Watching excess TV linked to poor brain function in later life: study

Los Angeles: Young adults who watch TV for more than three hours daily and have low level of physical activity may show poor cognitive function 25 years later in midlife, a new study has found.

Few studies have investigated the association between physical activity in early adulthood and cognitive function later in life.

Coupled with the increasing prevalence of sedentary or screen-based activities, such as watching television, these trends are of concern for upcoming generations of young people.

Tina D Hoang of the Northern California Institute for Research and Education at the Veterans Affairs Medical Centre, Kristine Yaffe of the University of California, San Francisco and coauthors examined associations between 25-year patterns of television viewing and physical activity and midlife cognition.

The study of 3,247 adults (ages 18 to 30) used a questionnaire to assess television viewing and physical activity during repeated visits over 25 years.

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.

Cognitive function was evaluated at year 25 using three tests that assessed processing speed, executive function and verbal memory.

Participants with high television viewing during 25 years (353 of 3,247 or 10.9 per cent) were more likely to have poor cognitive performance on some of the tests.

Low physical activity during 25 years in 528 of 3,247 participants (16.3 per cent) 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 in 107 of 3,247 (3.3 per cent) participants, according to the results.

"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," the researchers wrote in the study published in the journal JAMA Psychiatry.

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

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

"Individuals with both low physical activity and high sedentary behaviour may represent a critical target group," the study concluded.