Australian researchers at the Baker IDI Heart and Diabetes Institute in Victoria have found that the risk of heart disease increases by one-fifth for every hour spent watching TV daily.

The seven-year study followed the TV viewing habits of 8,800 people and found that those who spent four hours or more per day watching television had an 80 per cent increased risk of developing heart disease, compared with those who watched TV for less than two hours a day. Those who spent regular amounts of time in sedentary activities such as sitting at their computer or driving also faced increased risk.

The researchers say that all sedentary activities carry added risks of disease, including cancer.

Lead researcher Prof David Dunstan said:

‘Even if someone has a healthy body weight, sitting for long periods of time still has an unhealthy influence on their body sugar and blood fats.’

The team said that, during the six-year follow-up from the study, 87 participants died from diseases related to heart conditions – and a further 125 died from cancer.

In the UK, people watch TV for an average of three hours per day. Senior Cardiac Nurse at the British Heart Foundation, Fotini Rozakeas, said that further research was needed, however, to calculate the risk:

‘Although this study suggests a strong association between watching TV and dying of heart and circulatory disease, it is not clear why. The study was observational and previous research has not suggested such a dramatic link.

‘The researchers had allowed for the poor dietary habits associated with watching a lot of TV – like eating unhealthy snacks and also smoking – so it is not clear cut why people were considered to be so at risk of death and disease.

‘It raises questions such as, if you are physically active and not overweight, are you still at risk if you watch a lot of TV? And how much is too much?’

The study is published in the journal Circulation: Journal of the American Heart Association.

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