Australian researchers, reporting in Circulation: Journal of the American Heart Association, studied the lifestyle habits of 8,800 adults. They found that each hour spent watching television on a daily basis is associated with an 18% increased risk of death from cardiovascular disease.
They also say an hour a day spent in front of the tube is associated
• An 11% increased risk of death from all causes
• A 9% increased risk of cancer death
Human Body Needs to Move
The human body evolved to move, not sit still for extended periods of time, says David Dunstan, PhD, lead author of the study and head of the Physical Activity Laboratory at the Baker IDI Heart and Diabetes Institute in Victoria, Australia. So sitting in front of a TV or a computer screen for too long poses serious risks to health, and to life, 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," Dunstan says in a news release. "Technological, social, and economic changes mean that people don't move their muscles as much as they used to -- consequently the levels of energy expenditure as people go about their lives continue to shrink. 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."
Dunstan and his team of researchers looked at 3,846 men and 4,954 women ages 25 and older to find out what happens to people who sit too much. They were asked about their TV viewing habits and were grouped into one of three categories: people who watched less than two hours of TV daily, those who watched between two and four hours of television daily, and those who spent more than four hours in front of the tube. The researchers excluded people with a history of cardiovascular disease, and the entire group was then followed for more than six years. During the study period, 284 of the people died, 125 from cancer and 87 because of cardiovascular disease.
Dunstan and his colleagues write that the link between cancer and TV viewing was only modest, but that there was a direct association between television time and elevated cardiovascular death, as well as death from all causes. This was true, they say, even after accounting for typical cardiovascular disease risk factors and other lifestyle practices.
Avoiding a Sedentary Lifestyle
Dunstan says the implications were simple and clear -- too much TV time can be deadly.
"In addition to doing regular exercise, avoid sitting for prolonged periods and keep in mind to move more [and] more often," Dunstan says. "Too much sitting is bad for health."
He and his co-authors note that previous research has shown that moderate to vigorous exercise reduces premature death. Less has been known, though, about the deadly consequences of sedentary behavior. The evidence, they write, is now clear.
"These novel findings from a large population-based cohort of Australian men and women indicate that prolonged television viewing time is associated with an increased risk of all-cause and [cardiovascular] disease mortality," the researchers write. "Each one-hour increment in television viewing time was found to be associated with an 11% and an 18% increased risk of all-cause and [cardiovascular] disease mortality."
"Furthermore, relative to those watching less television, there was a 46% increased risk of all-cause and an 80% increased risk of [cardiovascular disease] mortality in those watching four [or more] hours of television per day."
That was true even when factoring in other known risks, such as smoking, blood pressure, cholesterol, and diet, the authors say, as well as leisure-time exercise and waist circumference, the study says.
By Bill Hendrick
Reviewed by Elizabeth Klodas
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