Is watching too much TV bad for your health?

By Stephen Beech

Watching less than one hour of television a day slashes the risk of a heart attack or stroke, according to new research.

A couch potato lifestyle - such as watching TV two or more hours daily - may be a "key factor" in the risk of developing heart and blood vessel diseases, say scientists.

Researchers analyzed genetic and lifestyle information as well as the medical records of more than 340,000 British men and women, with an average age of 56.

They found that people with higher genetic risk for Type 2 diabetes (T2D) may be more likely to have a heart attack, stroke or other types of atherosclerotic cardiovascular disease (ASCVD).

But limiting TV watching to no more than one hour a day may help "offset" the increased risk.

The findings showed that people who had high T2D genetic risk but who watched less an hour of TV a day had a relatively lower risk of developing ASCVD within the next 10 years compared with people who had low T2D genetic risk but watched TV for two or more hours every day.

The research team explained that ASCVD is caused by plaque build-up in arterial walls and refers to conditions that include heart disease, stroke and peripheral artery disease.

This study, published in the Journal of the American Heart Association, is one of the first to examine how the genetic risk for diabetes may be linked to TV viewing habits.

Lead author Professor Youngwon Kim, of The University of Hong Kong, said: “Type 2 diabetes and a sedentary lifestyle, including prolonged sitting, are major risk factors for atherosclerotic cardiovascular diseases.

"Watching TV, which accounts for more than half of daily sedentary behavior, is consistently associated with an increased risk of Type 2 diabetes and atherosclerosis.

"Our study provides new insights into the roles of limiting TV viewing time in the prevention of atherosclerotic cardiovascular diseases for everyone and especially in people with a high genetic predisposition for Type 2 diabetes.”

During nearly 14 years of follow-up, researchers identified 21,265 of the 346,916 UK participants who developed ASCVD.

For each participant, researchers calculated a "polygenic risk score" for Type 2 diabetes based on 138 genetic variants associated with the condition.

They explained that a polygenic risk score is a statistical method to predict a person’s risk of developing a particular disease or condition by combining information from genetic variants.

Around 21% of the participants reported watching TV one hour or less a day, while more than 79% reported two or more hours per day of TV-watching time.

The findings showed that spending two hours or more daily in front of the TV was associated with a 12% higher risk of cardiovascular disease compared to watching TV for one hour or less daily, regardless of genetic risk for Type 2 diabetes.

Study first author Dr. Mengyao Wang, also of The University of Hong Kong, said: “We found that people with high genetic risk for Type 2 diabetes may exhibit lower chances of developing atherosclerotic cardiovascular disease by limiting TV watching to one hour or less each day.

"This suggests that less TV viewing could serve as a key behavioral target for preventing atherosclerotic cardiovascular diseases linked to Type 2 diabetes genetics."

She added: “Future strategies and actions to prevent disease and improve health by reducing time in front of the TV and promoting other healthy lifestyle modifications should target broad populations, including those with a high genetic risk for Type 2 diabetes."

The findings were welcomed by the American Heart Association (AHA).

Professor Damon Swift, chair of the AHA’s physical activity committee, said: “This study shows that reducing TV watching can benefit both people at high risk for Type 2 diabetes and those at low risk.

"It also highlights how lifestyle choices can improve health."

Swift, of the University of Virginia, added: “These findings add to the evidence that sitting time may represent a potential intervention tool to improve health in people in general, and specifically for people with a high risk for Type 2 diabetes.

"This is especially important because people with Type 2 diabetes are at a heightened risk for cardiovascular disease compared to those who do not have diabetes.”

He said targeted interventions could help people who sit for long periods of time at home or at their workplaces.