Physical activity, falls, and dementia risk in adults aged ≥ 60: evidence from three cohorts

Background Falls and physical inactivity are both linked to increased dementia risk, but their joint impact has not been well studied. It remains unclear whether physical activity can mitigate the elevated dementia risk after a fall and whether it also lowers the likelihood of future falls. Methods We used data from 44,488 adults aged ≥ 60 years in three cohorts. Falls and physical activity were self-reported. Incident dementia was tracked during follow-up. Cox proportional hazards models estimated the associations of falls with dementia and physical activity with dementia and falls, stratified by fall history. Results Over a median follow-up of 5.9–7.9 years, 3,492 dementia cases were identified. Falls were associated with a 70% higher risk of dementia (pooled HR = 1.70, 95% CI: 1.57–1.84). In the no-fall group, compared with inactivity, low, moderate, and high physical activity were progressively associated with lower risks of dementia (HRs = 0.63, 0.53, 0.43) and falls (HRs = 0.77, 0.68, 0.58). These protective effects were consistent among fallers, with similar dose–response gradients. Conclusions Falls substantially increased dementia risk. Higher levels of physical activity were linked to lower risks of both dementia and falls, regardless of fall history.