Viewing television for over three-four hours daily is associated with increased risk of mortality from most of the major causes of death including cancer and heart diseases, warns a new study.
"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," explained lead investigator Sarah Keadle from the US National Cancer Institute, Bethesda, Maryland.
"In this context, our results fit within a growing body of research indicating that too much sitting can have many different adverse health effects," Keadle noted. In this study, the researchers 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 between excessive TV viewing and 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.
After an average follow-up of 14.1 years, the study found that compared to those who watched less than one hour per day, individuals who reported watching three-four hours of television per day were 15 percent more likely to die from any cause.
Those who watched seven or more hours were 47 percent more likely to die over the study period. Risk began to increase at three-four hours per day for most causes they examined.
The investigators 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.
Another important finding of the study is that the detrimental effects of TV viewing extended to both active and inactive individuals. The study was published in the American Journal of Preventive Medicine.