Boston, MA - Confirmation that sitting in front of the television for prolonged lengths of time has long-term adverse effects has come from a new review of studies showing a direct relation between the amount of television viewing and risk of type 2 diabetes, cardiovascular disease, and all-cause mortality.
The review, published in the June 15, 2011 issue of the Journal of the American Medical Association, showed that for every two hours of television watched daily, the risk of diabetes increased by 20%, the risk of cardiovascular disease increased by 15%, and the risk of all-cause mortality increased by 13%.
Coauthor of the study, Dr Frank Hu (Harvard School of Public Health, Boston, MA), commented to heartwire: "TV watching is worse than other sedentary activities in that it is particularly passive. It has a lower energy expenditure compared with driving, reading, working at a computer, etc."Associated with junk food
He also maintains that watching television is associated with unhealthy eating behavior. "People tend to eat when they are watching television, and they also tend to eat junk food and sugary beverages rather than healthier food. This might be related to the large amount of commercials for junk food, which increase the appetite, or it may just be due to boredom. Junk food is more readily available and therefore suitable for eating in front of the television. Perhaps if people were not watching television, they would be more inclined to make themselves a proper healthier meal."
Hu notes that the culture of television watching is a direct result of the technological revolution. "With the availability of satellite television, with hundreds of channels, we are watching more and more TV, and with a remote control we don't even have to get up from the sofa to change channels."
He added: "I'm not advocating a ban on television. But our behavior has become excessive. The average American watches five hours of TV every day. That is too much. And people get into a vicious circle. They watch a lot of TV, so start to put on weight, and that makes it more difficult to exercise, so they watch more TV. . . . I think we need to be telling people that they can cut their risks of diabetes and heart disease by reducing their time watching TV."Exercise while watching TV
"Public-health messages recommend an increase in physical activity, but they don't actually stipulate less television watching. That is something that is not too difficult to change. We should also be suggesting that people do some exercise while watching television. We could develop technology to enable people to expend more energy when watching TV, like using a treadmill or other exercise equipment."
In the paper, Hu and his coauthor, Anders Grøntved (University of Southern Denmark, Odense), report that television watching is the most commonly reported daily activity apart from working and sleeping in many populations around the world, with an average of 40% of daily free time occupied by TV viewing within several European countries and 50% in Australia.
They performed a meta-analysis of eight prospective cohort studies looking at the association between TV viewing and risk of type 2 diabetes, fatal or nonfatal cardiovascular disease, and all-cause mortality. Results showed pooled relative risks per two hours of TV viewing per day of 1.20 for type 2 diabetes, 1.15 for fatal or nonfatal cardiovascular disease, and 1.13 for all-cause mortality.
The estimated absolute risk differences per every two hours of TV viewing per day were 176 cases of type 2 diabetes, 38 cases of fatal cardiovascular disease, and 104 deaths from any cause per 100 000 individuals per year.
By Sue Hughes of theheart.org, June 14, 2011
Sue graduated in pharmacy from Manchester University, UK and worked as a hospital pharmacist before moving on to health journalism.
Grontved A, Hu FB. Television Viewing and Risk of Type 2 Diabetes, Cardiovascular Disease, and All-Cause Mortality, A Meta-analysis. JAMA. 2011;305(23):2448-2455.