Beware, couch time is shortening your life! For every hour of TV viewing, your risk of dying early from heart disease rises by 18 per cent, says a new comprehensive study of sedentary lifestyle.

The study by Australian researchers shows that each hour of TV viewing also increases your risk of dying from cancer by nine per cent.

Overall, each hour spent in front of TV increases your risk of death by 11 per cent.

Not only watching TV, but also doing sedentary jobs — sitting at the desk or in front of a computer — is equally dangerous for your health, according to the study.

As part of their study, the Australian researchers chose 8,800 people — 3,846 men and 4,954 women above 25 years of age — with no cardiovascular problems.

They grouped them into three categories on the basis of their television—viewing habits — those who watched TV less than two hours a day, those who watched it between two and four hours, and those who watched more than four hours.

During the next six years, 284 of them died — 87 from cardiovascular disease and 125 from cancer.

The researchers found that there was modest link between cancer deaths and television viewing. But the link between the time spent watching television and cardiovascular deaths was very direct and strong.

Overall, they found, there was a strong link with death from all sedentary causes, regardless of other lifestyle factors such as smoking, high blood pressure, high blood cholesterol and obesity.

According to study author David Dunstan, who heads the Physical Activity Laboratory at the Baker IDI Heart and Diabetes Institute in Victoria, (Australia), the human body is designed for activity, not for long periods of sitting.

“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,” he said.

The study has been published in Circulation, a journal of the American Heart Association.