The Relationships between physical activity, sedentary behaviour, sleep, and dementia: A systematic review and meta-analysis of cohort studies.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of prospective cohort studies
PubMed 41950182 · doi:10.1371/journal.pone.0343621
What was done
Authors conducted a systematic review and random-effects meta-analysis of prospective cohort studies (searches up to August 2025 across CINAHL, EMBASE, MEDLINE, PSYCINFO, and SPORTDISCUS). Eligible studies followed community-dwelling adults aged 35 years and older without baseline dementia for at least one year. Primary exposures were defined using national thresholds: regular physical activity, prolonged sedentary behaviour (8+ hours/day sitting), and sleep duration (<7 hours and >8 hours vs. 7–8 hours reference). The outcome was pooled risk ratios (RR) with 95% confidence intervals (CI) for incident dementia.
What was found
- Physical activity (49 studies, n = 2,855,529): Regular physical activity significantly reduced incident dementia risk (pooled RR = 0.75, 95% CI: 0.68 to 0.82; substantial heterogeneity). - Sedentary behaviour (3 studies, n = 295,809): Prolonged sitting (8+ hours/day) increased dementia risk (RR = 1.27, 95% CI: 1.17 to 1.39; low heterogeneity). - Sleep duration (17 studies, n = 1,344,170): Compared to 7–8 hours/night, higher dementia risk was observed for both short sleep (<7 hours; RR = 1.18, 95% CI: 1.09 to 1.28) and long sleep (>8 hours; RR = 1.28, 95% CI: 1.15 to 1.43; moderate to substantial heterogeneity).
Why it matters
This meta-analysis synthesizes large-scale prospective cohort data confirming that physical activity, avoiding excessive sedentary time, and maintaining 7–8 hours of sleep are modifiable behaviors associated with reduced dementia risk.
Limits
All included evidence is prospective observational, leaving potential for residual confounding and reverse causation from prodromal dementia. Sedentary behaviour analysis was limited to only three studies. Substantial statistical heterogeneity was present for physical activity and sleep outcomes. Changes in movement behaviours over time were not evaluated, and grey literature was excluded.
Cited by
- supports Physical activity and exercise significantly reduce the risk and assist in the prevention of dementia and Alzheimer's disease.