Physical activity as a protective factor for dementia and Alzheimer's disease: systematic review, meta-analysis and quality assessment of cohort and case-control studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational cohort and case-control studies.
PubMed 35301183 · doi:10.1136/bjsports-2021-104981
What was done
A systematic review and meta-analysis of cohort and case-control studies identified across six databases (CINAHL, PsycInfo, Scopus, PubMed, Web of Science, SPORTDiscus) through October 2021. Eligible studies enrolled adults with at least 1 year of prospective follow-up, baseline cognitive or mid-life cohort assessment, and an estimate linking baseline physical activity to incident all-cause dementia, Alzheimer's disease, or vascular dementia (n=58 studies). Analyses included pooled effect sizes, dose-response modeling, moderation analyses by follow-up length (including ≥20 years), age, and quality, and funnel plot assessments.
What was found
Physical activity was associated with a lower risk of all-cause dementia (pooled relative risk 0.80, 95% CI 0.77 to 0.84, n=257,983), Alzheimer's disease (pooled relative risk 0.86, 95% CI 0.80 to 0.93, n=128,261), and vascular dementia (pooled relative risk 0.79, 95% CI 0.66 to 0.95, n=33,870). The association persisted in studies with ≥20 years of follow-up for all-cause dementia and Alzheimer's disease. Neither baseline age, follow-up length, nor study quality significantly moderated the effects. Dose-response meta-analyses found significant linear, spline, and quadratic trends for all-cause dementia, but only a significant spline trend for Alzheimer's disease. Funnel plots indicated potential publication bias for all-cause dementia and Alzheimer's disease.
Why it matters
Demonstrating that the protective association between physical activity and dementia persists across follow-ups of 20 years or more provides strong evidence against reverse causation.
Limits
All included evidence is observational (cohort and case-control studies), which cannot establish causality and remains vulnerable to confounding. Funnel plot asymmetry suggested potential publication bias for all-cause dementia and Alzheimer's disease. Specific exercise types, intensities, or definitions of physical activity were not detailed in the abstract.
Cited by
- supports Epidemiological research shows that exercise and physical activity are protective against Alzheimer's disease risk.