Watching Less TV May Lower Heart Disease Risk, Even in Those Genetically Prone to Diabetes: Study

New Delhi: Watching no more than one hour of TV a day may lower the risk of heart attack, stroke, and other blood vessel diseases among people with varying levels of genetic risk for Type 2 diabetes, including high genetic risk, according to new research published today in the Journal of the American Heart Association.

A sedentary 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, according to an analysis of health records from a large U.K. biomedical database.

People with higher genetic risk for Type 2 diabetes may be more likely to have a heart attack, stroke, or other types of atherosclerotic cardiovascular disease. However, limiting TV watching to no more than one hour a day may help offset the increased risk of these atherosclerotic events associated with a high genetic risk of Type 2 diabetes.

The study examined data from 346,916 adults in the UK Biobank, with an average age of 56 years and 45% male participants.

During a nearly 14-year follow-up period, 21,265 individuals developed atherosclerotic cardiovascular disease, which includes conditions such as heart disease, stroke, and peripheral artery disease caused by plaque buildup in the arteries. These conditions may lead to severe complications such as bypass surgeries, stenting procedures, amputations, and premature death.

For each participant, researchers calculated a polygenic risk score for Type 2 diabetes based on 138 genetic variants associated with the condition. This polygenic risk score is a statistical method used to predict a person’s risk of developing a disease by analysing multiple genetic variants.

Participants were categorized into three groups of Type 2 diabetes genetic risk: low, medium, and high. They also reported their TV viewing time, which was classified into two groups: watching TV for one hour or less daily or two hours or more daily.

The findings showed that about 21% of participants reported watching TV for one hour or less per day, while more than 79% watched two or more hours daily.

Compared to those who watched TV for one hour or less daily, spending two or more hours in front of the TV was associated with a 12% higher risk of atherosclerotic cardiovascular disease, regardless of their genetic risk for Type 2 diabetes.

Evaluations indicated that participants with medium and high genetic risk for Type 2 diabetes did not have a higher risk of developing atherosclerotic cardiovascular disease as long as TV viewing was limited to one hour or less daily.

The 10-year absolute risk of developing atherosclerotic cardiovascular disease was 2.13% for people with high Type 2 diabetes genetic risk who watched TV for one hour or less per day, compared to 2.46% for people with low genetic risk who watched two or more hours daily.

"Type 2 diabetes and a sedentary lifestyle, including prolonged sitting, are major risk factors for atherosclerotic cardiovascular diseases," said Youngwon Kim, Ph.D., lead author of the study and a professor in the School of Public Health at The University of Hong Kong in Pokfulam, Hong Kong. "Watching TV, which accounts for more than half of daily sedentary behaviour, 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."

Mengyao Wang, Ph.D., first author of the study and a recent Ph.D. graduate of The University of Hong Kong, emphasized the significance of the findings.

"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 behavioural target for preventing atherosclerotic cardiovascular diseases linked to Type 2 diabetes genetics," Wang said. "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."

Damon L. Swift, Ph.D., FAHA, chair of the American Heart Association’s Physical Activity Committee and an associate professor at the University of Virginia in Charlottesville, noted the broader implications of the study.

"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," said Swift, who was not involved in this study.

"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 also pointed out that targeted interventions could help people who sit for long periods at home or at work.

The study had some limitations. TV viewing time was self-reported, which may introduce recall bias. Additionally, the study population was primarily white British adults, which means the findings may not apply to other ethnic groups.

The researchers also did not examine whether Type 2 diabetes itself played a direct role in the relationship between TV viewing and cardiovascular disease risk.

Despite these limitations, the study provides important insights into how a simple lifestyle change like reducing TV time could have a significant impact on heart health, especially for those with a genetic risk for Type 2 diabetes.

The findings suggest that limiting sedentary behaviours such as prolonged TV viewing could be a crucial step in preventing cardiovascular disease.