More than one in 10 cases of coronary heart disease could be prevented if people reduced their TV viewing to less than an hour a day.

The narrowing of the coronary arteries causes the heart's blood supply to be reduced. The risk of developing the disease could be lowered by cutting down on time spent in front of the TV.

Reducing time spent watching TV should be recognised as a key behavioural target for prevention of coronary heart disease, regardless of genetic susceptibility and traditional risk markers, said Dr Youngwon Kim, an assistant professor at the University of Hong Kong.

Kim said previous studies had found excessive TV viewing time is associated with adverse levels of cholesterol and glucose in the body.

Unfavourable levels of these cardiometabolic risk markers may lead to increased risk of developing coronary heart disease.

Kim and colleagues used data from over 350,000 white British people who were part of the UK Biobank study.

None of the participants in the team's study had cardiovascular disease when they were recruited to the UK Biobank. The researchers found 9,185 cases of the disease in participants through national death registry and hospital admission records.

The study suggests that after taking into account the genetic risk of coronary heart disease, calculated for each participant, as well as factors including body mass index, age, sex, smoking status, diet, amount of physical activity and level of deprivation, the greater.

Compared with people who watched four or more hours of TV a day, those who watched an hour or less had a 16% lower risk of developing coronary heart disease, while those who watched two to three hours a day had a 6% lower risk.

The researchers say the trend held across all ages and levels of genetic risk, although those with a higher genetic risk of coronary heart disease had a greater risk of developing the condition.

There was no link between the amount of leisure-time computer use and the risk of coronary heart disease due to factors such as greater reliability in recalling TV viewing, snacking while watching TV, or TV watching tending to be more prolong and uninterrupted.

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The link between TV watching and coronary heart disease risk cannot be proved, but the team estimates about a tenth of coronary heart disease cases could be prevented if people cut their TV watching to less than an hour a day.

The findings may underestimate the benefits of cutting TV time on heart disease risks, according to a professor at the University of Glasgow who was not involved in the work.

Increasing activity time by replacing time spent sitting helps lower body fat levels and prevents weight gain, improves blood pressure and blood fat levels, and lowers diabetes risks. All such improvements are known to reduce heart attack and stroke risks.