Watching television for more than three to four hours a day is linked to eight leading causes of death in US, including cancer, heart disease and diabetes, researchers have claimed.
Previous studies had reported a relationship between TV viewing and elevated risk of death from cancer and cardiovascular disease.
In this study, researchers at the National Cancer Institute in US looked at more than 221,000 individuals aged 50-71 years old who were free of chronic disease at study entry.
They confirmed the association for higher mortality risk from cancer and heart disease.
In addition, they identified new associations with higher risk of death from most of the leading causes of death in the US, such as, diabetes, influenza/pneumonia, Parkinson's disease, and liver disease.
"We know that television viewing is the most prevalent leisure-time sedentary behaviour and our working hypothesis is that it is an indicator of overall physical inactivity," said lead investigator Sarah K Keadle, from the US National Cancer Institute.
"In this context, our results fit within a growing body of research indicating that too much sitting can have many different adverse health effects," said Keadle.
The study found that compared to those who watched less than one hour per day, individuals who reported watching 3-4 hours of television watching per day were 15 per cent more likely to die from any cause.
Those who watched 7 or more hours were 47 per cent more likely to die over the study period. Risk began to increase at 3-4 hours per day for most causes they examined.
The researchers took a number of other factors into consideration that might explain the associations observed, such as caloric and alcohol intake, smoking, and the health status of the population, but when they controlled for these factors in statistical models, the associations remained.
The detrimental effects of TV viewing extended to both active and inactive individuals.
"Although we found that exercise did not fully eliminate risks associated with prolonged television viewing, certainly for those who want to reduce their sedentary television viewing, exercise should be the first choice to replace that previously inactive time," said Keadle.
The study was published in the American Journal of Preventive Medicine.
