Physical Activity and Dementia: A Work-Leisure Divide

Physical activity (PA) at work may not offer the same protection against dementia when performed as being physically active during leisure time, new research suggested.Results from a large meta-analysis showed that, over a median follow-up of 10 years, high levels of PA were associated with reduced risks for all-cause dementia, vascular dementia, and Alzheimer’s disease (AD) overall. However, leisure-time PA was associated with a 24% lower risk for dementia, whereas work-related PA was linked to a 20% higher risk.The findings challenge the notion that “every move counts” when it comes to dementia prevention, said lead author Natan Feter, PhD, a postdoctoral fellow at the University of Southern California (USC) in Los Angeles.“With an observational study, we cannot confirm that occupational activity will increase your risk for dementia; but we had a dose-response showing that the links we found were very consistent across cohorts. We were also surprised by the magnitude of the associations we found,” Feter told Medscape Medical News.The findings were published online on August 18 in The Lancet Public Health.The PA ‘Paradox’Feter noted that a PA “paradox,” where physically demanding jobs are not as beneficial as voluntary exercise, has been shown in previous cardiovascular research. His team wanted to see whether this paradox also applies to the risk for dementia.Although a previously published systematic review and meta-analysis showed a link between PA and reduced risk for dementia, many of the included studies only assessed leisure PA.For the current research, the investigators examined PA performed in other domains, including occupational, household, and commuting. They included 17 new studies plus the 57 studies from the previous review, all of which were published between 2021 and 2026, and included more than 4.2 million total participants aged 20 years or older (mean age, 67.3 years; 52.8% women) from 30 countries.Over a mean follow-up of 10 years, results showed a reduced risk for all-cause dementia (relative risk [RR], 0.80), vascular dementia (RR, 0.71), and AD (RR, 0.79) for high levels of PA compared with the lowest level of PA.There was also a reduction in all-cause risk for dementia for leisure-time and household PA (RRs, 0.76 and 0.85, respectively), but evidence for the latter came from a single study. The risk for dementia was increased for occupational and commuting PA (RRs, 1.20 and 1.10, respectively).“Our findings show that the association between [PA] and dementia risk is not uniform across activity contexts,” the investigators wrote. The results underscore the importance of considering how and where activity is accumulated rather than focusing solely on total levels, they added.The physical demands of work-related PA, along with job stress and hazardous environmental exposures, may help explain its association with an increased risk for dementia, Feter noted.However, he said the findings do not advocate for the avoidance of physically active jobs. Instead, he said they highlight the importance of adding in leisure-time PA whenever possible.“Improving access to safe parks, walking trails, and recreational facilities…and reducing harmful workplace exposures may ultimately prove as important as promoting physical activity itself,” co-investigator David Raichlen, MD, of USC, added in a release.Largest Study To DateIn an accompanying editorial, Mika Kivimäki, PhD, and Mark Hamer, PhD, both from University College London in London, England, wrote that this was the largest meta-analysis to date of observational studies examining PA and dementia.The editorialists also echoed Feter in noting that the finding of a link between occupational PA and increased risk for dementia is plausible for several reasons.“Physical activity itself does not become harmful simply because it occurs at work,” they wrote.But high PA jobs “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 added.On the other hand, they pointed out that recreational PA often includes social interaction and tasks that are cognitively demanding.Although meta-analyses of observational studies of recreational PA “remain susceptible to reverse causation,” PA overall still offers well-established health benefits, Kivimäki and Hamer noted.“Even if its effect on dementia proves to be smaller than suggested by the current meta-analysis, it remains one of the most worthwhile public health interventions,” they concluded.The study was funded by several organizations, including the National Institutes of Health, the state of Arizona, the Arizona Department of Health Services, and the McKnight Brain Research Foundation. Additional funding information and disclosure information for the study investigators are available in the original study publication. The editorialists reported no relevant financial relationships.