2 Hours a Day Raises Heart, Diabetes Risk
By Salynn Boyles
WebMD Health News
Reviewed by Louise Chang, MD
June 14, 2011 -- The average American spends about 5 hours a day watching TV, which is more time than is devoted to any other activity with the exception of sleeping and working.
Now a new analysis of past studies by researchers from the Harvard School of Public Health helps to quantify the risk.
3 Hours of TV a Day Linked to Early Death
More than two hours of TV watching a day was found to raise the risk for type 2 diabetes and cardiovascular disease, while more than three hours of TV time was associated with an increased risk for early death, Harvard professor of nutrition and epidemiology Frank B. Hu, MD, PhD, tells WebMD.
He says Europeans watch an average of about three hours of television a day.
Compared to three hours of daily watching, the typical American's five hours of TV time was associated with a 20% increase in type 2 diabetes, a 15% increase in risk for cardiovascular disease, and a 13% increased risk for premature death, says Hu.
The study appears in tomorrow's issue of the Journal of the American Medical Association.
"We have known that excessive TV watching is an important risk factor for these diseases and early death," Hu says. "This analysis shows that the relationship is linear and substantial. The more time someone spends watching TV, the greater their risk."
The analysis included eight large studies conducted during the past four decades examining the impact of TV time on diabetes, heart and vascular disease, and early death. Study participants were followed for an average of seven to 10 years.
Based on disease incidence in the United States, the researchers estimated that each additional two hours of TV time results in about 100 early deaths for every 100,000 American adults per year.
TV Watching Promotes Poor Diet
It stands to reason that the more time people spend in front of the TV, the less time they have to engage in more active pursuits linked to better health.
But Hu believes TV watching is more risky than other sedentary behaviors like working at a computer all day because it is associated with poorer eating behaviors.
"People tend to eat while they watch TV, and they tend to eat junk foods and sugary beverages," he says. "This may have something to do with the fact that they are bombarded with commercials for these foods."
Joel Zonszein, MD, who directs the Clinical Diabetes Center at New York's Montefiore Medical Center, says the findings from the newly published analysis are no surprise.
"The more time people spent in front of the TV, the higher their risk for diabetes, cardiovascular disease, and even death," he tells WebMD. "When you see this type of linear response, that is pretty reliable evidence of an association."
But he adds that the study was limited by the fact that the researchers were unable to assess the impact of diet and exercise on risk.
Zonszein and Hu agree that efforts to convince Americans to limit their TV screen time should start with children. Hu says even though no more than two hours of TV a day is recommended (and none for children under age 2), the average child in the U.S. watches four or five hours of TV a day, just like their parents.
"TV watching has been linked to childhood obesity and metabolic syndrome in children," Hu says. "It stands to reason that excess screen time can set them up for poor health and early death as adults."