Dialling down television to an hour a day may cut heart disease

Time spent watching TV more of a health risk than use of computer screens, Cambridge study finds

WATCHING less than an hour of television a day could prevent 250,000 cases of heart disease a year, and potentially save 7,000 lives, new research suggests.

Experts at Cambridge University estimate that about one in 10 cases of coronary heart disease could be averted if Britons cut their viewing time.

Coronary heart disease is one of the UK’S leading causes of death, with about 64,000 deaths each year, and sitting for long periods is a known risk factor.

To examine the link between time spent in screen-based sedentary activity researchers examined data from the UK Biobank, a database which records genetic, lifestyle and health information from more than 500,000 people.

They found that people who watched more than four hours of television each day were at greatest risk, regardless of whether they were more genetically susceptible to heart problems.

In contrast, those who watched two to three hours had a six per cent lower risk of developing heart disease than the longest viewers, while people who watched less than an hour had a 16 per cent reduced risk of a diagnosis.

The team said, assuming the link was causal, that 11 per cent of coronary heart disease cases could be prevented if the nation switched to less than an hour of television.

“Our study provides insights into the [role] that limiting TV viewing might have in preventing coronary heart disease,” said Dr Youngwon Kim, a visiting researcher at the MRC Epidemiology Unit, at Cambridge, and assistant professor at the University of Hong Kong.

“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 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.”

However, the study found no link between heart disease and the amount of time sedentary at a computer screen.

Researchers said the reason that television is more dangerous could be that people often sit down to watch television after a high-calorie evening meal, leading to higher levels of glucose and lipids, such as cholesterol, in the blood.

People also often snack more when watching television compared to when surfing the web, and TV viewing tends to be prolonged, whereas individuals using their computer may be more likely to break up their activity.

Dr Katrien Wijndaele, from the MRC Epidemiology Unit, added: “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 Organisation 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,” Dr Wijndaele said.

The research was published in the journal BMC Medicine.