The findings of the study are published in the December issue of the American Journal of Preventive Medicine.
Lead investigator Sarah K. Keadle, PhD, MPH, Cancer Prevention Fellow, Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute explained, "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."
An earlier study in 2014 reported that adults who watch TV for three hours or more each day may double their risk of premature death compared to those who watch less, according to new research published in the Journal of the American Heart Association.
Almost everyone in the U.S. has a TV at home or office and watching the idiot box eats up over 50% of their available leisure time, potentially displacing more physical activities. Earlier studies had reported a relationship between TV viewing and elevated risk of death from cancer and cardiovascular disease.
During the study, researchers at the National Cancer Institute studied over 221,000 individuals aged 50-71 years old who were free of chronic disease at study entry. They also found new links with higher risk of death from most of the leading causes of death in the U.S., such as, diabetes, influenza/pneumonia, Parkinson's disease, and liver diseas
Dr. Keadle warned that though each of the associations seen have plausible biological mechanisms, several associations are being reported for the first time and additional research is needed to replicate these findings and to understand the associations more completely. "Our study has generated new clues about the role of sedentary behavior and health and we hope that it will spur additional research."
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% more likely to die from any cause; those who watched 7 or more hours were 47% more likely to die over the study period.
Risk shot up at 3-4 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 significant result 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," said Dr. Keadle.
However, researchers said that there need to be further studies to explore the link between TV viewing and death rate and if these links 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 Dr. Keadle.
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