Every hour spent watching TV, DVDs and videos as an adult reduces life expectancy¹ by almost 22 minutes, a study suggests. And viewing TV for an average of six hours a day can cut short your life by five years.

一项研究指出，成年人每看一小时电视、DVD或视频就会减少22分钟的寿命。每天平均看6小时电视会减寿5年。

The research claims that a sedentary（久坐的） lifestyle is as bad for health as smoking and obesity², because of the dangers posed by inactivity and the greater opportunities it offers for unhealthy eating.

The academics conducting the study set out to calculate the overall risk to life expectancy from watching television. Their research involved more than 11,000 people over the age of 25.

Writing in the British Journal of Sports Medicine, they concluded: ‘TV viewing time may be associated with a loss of life that is comparable to other major chronic³ disease risk factors such as physical inactivity and obesity.’

The researchers, from the University of Queensland, used information from the Australian Diabetes⁴, Obesity and Lifestyle Study, together with population and death rate data.

But they said: ‘While we used Australian data, the effects in other industrialised and developing countries are likely to be comparable, given the typically large amounts of time spent watching TV and similarities in disease patterns.’ In the UK, the average amount of time spent watching TV is four hours a day compared with five hours in the United States.

Researchers from the Harvard School of Public Health, Boston, said it was ‘biologically plausible（貌似可信的） ' that prolonged TV viewing results in disease and premature⁵ death. Other work suggests that sedentary behaviour is linked to obesity, high levels of bad blood fats and other heart disease risk factors, and more opportunities for grazing on junk foods.

Earlier this year, a separate study suggested the risk of developing type 2 diabetes and heart disease, or dying prematurely⁶, rises by as much as 20 percent after just two hours a day in front of the box.

England’s Chief Medical Officer, Sally Davies, said: ‘Physical activity offers huge benefits and these studies back what we already know – that a sedentary lifestyle carries additional risks. We hope these studies will help more people realise that there are many ways to get exercise.’

Another study shows that exercising for just 15 minutes a day can increase your lifespan by up to three years. It can reduce the risk of early death by 14 percent, with each extra 15 minutes reducing all-cause death rates by 4 percent.