent higher odds of having a low sleep efficiency if you had an exposure in the highest quartile of air pollution."

Low sleep efficiency, as the researchers defined it in the study, meant being asleep less than 88 percent of the time spent in bed. The researchers found that the percentage of people suffering from low sleep efficiency as well as the total amount of time they were awake increased with the concentration of air pollution in their homes.

The study found an association, not a cause-and-effect relationship, between air pollution levels and sleep quality. Billings said the researchers don't know how air pollution may affect sleep, but there are many possible mechanisms in which air pollution could be causing people to toss and turn. [7 Strange Facts About Insomnia]

"It may be because they are exposed to more traffic noise that is disrupting their sleep," Billings said. "It could also be an effect of the air pollution itself that is causing airway irritation. Sometimes those small particles can get into the blood stream and that could affect regulation of sleep in the brain – that's our hypothesis, but we still need further studies to show whether this is really the case."

The average age of the study's participants was 68. Billings said she and her team made sure to adjust for other factors that could affect people's sleep quality, such as body mass, age, smoking or having certain conditions, including sleep apnea or depression.

Air pollution has been linked to the increased risk of respiratory conditions, including asthma and even lung cancer. But recent studies have pointed to the possible association between air pollution and a much wider range of health problems. For example, a study by researchers at the University of Birmingham in the U.K. published earlier this year found that every extra 10 micrograms of PM2.5 per cubic meter of air was linked with a 22 percent increase in risk of dying of any type of cancer in elderly people.

Other research suggests that pregnant women who breathe highly polluted air are more likely to give birth prematurely, according to the Stockholm Environment Institute. A team from the University of Lancaster in the U.K. found air pollution particles in human brains, and said the evidence suggests these particles could contribute to dementia.

Billings and her colleagues presented their new research at the International Conference of the American Thoracic Society earlier this week. The findings have not been published in a peer-reviewed journal.

Originally published on Live Science.

Beer, wine and other alcoholic beverages have somewhat of a split personality in how they affect people's brains. At first, the drinks tend to make people feel super sleepy, but they then jolt those same people wide awake and make them jittery just a few hours later. What's behind this odd effect?

The answer has to do with alcohol's powerful effects on the central nervous system, said A. Leslie Morrow, a professor of psychiatry and pharmacology at the University of North Carolina School of Medicine.

Alcohol enters the bloodstream quickly, usually within about 20 minutes of a person drinking it. It's a small molecule, so once alcohol is in the bloodstream, it can easily cross the blood-brain barrier and affect brain cells, known as neurons, Morrow said. 

Related: Why do we sleep?

In the brain, alcohol targets protein molecules, including GABA-A receptors, which are present on more than 80 percent of all neurons. Normally, these receptors are the destination for GABA (gamma-aminobutyric acid), a neurotransmitter (chemical messenger). Typically, GABA binds to these receptors and opens a channel, letting chloride ions move inside of neurons.

Once chloride ions enter a neuron, they act like light-switch dimmers, slowing down that neuron's firing.

"When you reduce neuronal firing, that causes relaxation, sedation, sleepiness," Morrow told Live Science. If neuronal firing drops too much, it can cause coma and ultimately death, she said.

Alcohol enhances this effect, she explained. That's why when people drink alcohol, they feel more relaxed, more sedated and sleepier than usual. "They might have motor incoordination," Morrow added. "They might forget where they parked their car. They might not be able to concentrate on their homework."

If a person has a high alcohol tolerance, it might take a few more drinks for them to feel this way, Morrow noted. This explains why people with a low tolerance tend to feel these effects, including sleepiness, sooner than people with a higher tolerance.

But why does alcohol also disrupt sleep? Once again, the answer involves GABA-A receptors and neurons. Within about 4 to 5 hours of social drinking (having about three drinks at an event), alcohol molecules in the brain cause GABA-A receptors to loose sensitivity to alcohol and to GABA itself. When this happens, GABA-A receptors move from the surface of the neuron to the inside of the neuron, where they are degraded, Morrow said. This process is called receptor trafficking, she said.

Once GABA-A receptors are inside of the neuron, neither GABA nor alcohol can activate them, Morrow said. Without these keys to let in chloride ions and slow down neuronal firing, the neurons get excited, firing faster than usual, she said.

"That's when we wake up," Morrow said. "This effect depends on dose of alcohol and time after alcohol is consumed. The higher the dose of alcohol, the greater the effect on sleep and waking, since there is both a greater effect on neuronal inhibition and then on receptor trafficking inside the neurons."

Luckily, the body can synthesize new receptors and insert them back on the surface of neurons within a few hours, Morrow said. 

This process happens differently for alcoholics, however, Morrow said.

"They've lost so many GABA receptors that they're not making new ones at the same rate anymore," Morrow said. "If they have fewer receptors, they're likely to be anxious [and] nervous, have dysphoria [a state of feeling unwell], and have trouble sleeping, just in general. That's what drives them to want to drink more. That perpetuates more drinking, and it leads to a vicious cycle."

Morrow noted that alcohol's effects on the brain are much more complicated than described here.

"Since alcohol acts on many proteins, other proteins also contribute to its inhibitory activity in the brain, as well as the excitation that wakes people in the middle of the night," she said. "[But] GABA-A receptors are very sensitive to alcohol, and [they] play a major role in the mystery of alcohol's actions."

If people wake up in the middle of the night after an evening of drinking, they should try relaxation techniques, such as deep breathing, to calm down, Morrow said. This can help keep feelings of mounting anxiety at bay, she said.

