You'll want your competent? doctor to reconcile these two.
Most Physical Activity Is Tied to Lower Dementia Risk, but This Type May Raise It
Key Takeaways
- Leisure-time exercise was associated with lower dementia risk in a large systematic review and meta-analysis.
- In contrast, occupational physical activity was associated with a higher risk of dementia.
- Physically demanding jobs may be tied to broader social and brain health risks, researchers suggested.
The relationship between physical activity and dementia risk may depend on whether the activity is recreational exercise or job-related labor, a study of more than 4.2 million people suggested.
High physical activity levels were linked to a 20% lower risk of all-cause dementia (relative risk [RR] 0.80, 95% CI 0.75-0.86) over 10 years compared with the lowest level of physical activity, reported Natan Feter, PhD, of the University of Southern California in Los Angeles, and colleagues in a systematic review and meta-analysis.
Leisure-time activities like walking, running, swimming, cycling, or playing sports followed a similar pattern and were tied to lower dementia risk (RR 0.76, 95% CI 0.65-0.88), the researchers wrote in Lancet Public Health. Household physical activity also appeared beneficial, but evidence was from a single study.
In contrast, occupational activity was associated with an increased dementia risk (RR 1.20, 95% CI 1.01-1.42), Feter and co-authors found. In addition, active commuting was tied to higher dementia risk based on two studies.
"The findings challenge the long-held assumption that 'every move counts' for brain health," Feter said in a statement.
The study is the first to systematically examine whether the physical activity paradox -- the observation that physically demanding jobs may not provide the same health benefits as voluntary exercise -- extends to dementia, the researchers noted.
Leisure-time exercise is often self-directed and may be accompanied by stress reduction, they said. Physically demanding jobs may involve more stress and hazardous environmental exposures.
"Physical activity itself does not become harmful simply because it occurs at work. Instead, occupational physical activity is closely linked to other characteristics that influence dementia risk," observed Mika Kivimäki, PhD, and Mark Hamer, PhD, both of the University College London, in an accompanying editorial.
"Jobs requiring high physical activity are more often manual occupations, which are held by workers with lower educational attainment, fewer opportunities for cognitively stimulating work, greater exposure to neurotoxic agents, and a higher prevalence of smoking and other risk factors than employees in so-called white collar occupations," Kivimäki and Hamer wrote.
Recreational movement might support cognitive health through several pathways, the editorialists suggested. "Many leisure activities involve social interaction and cognitively demanding tasks, particularly team and partner sports, which combine physical activity with cognitive engagement. Such activities could also reduce social isolation in later life, itself a risk factor for cognitive decline," they noted.
"However, meta-analyses of observational studies of leisure-time physical activity remain susceptible to reverse causation," Kivimäki and Hamer pointed out. "Individuals classified as physically inactive, particularly in studies with relatively short follow-up, might already be in the preclinical phase of dementia. Emerging cognitive impairment, apathy, and circadian rhythm disturbances can reduce leisure-time physical activity long before clinical diagnosis."
These factors don't argue against beneficial effects of physical activity on brain health, they emphasized: "Rather, they suggest that reverse causation might have exaggerated the magnitude of the observed protective association between leisure-time physical activity and dementia," they wrote.
The systematic review and meta-analysis from Feter and colleagues spanned 74 cohort and case-control studies from January 2021 to May 2026 and included 4.23 million people. Participants had a median baseline age of 67.3, and about half (52.8%) were women. Most studies (93%) were conducted in high-income countries.
Eligible studies assessed all-cause dementia, Alzheimer's disease, or vascular dementia using validated cognitive assessments or registry data. They also evaluated physical activity using objective measures or self-reported questionnaires and included a reference group. Depending on age, a baseline cognitive assessment was required to reduce the chance of including people with prodromal dementia.
Over a median follow-up of 10 years, 64,009 all-cause dementia cases (median incidence 8.4%), 5,859 Alzheimer's cases (5.4%), and 1,607 vascular dementia cases (3.2%) were reported. Compared with the lowest level of physical activity, high physical activity levels were associated with reduced risks of both Alzheimer's disease (HR 0.79, 95% CI 0.70-0.90) and vascular dementia (HR 0.71, 95% CI 0.58-0.87).
Limitations included self-reported physical activity in most studies, the researchers acknowledged. Studies assessing household activity and workplace commuting were sparse, and the possibility of reverse causation cannot be excluded, they added.
This research was supported by grants from the NIH, the Arizona Department of Health Services, and the McKnight Brain Research Foundation. It was financed in part by the Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, the National Council for Scientific and Technological Development in Brazil, and the Department of Science and Technology of Secretariat of Science, Technology, Innovation, and Health Complex of Ministry of Health of Brazil.
Feter had no competing interests. One co-author reported relationships with the Orion Research Foundation and the Biomedicum Helsinki Foundation.
Kivimäki and Hamer had no competing interests.
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