There seems to be an infinite fund of resources for any epidemiological research that involves television. Here researchers are trying to get a handle on the degree to which sedentary behavior negatively influences health, but their data strongly suggests that the correlation between increased mortality rates and more time spent watching television is only a correlation, as other similar forms of sedentary behavior do not show the same relationship, or at least not in this group of younger study participants.
Thus we are left reaching for the web of other factors that correlate with fewer hours spent watching television, such as wealth, education, intelligence, and so on - all of which themselves correlate with greater life expectancy. This is the challenge inherent in this sort of study, where obtaining even simple answers to simple questions from the data can be a struggle. There is plenty of evidence from other studies to suggest that less exercise and more time spent sitting both increase mortality rates, but when different - but really very similar - sitting activities have widely divergent statistical relationships with health it seems necessary to ask harder questions about the underlying mechanisms.
Adults who watch TV for three hours or more each day may double their risk of premature death compared to those who watch less. "Television viewing is a major sedentary behavior and there is an increasing trend toward all types of sedentary behaviors. Our findings are consistent with a range of previous studies where time spent watching television was linked to mortality."
Researchers assessed 13,284 young and healthy Spanish university graduates (average age 37, 60 percent women) 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 were followed for a median 8.2 years. Researchers reported 97 deaths, with 19 deaths from cardiovascular causes, 46 from cancer and 32 from other causes.
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.
Researchers found no significant association between the time spent using a computer or driving and higher risk of premature death from all causes. Researchers 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.