Effect of physical activity on risk of Alzheimer's disease: A systematic review and meta-analysis of twenty-nine prospective cohort studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of prospective cohort studies
PubMed 37979700 · doi:10.1016/j.arr.2023.102127
What was done
A systematic review and random-effects meta-analysis searched PubMed, Embase, Cochrane Library, and Web of Science from inception to June 2023 for prospective cohort studies evaluating physical activity and incident Alzheimer's disease (AD). Effect sizes were summarized as hazard ratios (HR) with 95% confidence intervals, alongside subgroup analyses by physical activity intensity and follow-up duration.
What was found
Twenty-nine prospective cohort studies covering 2,068,519 participants were included. Overall, physical activity was associated with a decreased risk of incident AD (HR 0.72, 95% CI 0.65–0.80; fully adjusted HR 0.85, 95% CI 0.79–0.91). An inverse dose-response relationship was observed across intensity levels: high activity (HR 0.56, 95% CI 0.45–0.68) and moderate activity (HR 0.85, 95% CI 0.80–0.93) showed statistically significant risk reductions, whereas low activity did not (HR 0.94, 95% CI 0.77–1.15). The protective association was significant only in cohorts with less than 15 years of follow-up and disappeared in cohorts followed for 15 years or longer.
Why it matters
This review synthesizes large-scale prospective cohort data indicating that moderate-to-vigorous physical activity is tied to lower Alzheimer's risk, but the lack of an association beyond 15 years suggests preclinical disease may cause early activity reduction (reverse causality).
Limits
All included studies were observational cohorts, precluding causal inference. The disappearance of protective effects at follow-ups of 15 years or longer suggests potential reverse causation due to the long prodromal phase of AD. Methods for measuring physical activity and diagnosing AD varied across studies.
Cited by
- supports Epidemiological research shows that exercise and physical activity are protective against Alzheimer's disease risk.