"You can obviously rev yourself up and make yourself more excited," Morrow said. "Realize that it's OK to rest. That if you can't sleep, that resting is good enough. Do things to calm yourself down, then your next day probably will be fine."

Originally published on Live Science.

Toddlers are fiddling more with tablets and smartphones during the day, and it's robbing them of sleep at night, a new study from England suggests.

In the study, children ages 6 months to 3 years who spent more time playing with touch-screen devices during the day got less sleep overall and took longer to fall asleep, compared with the youngsters who used touch screens less frequently, the researchers found.

The findings also showed that compared with the kids who used touch screens less frequently, the babies and small children who used touch screens more often slept more during the day but less at night, according to the study, published today (April 13) in the journal Scientific Reports. [7 Ways to Short-Circuit Kids' Mobile Addiction]

This is the first study to look at the link between toddlers' touch-screen use and sleep, said lead study author Tim Smith, a lecturer in cognitive psychology at Birkbeck, University of London.

Although the use of smartphones and tablets is widespread, little was known about the extent to which infants and toddlers were using touch-screen devices in the U.K. before the researchers carried out their study, Smith said. Still, despite a dearth of studies on the subject, parents had been advised to limit their small children's screen time due to concerns about its possible negative effects on sleep, he noted. 

In the new study, the researchers asked more than 700 families in the U.K. to complete an online questionnaire. This survey asked parents how often their youngsters played with a smartphone or tablet on a typical day. The parents also provided information about how much time their child spent sleeping, how often the child woke up each night and how long it took for the child to fall asleep.

Less overall sleep

Previous studies in children and teens have shown that there's a connection between increased screen time and both a later bedtime and less shut-eye each night. But scientists had a limited understanding of the effects of touch-screen use on sleep in young children.

The study found that infants that were 6 to 11 months old used touch screens for about 8 minutes a day, on average. Kids ages 12 to 18 months used them for an average of 19 minutes a day, and kids ages 19 to 25 months used them for 25 minutes a day on average. The 2-year-olds (older than 25 months) in the study logged about 44 minutes a day, on average, on the devices. And as touch-screen time increased among younger children, it cut into their sleep, the researchers found.

Every additional hour of touch-screen use by young children was associated with 15.6 minutes less total sleep, according to the study. Specifically, each additional hour spent using a touch screen was linked to 26 fewer minutes of sleep at night, on average, and 11 more minutes of sleep during the day, on average, for a total of 15 fewer minutes of sleep overall. [25 Scientific Tips for Raising Happy Kids]

The researchers didn't look into why more use of tablets and smartphones interfered with sleep in young children. Other research, however, has suggested some possible ways that more screen time can affect sleep in older children and teens, and these factors may also affect younger children, the researchers noted.

One explanation is that time spent using these devices cuts into the time available for older kids and teens to nod off, Smith told Live Science. In other words, instead of sleeping, adolescents are spending time on smartphones and tablets.

In addition, using touch screens can stimulate a child mentally and physiologically, making it more difficult for them to fall asleep and preventing them from sleeping as well as they otherwise would, Smith said.

Nor did the researchers look at whether the reduced amount of sleep in young children had a negative effect on their health, well-being or development, Smith said. But in future studies, the research team hopes to examine the long-term effects of touch-screen use on children's brains, development and cognitive abilities, he said. [11 Facts Every Parent Should Know About Their Baby's Brain]   

In the meantime, Smith said, the best guidelines for parents on electronic media use in children comes from the American Academy of Pediatrics. The AAP advises limiting a child's overall use of these devices coupled with carefully supervising the activities that children are doing on these devices, he noted.

It's also a good idea for children to avoid using smartphones and tablets in the hour before bedtime, Smith added.

Originally published on Live Science.

People who are in a deep slumber may not be able to say whether they're dreaming, but their brain waves might.

In a new study, scientists say they can predict whether people are dreaming by looking at the brain activity in a region at the back of the brain, which they dub the posterior cortical "hot zone."

"Monitoring this posterior 'hot zone' in real time predicted whether an individual reported dreaming or the absence of dream experiences … suggesting that it may constitute a core correlate of conscious experiences in sleep," the researchers wrote in the study, published online April 10 in the journal Nature Neuroscience. [7 Mind-Bending Facts About Dreams]

For many years, scientists thought that dreaming occurred mostly during a stage of sleep known as rapid eye movement, or "REM," sleep. But more recent studies have found that many people also report dreams when they are woken up during a different stage of sleep called non-REM sleep.

In the new study, the researchers monitored the brain waves of 46 people while they slept, using electroencephalography (EEG), a method of recording the brain's electrical activity. The researchers woke up the participants at different stages of sleep, and asked them whether they were dreaming just before they woke up. The researchers looked for differences in brain waves between the people who said they had just been dreaming versus the people who said they had not.

The researchers found that, when the participants were dreaming, they showed a decrease in low-frequency brain waves, and an increase in high-frequency brain waves, in the posterior hot zone, compared with when they weren't dreaming. They found this pattern regardless of whether the participants were dreaming during REM or non-REM sleep.

Using this brain wave pattern, the researchers found that they could predict whether a person was dreaming during non-REM sleep with about 90 percent accuracy, the report said.

The researchers also found that a person's pattern of brain activity could sometimes reveal a bit about what they had been dreaming about. For example, if there were faces in a person's dream, there was an increase in high-frequency brain waves during REM sleep in an area of the brain typically used to process information on faces.

The researchers said their findings may have implications beyond sleep, for the study of consciousness itself. That's because activity in the "hot zone" was linked with "conscious" experiences during sleep (dreams), as opposed to unconsciousness, or dreamless sleep, they said.

Original article on Live Science.