Regular physical activity has long been associated with a lower risk of dementia. New research led by the University of Southern California, however, suggests that the context of that activity — whether it occurs during leisure time or at work — may be as important as the amount of movement.

The meta-analysis, published in *The Lancet Public Health*, reviewed 74 cohort and case-control studies involving more than 4.2 million participants between the ages of 45 and 93 in 30 countries. Participants were followed for a median of 10 years while researchers tracked diagnoses of all-cause dementia, Alzheimer’s disease and vascular dementia.

People with higher levels of leisure-time physical activity had a 24% lower risk of dementia than those who were least active. Leisure activities included walking, cycling, running, swimming and playing sports.

In contrast, occupational physical activity was associated with a 20% higher risk of dementia. Active commuting was linked to a modest increase in risk, although that finding was based on only two studies. Household activity appeared beneficial, but evidence came from a single study and requires further investigation.

“The findings challenge the long-held assumption that ‘every move counts’ for brain health,” said first author Natan Feter, a postdoctoral researcher in USC’s Evolutionary Biology of Physical Activity Lab.

Researchers noted that exercise, manual labor, housework and commuting are often combined under the general term “physical activity,” even though they occur under very different conditions.

Leisure-time exercise is generally self-directed, can be performed at a comfortable intensity and may include social interaction or stress relief. Physically demanding jobs, by comparison, can involve repetitive tasks, prolonged standing, heavy lifting, insufficient recovery time and exposure to workplace hazards.

The researchers emphasized that movement itself may not explain the association between occupational activity and higher dementia risk. Workplace stress, socioeconomic conditions and environmental exposures may also contribute. Because the analysis was based on observational studies, it does not establish a direct cause-and-effect relationship.

“When it comes to protecting the brain, the context of physical activity may matter just as much as movement itself,” said USC Professor David Raichlen.

The findings suggest that dementia-prevention policies should extend beyond simply encouraging people to move more. Expanding access to safe parks, walking trails and recreational facilities, providing adequate leisure time for exercise, and reducing harmful workplace exposures may also support long-term brain health.