Those who reported watching more than three hours of TV on a daily basis and exercised very little were twice as likely to score below average on two thinking tests.
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Tina Hoang, a researcher at the Veterans Affairs Medical Center in San Francisco said if the study were to happen today, it would include all the time young adults spend with screens other than TVs.
Watching a lot of TV and having a low physical activity level as a young adult were associated with worse cognitive function 25 years later in midlife, according to an article published online by JAMA Psychiatry. As such, 10.9 percent of the participants who had high TV watching levels consistently over the 25-year-span also had poor cognitive performance. Now evidence is building that being a couch potato earlier in your life may impair your brain, too.
Researchers in the U.S. say few studies have looked at how rates of physical activity in early adulthood can impact on cognitive function in later years.
After the 25 years, the researchers also examined the people’s cognitive function using three tests that assessed the speed at which they processed information, their verbal memory and executive function – a number of mental skills that help people plan, organize and pay attention.
More precisely, it may be that individuals with lower mental sharpness to begin with were the ones who had a stronger predilection for TV and for other more sedentary activities, shunning physical exercise.
As he explains, prior studies had also suggested that favoring a sedentary lifestyle might lead to cognitive impairment, whereas regular exercise can result in greater neuroplasticity, and neural rejuvenation.
When they looked at activity levels, they placed 528 people, or 16.3%, in this category and found that they tended to perform poorly in one of the tests. In return they associated with low results in cognitive performance tests, as well as in processing speed tests.
The researchers acknowledge some limitations to their study, mainly because TV watching and physical activity, was self-reported through questionnaires. That meant the amount of time they spent jogging, biking, swimming, hiking, playing tennis, doing yard work or getting other types of exercise was usually so low that it would have ranked in the bottom 25 per cent at the start of the study. The process that didn’t appear to be affected by watching TV was verbal memory.
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“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”, said the study. The findings are worth keeping in mind the next time you’re tempted to ditch boot camp and grab the remote instead.
