5 Ways the Time Change May Affect Your Health

The rise of the sun is seen at a 2,300-year-old structure in Peru during the June solstice in 2003.
The rise of the sun is seen at a 2,300-year-old structure in Peru during the June solstice in 2003. (Image credit: Ivan Ghezzi)

The annual leap forward that will happen this Sunday (March 13) at 2 a.m. provides an opportunity for researchers to see what the time shift — and the sleep loss that may accompany it — may do to our health.

But while researchers have looked at a number of health trends surrounding the first day of daylight saving time -- including apparent upticks in accidents, heart attacks and suicides --­­ it’s unclear whether the adjusted clock setting is itself responsible for these health issues.

“It’s not really understood why some of these health problems that are published coincide with the time change,” said Russell Rosenberg, vice chairman of the National Sleep Foundation. “We don’t have studies that show the time change actually causes these problems.”

With that in mind, here are five health issues that studies have connected with the loss of an hour that day.

Traffic accidents

An increase in traffic accidents is perhaps the best studied health consequence of the time shift -— even if those studies have yielded conflicting results.

“Sleep loss puts people at much higher risk for motor vehicle accidents,” said Rosenberg.

A 1996 study published in the New England Journal of Medicine showed an 8 percent increase in motor vehicle accidents on the Monday following the time change. A 2001 study from Johns Hopkins and Stanford universities also showed an increase on the Monday following the change.

But those findings have not been universal – a Finnish study published last year did not find a similar increase there.

While the time shift may present a problem, it also may provide a benefit: The extra hour of evening daylight in the spring may help prevent pedestrian fatalities. A 2005 study from the University of Newcastle in England indicated this was the case.

At least one U.S. agency has taken the thought to heart. Last November, as the clock shifted back to daylight standard time, the National Highway Traffic Safety Administration warned drivers that, with nightfall occurring earlier in the evening, “adjusting to the new, low-light environment can take time, and that driving while distracted puts everyone — and especially pedestrians — at greater risk of death or injury.”

Workplace accidents

Workplace accidents may be another side effect of the sleep loss from the one-hour time change. They increase in frequency that Monday.

“Perhaps even more scary is the spike in injury severity,” said Christopher Barnes, an assistant professor at the U.S. Military Academy at West Point. “Instead of bruising a hand, maybe you crush a hand.”

A study Barnes led in 2009 looked at the severity of workplace accidents in miners on the Monday following the time change. The researchers found a 5.7 percent increase in injuries and a 67.6 percent increase in work days lost to injuries. Barnes said the results were likely to be similar in other workplaces with similar hazards.

Sleep loss determines the difference between the relatively common near-miss that happens in mining, and a true accident, said Barnes.

“We’re closer to disaster than we realize,” he said. “The margin for error is not very big.”

“If I were in that environment, one thing I would try to do is get to bed earlier that Saturday night, when the change actually happens,” Barnes said. Also, he suggested, “Try to schedule your most dangerous tasks for other days.”

Sleep loss

In a culture where we are constantly being told we need more sleep, the start of daylight saving time piles another hour per person onto the national sleep debt.

“We’re already a highly sleep-deprived society,” Rosenberg said. “We can ill afford to lose one more hour of sleep.”

Additionally, the shift in the period of daylight can present a challenge in catching up on sleep.

“It does take a little extra time to adjust to this time change, because you don’t have the morning light telling your brain it’s time to wake up,” he said.

Taking a nap on Sunday, Rosenberg said, might help make up some of the deficit.

Heart attacks

The connection between sleep and heart attacks gained attention following a 2008 Swedish study that showed an increase of about 5 percent in heart attacks on the three weekdays following the spring time shift.

As for the reasons, “no one really knows,” said Dr. Imre Janszky, of the Karolinska Institute in Sweden, who conducted the study. “Sleep and disruption of chronobiological rhythms might be behind the observation.”

Heart attacks have been found to be highest on Mondays, so a shift in sleeping patterns may explain that as well, Janszky told MyHealthNewsDaily.

However, there have not been follow-up studies to solidify a connection between heart attacks and the change to daylight saving time.

For those worried about heart attacks, “gradual adaptation for [the time] shift might work,” Janszky said.


Suicide is occasionally connected to the shift to daylight saving time, in part because of a recent study showing an increase in men (but not women) after the time change.

The 2008 Australian study found an increase in suicides among men following the start of daylight saving time -- an increase of roughly 0.44 per day.

The researchers suggested the clock shift leaves many without morning sunlight, which perhaps promotes winter depression, and that depression might lead to suicide.

However, a link between the start of daylight saving time and suicides is far from established.

A better-established finding is that spring is the peak time of the year for suicides.

Safeguarding your home

Each year around this time, many public health officials advise you to remember, while you're changing your clocks, to check your smoke detector and carbon monoxide detector batteries.

You should, but you may have noticed that a six-month check doesn’t really line up with daylight saving anymore. It will be 7½ months before you set your clock back an hour again, thanks to a 2007 law.

The smoke and carbon monoxide detector check at daylight saving is outdated, Amy Rowland, spokeswoman for the CDC Injury Center, told MyHealthNewsDaily. In fact, you should check your smoke detector monthly, Rowland said  – that’s eight times before you “fall back” in November.

Follow MyHealthNewsDaily on Twitter @MyHealth_MHND.

This article was provided by MyHealthNewsDaily, a sister site to LiveScience.

Joe Brownstein
Joe Brownstein is a contributing writer to Live Science, where he covers medicine, biology and technology topics. He has a Master of Science and Medical Journalism from Boston University and a Bachelor of Arts in creative writing and natural sciences from Johns Hopkins University.