Men who engage in leisure-time moderate to vigorous physical activity (MPVA) may be at lower risk for disabling dementia, according to study findings published in JAMA Network Open.

Dementia is a leading cause of disability and dependency among older people. Some studies have shown that physical activity may reduce dementia incidence, while others suggest those results involve reverse causation bias. Few epidemiological studies have focused on the association between daily total physical activity and risk for dementia. In this study, researchers in Japan examined whether daily total MPVA in total time and leisure-time are linked with risk for dementia, with long-term follow-up and a large cohort.

Researchers analyzed data of 43,896 (aged mean 61.0±7.5 years; 53.9% women) of the 140,420 individuals who participated in the Japan Public Health Center-based Prospective Study (JPHC) based on availability of follow-up data on disabling dementia, whether they fulfilled JPHC criteria, and completion of a 10-year follow-up questionnaire. They identified disabling dementia cases based on certification records in the national LTCI system and assessed physical activity based on the 10-year follow-up survey.


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Participants reported the number of hours spent sitting, standing, walking, and completing strenuous work in nonleisure time on a typical day in the past year and the frequency and number of hours spent walking slowly, completing light to moderate exercise and strenuous exercise in leisure time.

During a dementia ascertainment period of 9.5±2.8 years, 5010 participants were diagnosed with dementia, 11,077 participants died, 2287 participants moved away, and 6 were lost to follow-up.

Participants with high daily physical activity tended to be younger, have lower body mass index (BMI), be never smokers, drink more, have less unemployment, and have less diabetes and hypertension.

Leisure-time MVPA was inversely associated with disabling dementia risk in men even after excluding individuals diagnosed within the first 9 years (Q4 vs Q1: aHR, 0.72 [95% CI, 0.56-0.92]; P for trend = .004) and after excluding participants diagnosed within 10 years. Inverse associations between daily total physical activity and risk for dementia, total MVPA and risk for dementia, and leisure-time MVPA and risk for dementia in women disappeared when participants diagnosed with dementia within 7 years of baseline were excluded in men and within 8 years were excluded in women.

The researchers said more leisure-time MVPA among men could protect from dementia because, as studies have previously reported, combined cognitive and exercise training and social activity may improve cognitive functions of community-dwelling older adults.

The association may have been attenuated in women because they already tend to engage in “many cognitive activities through daily housework activities, and are likely to have a larger social network than men,” the researchers noted.

Study limitations included the inability to assess the association between physical activity and specific types of dementia, eliminate misclassification in diagnosis of disabling dementia, or obtain information on education of all participants. Selection bias and misclassification of exposure due to changes in physical activity during the dementia ascertainment period may have also been present.

Reference

Ihira H, Sawada N, Inoue M, et al. Association between physical activity and risk of disabling dementia in Japan. JAMA Network Open. Published online March 29, 2022. doi: 10.1001/jamanetworkopen.2022.4590