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Watching three or more hours of television per day might put you at risk for an early death, according to a new study in the Journal of the American Heart Association.

The study, conducted by researchers at the University of Navarra, in Pamplona, Spain, sought to examine whether spending excess time watching television, being on the computer or driving was linked to an increased risk for early death.

The researchers gathered data on 13,284 healthy university graduates in Spain, with an average age of 37. They followed up with participants every two years, over the span of eight years, and surveyed them on topics including the number of hours they spent driving, watching television and on the computer.

At the end of the study period, 97 participants had died, and the researchers came to some surprising conclusions about the link between these activities and risk for early death.

“We observed that those in the lowest category of television viewing, those who watched television less than one hour a day, they have a very low risk for mortality,” study author Dr. Miguel Martinez-Gonzalez, professor and chair of the department of public health at the University of Navarra, told FoxNews.com.

However, those who watched more than three hours of television per day fared much worse – and had more than twice the risk of premature death compared to participants who watched less than one hour.

Notably, the researchers found no link between spending time on the computer, or driving, and the risk of premature death.

“We expected to find some association of higher mortality related to higher time driving or computer use, but found nothing…” Martinez-Gonzalez said. “Only for television watching, and it was stronger than we expected.”

The researchers suspect that watching large quantities of television is associated with a higher death risk because it is such a sedentary activity.

“We think that computer use or driving are not so sedentary because, in fact, you are using your muscles to move your hands, you have muscle tension and stress,” Martinez-Gonzalez said. “[Also], if you are working with the computer or driving, you feel responsible for what you are doing, whereas if you are watching television you have no responsibility for what’s going on whatsoever.”

Furthermore, watching television is an activity that is easily done in isolation – and previous research has shown that social isolation can be a contributor to premature death.

“The other reason we think television watching may be associated with higher mortality rate is a lot of time watching television every day could be a marker of isolation, being a lonely person with very little social support,” Martinez-Gonzalez said. “This is a proxy for isolation. So if you have low social support, your mortality risk is higher many times.”

The researchers plan to continue their study, hoping to discover whether watching television is a risk factor for particular causes of death – such as cardiac death, or cancer.

However, they noted that people shouldn’t be worried about sitting in front of the television to enjoy a favorite show– as long as they keep their viewing time in moderation.

“There is nothing bad in watching television, nothing wrong, unless you spend four or five hours a day,” Martinez-Gonzalez said. “In so far as you you watch television for a while, two to two-and-a-half hours a day, this is perfect, no association, no significant [increase in] risk for those categories. Only when there are three or more hours a day.”