The number of hours spent watching TV is associated with an elevated risk of death, according to a recent study.

Researchers at the National Cancer Institute found that many hours of TV viewing was associated with eight of the leading causes of death in the United States, such as, diabetes, influenza/pneumonia, Parkinson's disease, and liver disease, the Milwaukee Journal Sentinel reported. About 92 percent of Americans have a television at home and watching TV consumes more than half of their available leisure time, potentially displacing more physical activities.

"We know that television viewing is the most prevalent leisure-time sedentary behavior and our working hypothesis is that it is an indicator of overall physical inactivity. In this context, our results fit within a growing body of research indicating that too much sitting can have many different adverse health effects," Sarah K. Keadle, lead investigator of the study, said in a statement.

For the study, researchers collected and analyzed data from more than 221,000 individuals aged 50-71 years old who were free of chronic disease at the start of the experiment, The Business Standard reported.

Researchers found that compared to those who watched less than one hour per day, individuals who reported watching three to four hours of television watching 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 to 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.

 "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," Keadle said.

Investigators caution that more research is needed to explore connection between TV viewing and mortality and whether these same associations are found when we consider sitting in other contexts, such as driving, working, or doing other sedentary leisure-time activities.

"Older adults watch the most TV of any demographic group in the U.S.," concluded Keadle. "Given the increasing age of the population, the high prevalence of TV viewing in leisure time, and the broad range of mortality outcomes for which risk appears to be increased, prolonged TV viewing may be a more important target for public health intervention than previously recognized."

The findings are detailed in the American Journal of Preventive Medicine.