A 24-year study of 1,712 adults found that frequent TV watching in midlife correlated with smaller brain volumes and increased white matter damage, particularly in men, according to research published in Alzheimer’s and Dementia: Journal of the Alzheimer’s Association.
The study, led by researchers at the University of Southern California (USC) and involving the Atherosclerosis Risk in Communities (ARIC) study, tracked participants who reported watching television “very often” and compared their brain scans decades later. Results showed reduced volumes in regions linked to Alzheimer’s disease, including the frontal and occipital lobes, alongside higher white matter hyperintensity (WMH) volumes—a marker of cerebrovascular disease associated with cognitive decline.
TV Watching Linked to Brain Shrinkage, Study Finds
Participants who frequently watched television in midlife exhibited widespread structural differences
in their brains compared to those who seldom or never watched TV, according to the study. These changes included smaller volumes in areas vulnerable to Alzheimer’s disease and increased WMH, which is associated with stroke risk and dementia. The research followed 1,712 adults, average age 53, who enrolled in the ARIC study between 1987 and 1989, with brain scans conducted 24 years later.
For years we've focused on how much people sit. Our findings suggest we should also pay attention to what they're doing while they're sitting,
said David Raichlen, professor of biological sciences and anthropology at the USC Dornsife College of Letters, Arts and Sciences and a senior author of the study, in a statement cited by ScienceAlert. The study found that other sedentary activities did not have the same associations, indicating that what one does while sitting may matter much more than previously thought.
Men showed more pronounced effects, with stronger links between TV watching and brain structure
compared to women. Researchers proposed that men may accumulate sedentary time differently or have biological differences in how their brains respond to prolonged inactivity. This could be because men and women accumulate sedentary time differently—for example, women may interrupt their sitting more often—or because of biological differences in how the brain responds to prolonged sedentary behavior,
said Natan Feter from the University of Southern California told ScienceAlert.
Sitting at Work Linked to Healthier Brains Than TV Watching
Interestingly, participants who spent long hours sitting at work had larger frontal and occipital lobe volumes and lower WMH compared to frequent TV viewers. The study suggests that mentally engaging sedentary tasks, such as office work, may protect brain health, while passive activities like TV watching do not. Even sedentary office work often involves planning, reading, writing, decision-making, and problem-solving,
the study noted. Previous research has suggested these kinds of mentally stimulating activities may help build 'cognitive reserve,' allowing the brain to better cope with age-related changes.
The findings remained significant even after controlling for factors like physical activity, diabetes, and BMI. However, the study relied on self-reported data, which is less reliable than direct tracking. It used self-reported data from participants who estimated how much TV they watched or how much time they spent sitting at a desk, which is less reliable than objectively measured data,
the study acknowledged.
Sex-Specific Brain Changes and Unanswered Questions
The study revealed stark sex differences. In men, frequent TV watching was linked to smaller volumes in the frontal, temporal, parietal, subcortical deep gray matter, and Alzheimer’s disease-signature regions. In women, no such associations were found. In women, very frequent television viewing was not associated with any brain region,
the study noted. However, always sitting during work was linked to lower volume in the left rostral anterior cingulate cortex, but no other associations were identified in women.
Researchers suggested hormonal differences, lifestyle factors, or variations in brain aging could explain the gender gap. Males may be more vulnerable to the adverse physiological effects of SB,
the study proposed. However, the mechanisms remain unclear, and the study’s reliance on self-reported data limits conclusions. The data for the study came from 1,712 participants in the long-running Atherosclerosis Risk in Communities (ARIC) study,
the study stated, adding that future research could begin with a baseline MRI to more concretely demonstrate changes over time.
Implications for Health Recommendations
The findings challenge conventional advice to simply reduce sitting time. Instead, the study suggests that the nature of sedentary activities matters. For years we've focused on how much people sit. Our findings suggest we should also pay attention to what they're doing while they're sitting,
says David Raichlen.
Health professionals might need to advise patients to limit TV time and opt for cognitively engaging activities when sitting. For years we've focused on how much people sit. Our findings suggest we should also pay attention to what they're doing while they're sitting,
says David Raichlen. However, the research also highlights the need for more targeted interventions, as not all sedentary behaviors carry the same risks.
While the study does not prove causation, it adds to growing evidence that prolonged TV watching may harm brain health. We found that the links between TV watching and brain structure were much stronger in men than in women,
Natan Feter said. The research underscores the complexity of sedentary behavior and the importance of context in assessing its impact on health.
