People who watch television more than two hours a day could double their risk of early death.

Past research has indicated a link between the two, but a new study has provided evidence that strengthens that link. Published in the Journal of the American Heart Association on June 25, the study examined viewing habits of 13,000 Spanish adults to attempt to determine the relationship between watching television and premature death.

After ensuring that no one had health concerns such as heart disease, diabetes or cancer that could skew the results, scientists followed the participants for eight years, comparing the rate of early death with various sedentary activities. No link between premature death and activities such as driving or computer usage were found. The same was most certainly not true of TV viewing habits.

Every two hours of additional viewing time added significantly to the risk of various life-threatening diseases. When compared to people who claimed to watch less than an hour of television a day, the risk of death from cancer went up 21 percent, for heart disease it increased 44 percent and for other diseases, the risk went up a combined 55 percent.

The results were pronounced enough that even the scientists involved in the study were hesitant to trust the data. After all, finding a link, even a strong one, does not ensure that one causes the other, or vise versa.

The research team controlled for other factors that may have influenced the outcome. They eliminated 35 deaths that may have indicated that poor health lead to longer hours in front of the television set. They controlled for people’s tendency to eat more processed or sugar laden foods while watching TV. They controlled for age, weight, gender, histories of smoking and more. The effect of these controls on the results only served to strengthen the connection.

Experts are not ready to say for certain that television itself is responsible for the hike in risks involving death. Critics of the study point out that not every factor has been considered and suggest that early death is less directly related to television watching than current results suggest.

Time spent watching television is time not spent moving about. Even other sedentary activities, such as computer use or driving, still involve small movements and muscle tension. Watching TV does not even employ these small demands from muscles.

All research still indicates that limiting television and other sedentary activities in favor of healthy eating and exercise are the best ways to lower the risk of early death.