We already knew that sitting can be dangerous for your health. Studies show sitting for long periods can raise the risk of heart disease; and one study suggested that sitting for more than six hours a day can cut up to two years of your life expectancy.

Interestingly, the type of sitting that you do may matter more than originally thought. A new study released on June 26 in the Journal of the American Heart Association suggests that different levels of sedentary activity can be more harmful than others, and that TV is among the worst. The study found that watching TV for three or more hours a day doubled the risk of an early death among their sample group.

The study followed more than 13,000 Spanish university graduates for about eight years. The researchers asked them to keep a log of their sedentary time to see if there was an association between sedentary behavior and risk of death. Participants were asked to note time spent watching TV, using the computer, or driving.

In the study, 97 of the original 13,000 died. Miguel Martinez-Gonzalez, the study's lead author and professor at the University of Navarra in Pamplona, Spain, found that individuals who spent more than three hours a day watching TV were twice more likely to die at an early age those who didn't. There was no correlation found with computer use or driving. (The study did not take into account the difference between watching TV on the computer or watching it on a television set.)

One reason for this may be that TV watching is a completely sedentary activity which uses almost no muscles, whereas someone who is using a computer for work or driving has to be somewhat attentive and focused.

"Television viewing is a major sedentary behavior, and there is an increasing trend toward all types of sedentary behaviors," said Martinez-Gonzalez.

What does this mean? You might want to consider reducing the amount of TV you watch to one or two hours a day, suggests Martinez-Gonzalez. He also suggested engaging in mild exercise, and being more active.

Another risk factor is the type of person who watches an excessive amount of TV. Martinez-Gonzalez said people who frequently watch television for three or more hours a day tend to be more isolated and less likely to engage in physical activities outside of their home.

The results of this study are inconclusive, and more research needs to be done. However, in the meantime you may want to cut something off of your DVR list and hit the pavement instead.