Exercise Lowers Dementia Risk—But There’s a Surprising Catch, Study Finds

For years, experts have emphasized the importance of exercise and physical activity in reducing dementia risk—and for good reason. Research shows that people who exercise regularly may be up to 20% less likely to develop dementia than those who don’t.

But is all physical activity created equal? According to a new study, the answer may depend on when, where, and why you’re moving.

Researchers from the University of Southern California (USC), Brown University, University of Arizona, University of Illinois, and several international institutions published their findings in The Lancet Public Health. They suggest exercising for fun and being active at work may have two different affects on risk.

What the study found about exercise and dementia risk

For their meta-analysis, researchers analyzed data from 74 studies involving more than 4.2 million participants across 30 countries. The studies followed participants for a median of 10 years and tracked diagnoses of all-cause dementia, Alzheimer’s disease, and vascular dementia.

Researchers conducting the meta-analysis looked at all of those studies to examine how the type of physical activity—whether for leisure or work—was associated with dementia risk. Leisure-time activities could include walking, cycling, running, swimming, and playing sports. Occupational physical activity may include heavy lifting, repetitive physical tasks, and prolonged standing.

Unsurprisingly, they found that the groups of more physically active people were at less risk for dementia. But how and when a person moved their body made a big difference.

Specifically, participants who engaged in higher levels of leisure-time physical activity had a 24% lower risk of dementia than those who were least active. While participants with higher levels of occupational physical activity had a 20% higher dementia risk.

The researchers also examined household activities and commuting to work. They found that household physical activity appeared beneficial—though evidence came from only a single study. And active commuting showed a modest increase in dementia risk, but the findings were based on just two studies.

Why researchers think it matters

The researchers suggest that leisure-time physical activity may offer different benefits partly because people can choose when and how they do it, rather than their jobs dictating their movement. It can also involve a more enjoyable pace, opportunities for social interaction, and stress reduction. On the other hand, physically demanding jobs may involve more psychosocial stress, less job control, hazardous working conditions, and greater exposure to air and noise pollution, all of which the researchers note have been linked to dementia risk.

Of course, this doesn’t mean you should quit or avoid physically demanding jobs. Because the analysis was observational, it showed an association—not that occupational physical activity causes dementia. Instead, the findings highlight the importance of considering context when it comes to being active.

What movement they recommend

Ultimately, the findings challenge the idea that all physical activity offers the same benefits—and suggest that instead of simply encouraging people to “move more,” we should recognize that the conditions surrounding physical activity may matter just as much as the movement itself.

“In other words, when it comes to protecting the brain, the context of physical activity may matter just as much as movement itself,” says senior researcher David Raichlen, PhD, USC professor of biological sciences and anthropology, in a press release. “Improving access to safe parks, walking trails and recreational facilities, ensuring people have adequate leisure time for exercise, and reducing harmful workplace exposures may ultimately prove as important as promoting physical activity itself.”

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