A major new analysis suggests that, when it comes to dementia risk, how people are physically active may matter as much as how much they move. Researchers from the University of Southern California (USC) found that leisure-time exercise, including activities such as walking, running, swimming and cycling, was associated with a significantly lower risk of dementia. In contrast, physical activity performed as part of a person's job was linked to a higher risk of the condition.
The findings come from a meta-analysis published in The Lancet Public Health that examined data from 74 cohort and case-control studies involving more than 4.2 million people across 30 countries. For years, studies have pointed to regular physical activity as a potential way to help reduce dementia risk. However, the new research suggests that lumping all forms of movement together may overlook important differences between recreational exercise and workplace physical activity.
The researchers investigated whether a phenomenon known as the "physical activity paradox" might also apply to dementia. The paradox, already documented in cardiovascular research, refers to the observation that physically demanding occupations do not appear to provide the same health benefits as voluntary exercise and may even be associated with worse outcomes. Participants were between 45 and 93 years old and were followed for a median of 10 years.
During that period, researchers tracked diagnoses of all-cause dementia, Alzheimer's disease and vascular dementia. The analysis found that people who engaged in higher levels of leisure-time physical activity had a 24 percent lower risk of dementia compared with those who were the least active. Meanwhile, occupational physical activity was associated with a 20 percent higher dementia risk.
The study also found signs that household physical activity could be beneficial, although the evidence came from only one study. Active commuting, such as walking or cycling for transportation, was associated with a modest increase in risk, but those findings were based on just two studies. "The findings challenge the long-held assumption that 'every move counts' for brain health," said Natan Feter, the study's first author and a postdoctoral fellow in USC's Evolutionary Biology of Physical Activity Lab.
Feter told Newsweek that strenuous physical activity at work affects dementia risk differently than leisure exercise because it often involves repetitive, low-complexity tasks that may limit the accumulation of cognitive reserve. In contrast, leisure-time activity is more likely to be self-selected, varied, and socially engaging,” he said. The authors argue that movement itself is unlikely to explain the higher dementia risk associated with occupational physical activity.
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