A team of scientists from the Medical Research Council (MRC) Epidemiology Unit, the University of Cambridge and the University of Hong Kong say that watching too much TV increases the risk of coronary heart disease, regardless of a person’s genetic makeup.
In a study published today in BMC MedicineThe researchers showed that – assuming a causal link – 11% of cases of coronary heart disease could be prevented if people watched less than an hour of TV each day.
According to the British Heart Foundation, coronary heart disease is one of the leading causes of death in the UK, accounting for around 64,000 deaths each year. In the UK, one in eight men and one in 15 women die from the disease. People with coronary heart disease are twice as likely to have a stroke.
One of the major risk factors for coronary heart disease is sedentary behavior — in other words, prolonged sitting rather than being physically active. To examine the link between screen-based sedentary behaviors such as watching TV and computer use at leisure, a person’s DNA, and their risk of coronary heart disease, researchers examined data from the UK Biobank, a study in which Includes more than 500,000 adults who have been followed prospectively for approximately 12 years.
The team created a polygenic risk score for each person—that is, their genetic risk of developing coronary heart disease—based on 300 genetic variants known to affect their chances of developing it. As expected, individuals with high polygenic risk scores were at greatest risk of developing the condition.
People who watch more than four hours of TV per day, regardless of their polygenic risk score, have the greatest risk of disease. Compared with these individuals, those who watched TV for two to three hours a day had a 6% lower rate of developing the condition, compared with a 16% lower rate than those who watched less than an hour of TV. These associations were independent of genetic susceptibility and other known risk factors.
Leisure time spent using a computer does not appear to affect disease risk.
“Our study provides unique insight into the potential role that limiting TV viewing may play in preventing coronary heart disease,” said Dr. Youngwon Kim, assistant professor at the University of Hong Kong and researcher in the MRC Epidemiology Unit, corresponding author of the study. . , “People who watched TV for less than an hour a day were less likely to develop the condition, independent of their genetic risk.
“Limiting the amount of time you sit watching TV may be a useful, and relatively light touch, lifestyle change that can help individuals with a high genetic predisposition to coronary heart disease manage their risk, especially ”
Dr Caitarian Wijndael from the MRC Epidemiology Unit, the final author of the study, said: “Coronary heart disease is one of the leading causes of premature death, so there are ways to help people manage their risk through lifestyle modifications. Searching is important.
“The World Health Organization recommends reducing the amount of sedentary behavior and replacing it with physical activity of any intensity as a way to stay healthy. Although it is not possible to say with certainty that watching TV will increase your risk of coronary heart disease.” Because of the increased risk of disease, various potential confounding factors and measurement error, our work supports WHO guidelines. It targets this for the general population as well as individuals at high genetic risk of coronary heart disease. suggests a direct, measurable way of achieving that.”
There are a number of possible reasons that could explain the link between TV viewing and coronary heart disease risk, the team says — and specifically, why no link was found with computer use. There is a tendency to watch TV in the evening after dinner, usually our most caloric meal, which leads to high levels of glucose and lipids, such as cholesterol, in the blood. For example, people often snack more while watching TV than surfing the web. Finally, TV viewing tends to last longer, while individuals using their computers may be more likely to sabotage their activity.
The research was funded by the Li Ka Shing Faculty of Medicine at the University of Hong Kong.