Watching TV for long periods can increase the risk of cardiovascular disease independent of the patient’s genetic makeup, according to a study published in the journal BMC Medicine. The researchers from the Medical Research Council (MRC) Epidemiology Unit, the University of Cambridge, and the University of Hong Kong say that about 10% of cases of coronary heart disease could be prevented if patients started watching less than one hour of TV each day.
Coronary heart disease is one of the UK’s leading causes of death, with over 60,000 patients dying every year. In the UK, about one in eight men and one in 15 women die from this disease. “Coronary heart disease is one of the most prominent causes of premature death, so finding ways to help people manage their risk through lifestyle modification is important,” said Dr. Katrien Wijndaele from the MRC Epidemiology Unit.
Researchers know that one of the main risk factors for heart disease is sitting for long periods during the day and not being physically active. To assess the link between time spent sitting down watching TV or playing on the computer and the risk of heart disease, the team from Cambridge examined data from the UK Biobank, with over 500,000 adults who have been followed up for about 12 years.
To see how genetics can impact, the researchers calculated a risk score for each person, representing their genetic risk of developing heart disease based on 300 genes known to influence this condition. Not surprisingly, patients with higher genetic scores were at higher risk of developing heart problems. However, people who watched more than four hours a day were also at increased risk, regardless of their genetic risk score. People who watched less than one hour a day were much less likely to suffer heart problems.
“Our study provides unique insights into the potential role that limiting TV viewing might have in preventing coronary heart disease,” said Dr. Youngwon Kim, assistant professor at the University of Hong Kong and visiting researcher at the MRC Epidemiology Unit. “Individuals who watch TV for less than one hour a day were less likely to develop the condition, independent of their genetic risk. Limiting the amount of time sat watching TV could be a useful, and relatively light touch, lifestyle change that could help individuals with a high genetic predisposition to coronary heart disease in particular to manage their risk.”
Curiously, playing on the computer didn’t have the same effect. The authors speculate why this may happen: for most people, watching TV happens in the evening after their main meal. This can be a high calorific meal leading to elevated glucose and lipid levels in the blood. People also snack more while watching TV for long periods compared to playing video games, where people are more likely to break up their activity.
“The World Health Organization recommends reducing the amount of sedentary behaviour and replacing it with physical activity of any intensity as a way of keeping healthier. While it isn’t possible to say for certain that sitting watching TV increases your risk of coronary heart disease because of various potential confounding factors and measurement error, our work supports the WHO’s guidelines. It suggests a straightforward, measurable way of achieving this goal for the general population as well as individuals at high genetic risk of coronary heart disease,” concluded Dr. Wijndaele.
Kim, Y, et al (2022) Genetic susceptibility, screen-based sedentary activities and incidence of coronary heart disease. BMC Medicine; DOI: 10.1186/s12916-022-02380-7