A study published in the journal Alzheimer's & Dementia, which followed more than 1,700 adults for nearly 24 years, found that men who frequently watched television in midlife showed reductions in brain volume.
Researchers said the shrinkage occurred in brain regions that are particularly vulnerable to Alzheimer's disease and was linked to increased damage associated with cognitive decline.
The same study found that people who spent much of the day sitting but used that time to solve puzzles, answer emails or engage in mentally demanding tasks maintained healthier brain structures.
The gender difference revealed by the research surprised scientists. The link between television viewing and changes in brain structure was much stronger in men than in women.
Experts said this may be related to women interrupting their sitting time more often or to biological differences between the sexes. They also noted that women may be more likely to watch television in shorter sessions, while men may spend longer, uninterrupted periods on the couch watching sports events and films.
Researchers from the University of Southern California emphasized that for years, studies focused only on how long people sit, but what they do while sitting is also a critical factor for brain health.
Watching television is considered a mentally passive activity, while desk work involves mental processes such as planning, reading, writing and problem-solving. Such stimulating activities help build "cognitive reserve," which increases the brain's resilience against aging.
The findings showed that even regular exercise does not fully offset the negative effects of prolonged television viewing. Experts recommend that people who spend long periods in front of screens take frequent breaks to help protect brain health.
