Too Much TV, Too Little Exercise May Affect Cognitive Function Later On


A new study published in JAMA Psychiatry has found that young adults who spent hours in front of the television and who are not getting enough physical activity time had a tendency to have lower cognitive function as measured by standardized tests when they became middle aged.

According to Ariana Eunjung Cha of The Washington Post, the study took place over 25 years and followed 3,247 people starting at age 18 to 30 who were asked to answer questions about their TV viewing and exercise levels. The researchers required the participants to check-in at years, five, 10, 15, 20, and 25.

The subjects were chosen from Birmingham, Chicago, Minneapolis and Oakland, and they had a median age of 25.1-years-old when the study began. The split between men and women was approximately equal, and more than half of the volunteers were white and most of the rest were black. 93% of the participants had at least finished high school.

Three hundred and fifty-three of the volunteers said they watched more than three hours of TV a day for over two-thirds of the check-in procedures. This group was designated as having “high” viewing patterns. The rest of the subjects had moderate or low patterns of viewing.

Many studies have shown that those who are living sedentary lives can be hurting their bodies. Now, the increasing evidence from this research, partially funded by the National Heart, Lung, and Blood Institute, shows that being a TV watcher for many hours a day earlier in your life may result in brain impairment as well.

When the 25-year study ended, each person was given three cognitive tests. The first, the Digit Symbol Substitution Test, measured the rapidity at which a person could make sense of and carry out cognitive tasks. In IQ tests for children, the tasks consist of something like finding the bugs in a row of bugs that have the same characteristics.

This test is also concerned with an individual’s executive function and that is the measure of a person’s ability to manage resources and time to reach a goal. If a person is always losing his keys or has trouble being on time to work, that person probably has poor executive function.

The second test, the Stroop test, also touched on executive function. And the third, the Rey Auditory Verbal Learning Test, measured the recall of words or other language abstractions. The test is ordinarily assessed by having an individual recount a short story or a list of words.

The researchers adjusted for such things as smoking, alcohol use, BMI, age, sex, race and other factors.

The study’s author, Tina D. Hoang of the Northern California Institute for Research and Education at the Veterans Affairs Medical Center in San Francisco, said:

“Being physically active at any time in your life is good for your brain.”

Those in the study, writes Agata Blaszczak-Boxe of LivingScience, who watched more than three hours of TV daily, on average, were more likely to perform worse on some of the tests than those who watched a small amount of TV.

The participants who exercised least performed more poorly on one of the tests than those who were more physically active.

The group of individuals who watched more than three hours of TV daily and exercised the least were two times as likely to perform at a lower level on cognitive tests compared to those who exercised more and spent a smaller amount of time watching television.

The reason spending more time watching television is linked to poor cognitive performance in later life might be because watching TV is not a cognitively engaging activity, said Hoang. She also said it might be because people who watch higher amounts of television and do not exercise may have other unhealthy habits like a poor diet, which could also be linked to lesser cognitive function.

Andrew Przybylski, an experimental psychologist at the University of Oxford, who was not involved in the study, said that the data rely on a self-reported measure of television watching time, reported AFP. Also, the research team did not study subjects’ cognitive functioning at the beginning of the study. He added that almost one in three volunteers left the study before it was completed.

ScienceDaily reports that the authors acknowledged a few limitations of the study, one of which is possible selection bias and the fact that physical activity levels and TV viewing times were self-reported.