Lounging in front of the tube not only eats up hours in your day, it may also shorten your life, according to a new study.
The study, which looked at the connection between watching TV and death for 8,800 Australian adults, found that each hour of TV-viewing was associated with an 11 percent increased risk of death from any cause, and an 18 percent increased risk of death from cardiovascular disease. These findings held true even after the researchers took into account other factors that could raise the risk of dying, such as age, gender, waist circumference and exercise habits.
While the study included only Australians, the findings likely apply to Americans, who spend even more time watching TV, the researchers said. The results could also apply to any sedentary activity – yes including sitting in front of a computer all day – not just TV-watching. And skinny people could be victims as well, the researchers say.
The researchers suggest this link between TV-time and early death could be partly due to the fact that sitting in front of the tube may take away from time a person might otherwise spend moving about, engaging in light activity, which has been shown to reduce the risk of developing certain biological indicators of cardiovascular disease. The new results agree with those of another recent study, which showed that adults who watch less TV also burn more calories.
The results also showed that those who watched TV for four hours a day or more had a 46 percent increased risk of death from any cause and an 80 percent increased risk of death from cardiovascular disease, compared with those who watched TV less than two hours a day. This connection was found to be independent of other risk factors for death and cardiovascular disease, including smoking, high cholesterol, poor diet, high blood pressure and a large waistline.
Couch potato society
While several studies have shown how frequent exercise can reduce your risk of dying prematurely, less research has focused on the flip side of the question — whether too much sitting down can shorten your life.
The researchers focused on TV-watching, because it is the main sedentary activity in many developed countries (other than sleeping). In Australia and the United Kingdom, the average person watches about three hours of TV a day, the study’s authors say, while in the United States, the average daily viewing time is around 5 hours, according to a recent report from the Nielsen Company.
Anyone who sits down for a long period of time may be at risk, the researchers say.
"What has happened is that a lot of the normal activities of daily living that involved standing up and moving the muscles in the body have been converted to sitting," David Dunstan, study author and researcher at the Baker IDI Heart and Diabetes Institute in Victoria, Australia, said in a statement.
"Technological, social, and economic changes mean that people don't move their muscles as much as they used to, [and] consequently the levels of energy expenditure as people go about their lives continue to shrink."
Dunstan added, "For many people, on a daily basis they simply shift from one chair to another — from the chair in the car to the chair in the office to the chair in front of the television."
And skinny people are not off the hook when it comes to the risks of sedentary behavior. “Even if someone has a healthy body weight, sitting for long periods of time still has an unhealthy influence on their blood sugar and blood fats," he said.
Tallying TV time
The participants in the study included 3,846 men and 4,954 women over the age of 25 who took part in the Australian Diabetes, Obesity and Lifestyle Study, a national study intended to look at the prevalence of diabetes, cardiovascular disease and kidney disease in the country, and attempt to understand the risk factors for these conditions. The subjects were surveyed about their lifestyle habits, including how much TV they had watched in the past week. They also provided blood samples so researchers could examine their cholesterol and blood sugar levels. The participants were initially enrolled in 1999 and were followed for a period of six years. The researchers excluded those with a history of cardiovascular disease.
A drawback to the study is that it was based on people’s own estimates of how much TV they were watching, which may not be accurate. However, since people would probably rather downplay how much TV they actually watch, the study is more likely to have underestimated the TV-death risk than overestimated it, the researchers say.
The study’s take-away message is rather simple, he said. "In addition to doing regular exercise, avoid sitting for prolonged periods and keep in mind to 'move more, more often.' Too much sitting is bad for health."
The study was published online Jan. 11 in Circulation, a journal of the American Heart Association.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.