Too much TV and sitting lower brain power with time

Participants with the least active patterns of behaviour (i.e., both low physical activity and high television viewing time) were the most likely to have poor cognitive function.

And the 528 people in the study who exercised the least performed worse on one of the tests than the people who were more physically active, the researchers found. The median age of the participants, who were recruited from Birmingham, Ala., Chicago, Minneapolis and Oakland, Calif., was 25.1 years at start, with about an even split between men and women.

A study by Public Health England suggested that children who watched a lot of TV and took little exercise were more likely to be anxious. “Their verbal memory, however, seemed to be unaffected”.

Nearly 11 per cent of those who took part watched more than three hours TV a day and were more likely to have poor cognitive performance.

In the 25-year study, researchers followed 3,247 people starting at age 18 to age 30 and had them fill out questionnaires about their television viewing and physical activity during repeated check-ins at years five, 10, 15, 20 and 25 of the study.

In addition, 16 per cent of the participants qualified as having “a long-term pattern of low physical activity”.

High television viewing was defined as watching TV for more than three hours per day for more than two-thirds of the visits and exercise was measured as units based on time and intensity.

Researchers believe that it may be the fact that television is not cognitively engaging or that watching TV is typically done while sitting and can promote an unhealthy lifestyle if done too much, when exercise early in life and on can help preserve cognitive function.

The study has been published online by JAMA Psychiatry.

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.

“Some TV shows can be cognitively stimulating, and there’s some evidence that cognitively stimulating activities can be protective and beneficial”, says Margie Lachman, a psychologist at Brandeis University who was not involved in the study.

“In particular, these behaviours were associated with slower processing speed and worse executive function but not with verbal memory”, the researchers wrote.

The study findings focus mainly on young adults, stressing that those who watch a lot of television and engage in very little physical activity in their 20s tend to have worse cognitive function when they hit middle age. There were 107 participants, or 3.3% of the total, in this category.