Limiting your TV viewing to less than one hour per day could significantly reduce your coronary heart disease risk, with new research suggesting this could prevent 11% of cases.
A study performed by the Medical Research Council (MRC) Epidemiology Unit, the University of Cambridge and the University of Hong Kong identified that watching too much TV is linked to an elevated coronary heart disease risk, regardless of a person’s genetics. The investigation discovered that one in ten cases of the disease could be averted if people watched less than one hour of TV each day.
The study, funded by the Li Ka Shing Faculty of Medicine at the University of Hong Kong, is published in BMC Medicine.
Coronary heart disease – a leading cause of death
Research from the British Heart Foundation estimates that coronary heart disease causes 64,000 deaths annually in the UK, making it one of the leading drivers of mortality. Moreover, one in eight men and one in 15 women in the UK die from coronary heart disease, and people with the condition are twice as likely to experience a stroke.
Sedentary behaviour – characterised as sitting for long periods instead of being active – is one of the primary risk factors for coronary heart disease. To investigate the effects of sedentary behaviour, the researchers employed findings from the UK Biobank study, which includes data from over 500,000 adults who have been followed prospectively for around 12 years.
The data enabled the team to analyse the relationship between screen-based sedentary behaviour, such as watching TV and using a computer, and an individual’s DNA and coronary heart disease risk. The researchers developed a polygenic risk score – a person’s genetic risk of developing coronary heart disease based on 300 genetic variants known to increase the chances of the condition – for each individual. Higher polygenic risk scores are associated with an increased coronary heart disease risk.
Health implications of indulging in too much TV
The analysis demonstrated that people at the highest coronary heart disease risk were those that who watched more than four hours of TV per day. People who watched two to three hours of TV per day had a 6% lower risk of developing the condition, while those who viewed less than one hour had a 16% lower chance. The association were independent of genetic susceptibility and other risk factors. In contrast, using a computer was now found to influence disease risk.
Dr Youngwon Kim, assistant professor at the University of Hong Kong and the study’s corresponding author, commented: “Our study provides unique insights into the potential role that limiting TV viewing might have in preventing coronary heart disease. Individuals who watch TV for less than one hour a day are 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, a lifestyle change that could help individuals with a high genetic predisposition to coronary heart disease in particular to manage their risk.”
Dr Katrien Wijndaele from the MRC Epidemiology Unit, the last author of the study, said: “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.
“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 and watching TV increases your risk of coronary heart disease because of various potential confounding factors and measurement errors, 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.”
Why does watching TV increase coronary heart disease risk?
The researchers explained that there is an array of reasons why watching TV increases coronary heart disease risk, but using a computer does not. The primary one is that people tend to watch TV following evening dinner, which is usually the highest daily meal in calories, resulting in more elevated glucose and lipid levels in the blood, such as cholesterol. People are also more likely to eat snacks while watching TV than when using a computer, and TV viewing is usually prolonged, whereas people are more likely to take breaks when surfing the web.