Spending long hours watching television during middle age may be linked to changes in brain structure later in life, according to a new long-term study that followed more than 1,700 adults for over two decades.
Researchers found that people who reported watching television "very often" during their leisure time between their 40s and 60s, the boomers, had smaller volumes in several brain regions when they underwent MRI brain scans in their mid-70s.
The findings remained significant even after accounting for factors such as age, sex, race, education, physical activity, smoking, body weight, diabetes and high blood pressure.
The study was conducted as part of the Atherosclerosis Risk in Communities (ARIC) Study, one of the longest-running health studies in the United States, involving 1,712 participants whose average age was 53 at the beginning of the study and 76 by the final brain assessment.
It's not just sitting - it's what you're doing while sitting
One of the study's key findings is that not all sitting appears to affect the brain in the same way.
Researchers found that frequent television watching, a largely passive activity, was associated with lower brain volume across several parts of the cerebral cortex.
In contrast, people who reported always sitting while working showed a slightly higher volume in a small area of the frontal cortex known as the frontal pole.
Scientists say this difference may be because office work often involves mentally demanding activities such as reading, writing, planning, solving problems and making decisions, whereas watching television generally requires much less mental effort.
The researchers cautioned, however, that this does not mean prolonged sitting at work is healthy.
Rather, the findings suggest that mentally passive sedentary behaviour may affect the brain differently from mentally active sedentary behaviour.
Which parts of the brain were affected?
The MRI scans showed lower volume in several regions of the brain involved in:
Memory and learning
Attention and concentration
Planning and decision-making
Language processing
Visual processing
Executive function
These areas help people remember information, solve problems, make decisions and perform everyday tasks.
Researchers said lower brain volume in these regions has previously been linked to cognitive decline and dementia risk, although the current study did not conclude that television watching directly causes dementia or brain shrinkage. It found only an association between heavy TV viewing and brain structure.
Men and Women
The study included 981 women (57.3 per cent) and 731 men (42.7 per cent).
Researchers adjusted their analysis to account for sex, meaning the association between frequent television viewing and lower brain volume remained regardless of whether participants were male or female.
The study did not report that men were more affected than women, or vice versa. Researchers also accounted for several lifestyle and health factors that could affect brain health.
Among participants:
About one in four had high blood pressure, nearly six per cent had diabetes, around 41 per cent were overweight, about one-quarter were obese, and nearly half had never smoked.
Even after adjusting for these factors, the association between heavy television viewing and lower brain volume remained.
While the findings do not prove that watching television causes brain changes, health experts say there are simple habits that may help protect brain health:
Avoid sitting for several hours without taking a break.
Stand up and walk around every 30 to 60 minutes.
Replace some television time with activities that challenge the brain, such as reading, learning a new skill or solving puzzles.
Aim for at least 150 minutes of moderate physical activity each week.
Control blood pressure, diabetes and cholesterol.
Get enough sleep and maintain a healthy diet.
Previous research has also shown that mentally engaging activities, even while sitting, may be better for long-term brain health than passive screen time.
Activities such as crocheting, knitting, tailoring, reading the newspaper or a book, studying, playing chess, solving puzzles, learning a new skill online, writing, or even managing business records and accounts stimulate the brain more than passively watching television.
For many people, especially our parents or people in the older generation, relaxing in front of the television after work is part of daily life. However, this long-term study suggests that how you spend your sitting time may matter as much as how long you spend sitting.
Researchers say replacing some passive television viewing with mentally stimulating activities and regular movement could help support brain health as people grow older, though further studies are needed to determine whether changing these habits can prevent cognitive decline.
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