EVERY hour spent watching TV each day increases the risk of dying from heart disease by nearly a fifth, say scientists.

Couch potatoes were warned that their lifestyle also increased the risk of death from other causes including cancer.

People who spent hours watching television greatly heightened the chances of dying early from heart attacks and strokes, they found.

Compared with those watching less than two hours of TV, people who sat in front of the box for more than four hours a day were 80 per cent more likely to die for reasons linked to heart and artery disease.

Researchers in Australia monitored 8,800 adults for six years to see what impact watching TV had on their long-term health.

They found that each hour spent per day in front of the television increased the risk of death from all causes by 11 per cent.

It also raised the risk of dying from cancer by nine per cent and the risk of heart disease- related death by 18 per cent.

The scientists warned that it was not only telly addicts whose lazy lifestyles put them in danger. Any prolonged sedentary behaviour, such as sitting at an office desk or in front of a computer, posed similar risks, they said.

It also made no difference whether or not a person was overweight or obese.

“Even if someone has a healthy body weight, sitting for long periods of time still has an unhealthy influence on their blood sugar and blood fats,” said Professor David Dunstan, from the Baker IDI Heart and Diabetes Institute in Victoria, Australia.

The average amount of TV people watch each day is three hours in Australia and the UK, said the scientists.

In the US, where two-thirds of adults are overweight or obese, some people spent as much as eight hours watching television.

“What has happened is that a lot of the normal activities of daily living that involved standing up and moving the muscles in the body have been converted to sitting,” said Prof Dunstan.

“Technological, social, and economic changes mean that people don’t move their muscles as much as they used to.

“Consequently, the levels of energy expenditure as people go about their lives continue to shrink. For many people, on a daily basis they simply shift from one chair to another – from the chair in the car to the chair in the office to the chair in front of the television.”