People who watch TV for three hours or more each day may be twice as likely to die prematurely than those who watch less, according to new research published Wednesday in the Journal of the American Heart Association.

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

The researchers assessed 13,284 young and healthy Spanish university graduates to determine the association between three types of sedentary behaviors and risk of death from all causes: television viewing time, computer time and driving time.

The participants, whose average age was 37 and 60 percent of whom were women, were tracked for a median of 8.2 years. In the end, 97 deaths were reported, including 19 deaths from cardiovascular causes, 46 from cancer and 32 from other causes.

The study showed that the risk of death was twofold higher for participants who reported watching three or more hours of TV a day compared to those watching one or less hours.

This twofold higher risk was also apparent after accounting for a wide array of other variables related to a higher risk of death.

The researchers found no significant association between the time spent using a computer or driving and higher risk of premature death from all causes.

They said further studies are needed to confirm what effects may exist between computer use and driving on death rates, and to determine the biological mechanisms explaining these associations.

"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. "Our findings suggest 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."