Prolonged television viewing linked to increased health risks

Watching television is the most common daily activity apart from work and sleep in many parts of the world, but it is time for people to change their viewing habits. According to a new study from Harvard School of Public Health (HSPH) researchers, prolonged TV viewing was associated with increased risk of type 2 diabetes, cardiovascular disease, and premature death.

The study appears in the June 15, 2011, edition of the Journal of the American Medical Association.

“The message is simple. Cutting back on TV watching can significantly reduce risk of type 2 diabetes, heart disease, and premature mortality,” said senior author Frank Hu, professor of nutrition and epidemiology at HSPH. “We should not only promote increasing physical activity levels but also reduce sedentary behaviors, especially prolonged TV watching,” said Hu.

Many people around the world divide their days largely between working, sleeping, and watching television, according to the researchers. Europeans spend an average of 40 percent of their daily free time in front of the television set; Australians, 50 percent. This corresponds to three to four hours of daily viewing — still less than a reported average of five hours in the U.S. The negative health effects of TV viewing have been documented in prior studies, including associations with reduced physical activity levels and unhealthy diets.

Hu and first author Anders Grøntved, a doctoral student and visiting researcher in the HSPH Department of Nutrition, conducted a meta-analysis, a systematic assessment of all published studies from 1970 to 2011 that linked TV viewing with increased risk of type 2 diabetes, cardiovascular disease, and premature death. Eight large prospective cohort studies from the United States, Europe, and Australia met the researchers’ criteria and were included in the meta-analysis.