Reducing TV time may lower heart disease risk, even for those genetically prone to diabetes

Limiting daily television viewing to one hour or less may help reduce the risk of heart attack, stroke, and other cardiovascular diseases, even in individuals with a high genetic predisposition to Type 2 diabetes, according to new research.

The study, published Wednesday in the Journal of the American Heart Association, is among the first to explore how genetic susceptibility to Type 2 diabetes interacts with TV-watching habits in relation to atherosclerotic cardiovascular disease (ASCVD), a condition caused by plaque buildup in the arteries.

"Type 2 diabetes and sedentary behaviors, including prolonged sitting, are key risk factors for ASCVD," said lead author Dr. Youngwon Kim, a professor at the University of Hong Kong's School of Public Health.

"Since TV viewing makes up a significant portion of daily inactivity, it has been consistently linked to a higher risk of Type 2 diabetes and atherosclerosis," Kim noted. "Our study highlights the potential role of reducing TV time in preventing ASCVD, particularly in those with a strong genetic predisposition for diabetes."

ASCVD encompasses heart disease, stroke, and peripheral artery disease, leading to complications such as reduced quality of life, arterial procedures, amputations, and premature death.

Researchers analyzed genetic, lifestyle, and medical data from 346,916 adults in a large UK-based biomedical database. The participants, with an average age of 56, were monitored for nearly 14 years. During this period, 21,265 individuals developed ASCVD.

To assess genetic risk, researchers calculated polygenic risk scores—an assessment combining 138 genetic variants linked to Type 2 diabetes. Participants were categorized as having a low, medium, or high genetic risk for the condition. Their TV habits were also self-reported, dividing them into groups watching one hour or less daily and those watching two or more hours.

Only 21% of participants limited their TV time to one hour or less. Those watching two or more hours daily faced a 12% higher risk of developing ASCVD, regardless of their genetic risk for diabetes. However, individuals with medium or high genetic risk did not show an increased likelihood of developing ASCVD if they restricted their TV time to one hour or less per day.

Interestingly, people with a low genetic risk for diabetes who watched at least two hours of TV daily had a slightly higher 10-year ASCVD risk (2.46%) compared to those with a high genetic risk who limited their TV time (2.13%).

"This suggests that reducing TV time could be a key behavioral strategy for preventing ASCVD in those with a genetic predisposition to Type 2 diabetes," said study co-author Dr. Mengyao Wang of The University of Hong Kong. Wang emphasized that encouraging people—especially those at high genetic risk—to minimize TV time and adopt healthier habits could significantly improve heart health.

Dr. Damon L. Swift, an associate professor at the University of Virginia's department of kinesiology, who was not involved in the study, supported these findings.

"This research underscores the impact of lifestyle choices on health," Swift said. "It adds to growing evidence that reducing sedentary behavior, such as TV viewing, can be an effective intervention for improving cardiovascular health—particularly for those at an elevated risk of Type 2 diabetes, who already face a higher likelihood of developing heart disease."