It has long been known that watching a lot of TV can have negative health effects. However, a new study reveals that TV watching is even worse than previously thought. Prolonged viewing has been linked with eight of the leading causes of death in the United States.

92 percent of all American homes have a TV set. 80 percent of adult Americans watch 3.5 hours of television a day. It is easily the most popular way to spend leisure time. But the more time spent in front of the tube, the higher the risk of death from such causes as cancer or heart disease.

The study was conducted by the National Cancer Institute (NCI) and published in the American Journal of Preventative Medicine. Researchers tracked the viewing habits of over 221,000 participants, all healthy and between the ages of 50 and 71.

“Older adults watch the most TV of any demographic group in the U.S.,” said Sarah K. Keadle, Ph.D., MPH, Cancer Prevention Fellow at National Cancer Institute. “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 results showed that those who watched the American average of three to four hours a day were 15 percent more likely to die from one of the leading causes of death. People who watched seven or more hours of TV a day were 47 percent more likely to be at risk compared with people who watched less than one hour a day.

“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,” said Dr. Keadle. “In this context, our results fit within a growing body of research indicating that too much sitting can have many different adverse health effects.”

Worryingly, daily exercise was not enough to mitigate the risks associated with excessive TV watching- active and inactive people both saw increased risk.

“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.

More research needs to be done in order to determine just how exactly TV viewing is linked with death. According to the CDC, the leading causes of death in America are 1) Heart disease: 611,105, 2) Cancer: 584,881, 3) Chronic lower respiratory diseases: 149,205, 4) Accidents (unintentional injuries): 130,557, 5) Stroke (cerebrovascular diseases): 128,978, 6) Alzheimer’s disease: 84,767, 7) Diabetes: 75,578, 8) Influenza and Pneumonia: 56,979, 9) Nephritis, nephrotic syndrome, and nephrosis (kidney diseases): 47,112, and 10) Intentional self-harm (suicide): 41,149.