How much TV you watch as a young adult may affect midlife cognitive function

Participants with high television viewing (more than three hours per day for more than two-thirds of the visits) during 25 years were more likely to have poor cognitive performance on some of the tests. Low physical activity (measured as units based on time and intensity) during 25 years was associated with poor performance on one of the tests. The odds of poor cognitive performance were almost two times higher for adults with both high television viewing and low physical activity.

These behaviors were associated with slower processing speed and worse executive function but not with verbal memory. Participants with the least active patterns of behavior (both low physical activity and high television viewing time) were the most likely to have poor cognitive function. … Individuals with both low physical activity and high sedentary behavior may represent a critical target group, the study concludes.

The authors acknowledge a few limitations, including possible selection bias and that physical activity and TV viewing were self-reported. (Also, correlation does not imply causation.)

* Tina D. Hoang, M.S.P.H., of the Northern California Institute for Research and Education at the Veterans Affairs Medical Center, San Francisco, Kristine Yaffe, M.D., of the University of California, San Francisco, and coauthors.