Every hour spent watching television shortens the viewer’s life by 22 minutes, academics warn.
Anyone who spends six hours a day in front of the box is at risk of dying five years sooner than those who enjoy more active pastimes, it is claimed.
Researchers say that watching too much TV is as dangerous as smoking or being overweight, and that the “ubiquitous sedentary behaviour” should be seen as a “public health problem”.
Experts from the University of Queensland, Australia, write: “TV viewing time may have adverse health consequences that rival those of lack of physical activity, obesity and smoking; every single hour of TV viewed may shorten life by as much as 22 minutes.”
Referring to Australian and American guidelines that suggest children should spend no more than two hours a day in front of a screen, the academics conclude: “With further corroborative evidence, a public health case could be made that adults also need to limit the time spent watching TV.”
Although health campaigners – and parents – have long warned of the dangers of watching too much television, its effects on life expectancy have never before been calculated.
In a paper published in the British Journal of Sports Medicine, Dr J Lennert Veerman and colleagues looked at the results of a survey of 11,247 Australians taken in 1999-2000, which asked about time spent watching TV, and also mortality figures for the country.
They constructed a model in which they compared life expectancy for adults who watch TV to those who did not, and worked out that every hour spent glued to the screen shortened life by 21.8 minutes.
For those in the top 1 per cent of the population who watch six hours of programmes a day, they “can expect to live 4.8 years less than a person who does not watch TV”.
The researchers say that watching TV is among the most common forms of sedentary behaviour, along with sitting in cars.
“Because TV viewing is a ubiquitous behaviour that occupies significant portions of adults’ leisure time, its effects are significant for overall population health.”
England’s Chief Medical Officer, Sally Davies, said: “Physical activity offers huge benefits and these studies back what we already know – that doing a little bit of physical activity each day brings health benefits and a sedentary lifestyle carries additional risks.
“That’s why the UK’s Chief Medical Officers recently updated their advice on physical activity to be more flexible, right from babyhood to adult life.
“Adults, for example, can get their 150 minutes of activity a week in sessions of 10 minutes or more and for the first time we have provided guidelines on reducing sedentary time.