WATCHING television for less than three hours a day increases your life by two years, experts say. Reducing it by another hour – to less than two hours daily – extends lifespan by almost 1.4 years extra, they believe.
It is believed sitting down to watch TV for too long has a negative impact on the health of men and women of all ages.
Doctors say the findings show the need for people to become more active and less likely to become couch potatoes.
Previous studies have linked extended periods of time spent sitting down watching TV to poor health and increased risk of suffering from diabetes, heart disease and stroke. Researchers looked at the lifestyles and health of 167,000 people across the United States for the study.
They compared lifestyles of men and women over a five-year period to determine how inactivity impacted on their health.
Experts used the figures to create a population attributable fraction (PAF) – an estimate of the theoretical effects of a risk factor at a population, rather than an individual level – to calculate the number of deaths associated with time spent sitting.
The team found the PAFs for deaths from all causes linked to sitting time and TV viewing were 27 per cent and 19 per cent, respectively.
Study leader Dr Peter Katzmarzyk, of Pennington Biomedical Research Center in Louisiana, said: “The results of this study indicate extended sitting time and TV viewing may have the potential to reduce life expectancy.
“Adults spend an average of 55 per cent of their day engaged in sedentary pursuits. A significant shift in behaviour is required to make demonstrable improvements in life expectancy.”
The results indicated that cutting the amount of time spent sitting down every day to under three hours would add an extra two years to life expectancy.
Restricting TV time to under two hours daily would extend life expectancy by 1.38 years.
Dr Katzmarzyk said: “Further research will be required before recommendations on safe levels of sedentary behaviour can be made.”
People in the UK watch an average four hours and 18 minutes of TV a day, according to TV marketing body Thinkbox.
It found that the growing popularity of digital TV channels had led to an increase in television viewing.
And a report by the Institute of Biology highlighted how the average child in the UK will have spent a total of one year watching television by the age of six.
It outlined 15 negative effects of watching TV from a young age, including increased risk of short-sightedness, sleep disorders and heart disease.