Watching television for three or more hours a day may double your risk of premature death, compared to those who watch less, says new research published in the Journal of the American Heart Association.

Researchers studied 13,284 young and healthy Spanish university graduates -- 60 percent of which were women, with an average age of 37 years -- to test the link between three specific types of sedentary behaviors and risk of death from any cause.

The activities under scrutiny were: watching television, sitting at a computer and riding in an automobile.

According to a heart association news release, the participants were followed for a median 8.2 years and in that time researchers reported 97 deaths, 46 from cancer, 19 from cardiovascular conditions and 32 from other causes.

The study found the risk of death for study subjects who reported watching three or more hours of television daily was twice as high as for those who watched one hour a day or less.

On the other hand, study scientists did not find any notable association between a higher risk of premature death and the time spent using a computer or driving.

"Television viewing is a major sedentary behavior and there is an increasing trend toward all types of sedentary behaviors," Miguel Martinez-Gonzalez, the study's lead author and professor and chair of the Department of Public Health at the University of Navarra in Pamplona, Spain, said in the news release. "Our findings are consistent with a range of previous studies where time spent watching television was linked to mortality."

The study cited previous research that suggests approximately half of all adults in the United States lead sedentary lives.

The American Heart Association recommends getting at least 150 minutes of moderate-intensity aerobic activity, or at least 75 minutes of vigorous aerobic activity, each week. Individuals should also do moderate- to high-intensity muscle strengthening at least two days a week.

"As the population ages, sedentary behaviors will become more prevalent, especially watching television, and this poses an additional burden on the increased health problems related to aging," Martinez-Gonzalez said. "Adults may consider increasing their physical activity, avoid long sedentary periods, and reduce television watching to no longer than one to two hours each day."

Researchers said added studies are will be necessary to confirm what effects, if any, computer usage and driving may have on death rates, as well as explain biological mechanisms behind such associations.