This Is Your Brain on Too Much TV

Cognitive function in midlife linked to television, exercise patterns in young adulthood


Mom was right. It turns out watching too much TV really might hurt your brain.

A new study, which followed a large group of participants for 25 years, found that watching a lot of TV and getting little exercise in young adulthood may lead to poor cognitive function in midlife.

"In this biracial [group] followed for 25 years, we found that low levels of physical activity and high levels of television viewing during young to mid-adulthood were associated with worse cognitive performance in midlife," wrote lead study author Tina D. Hoang, MSPH, of the Northern California Institute for Research and Education, and colleagues. "Participants with the least active patterns of behavior (i.e., both low physical activity and high television viewing time) were the most likely to have poor cognitive function."

For this study, Hoang and team used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study to look at the TV and physical activity habits of 3,247 young adults from 1985 to 2011. Surveys were used to assess these patterns.

A pattern of high TV viewing was defined as watching TV for more than three hours per day more than two-thirds of the time. A pattern of low physical activity was defined as falling below the average activity levels for age and gender more than two-thirds of the time.

At the study's end, cognitive function was evaluated using three tests that assessed processing speed, executive function and verbal memory.

These researchers found that high TV viewing in young adulthood was tied to a 10.9 percent increased chance of poor cognitive function in midlife. Low physical activity was tied to a 16.3 percent increased chance.

The odds of poor cognitive performance in midlife were also almost two times higher for young adults with both high TV viewing and low physical activity patterns than for those with low TV viewing and high physical activity patterns.

In light of the increasing prevalence of sedentary, screen-based activities, Hoang and colleagues said this finding may be especially relevant for upcoming generations of young people.

This study was published Dec. 2 in the journal JAMA Psychiatry.

The National Heart, Lung, and Blood Institute, the University of Alabama at Birmingham, Northwestern University and the University of Minnesota and others funded this research.

Study author Dr. Yaffe served on boards for Takeda, Inc. and was a member of the Alzheimer’s Association Medical and Scientific Advisory Council.