Background: Dementia is the second leading cause of death in the United Kingdom, affecting 7.1% of older adults. One in five dementia cases in Europe can be attributable to physical inactivity. We examined the association between physical activity at age 50 or older and risk of dementia over 15 years.
Methods: The English Longitudinal Study of Ageing (ELSA) comprises a national population-based cohort that began in 2002–03 (baseline) with 9275 individuals aged ≥50 years. Dementia diagnosis was followed over 15 years. Physical activity in daily life and at work was measured at baseline and at two yearly intervals and participants were categorized as inactive, low, or moderate-to-high active. Cumulative incidence of dementia during follow-up was calculated; hazard ratios and 95% confidence intervals (CI) were estimated using survival analysis.
Results: At baseline, 69% of the sample were categorized as moderate-to-high active. The inactive, low, and moderate-to-high active groups had a cumulative incidence of dementia of 4.8% (95%CI: 4.4 to 5.4), 0.9% (95%CI:0.8 to 1.1), and 0.2% (95%CI: 0.1 to 0.5), respectively. In adjusted analyses, participants in the low and moderate-to-high active groups had, respectively, 60% and 78% lower risk of developing dementia than the inactive group. Survival analyses showed large between-group differences in the cumulative incidence of dementia over 15 years based on the physical activity categories. Conclusion: In people aged 50 or more, there is an inverse dose-response association between physical activity and incidence of dementia over 15 years. Even low levels of physical activity have beneficial effects.