Several studies have associated physical activity with the risk of dementia, but mostly did so during short follow-up. It remains unclear whether physical activity also affects dementia during longer follow-up. We examined the association between physical activity and risk of dementia during a follow-up period up to 14 years. From 1997 to 1999, physical activity was assessed using a validated questionnaire in 4,406 elderly persons (age range 61-97) from the prospective, population-based Rotterdam Study. Follow-up for dementia was complete until January 1, 2011. We used Cox proportional hazards models to assess the association between physical activity and incident dementia. Next, we stratified follow-up time using a cut-off of 4 years. We separately investigated dementia due to Alzheimer disease. During 38,631 person-years, 583 participants developed dementia. When adjusting for age and sex, we found a borderline significant association between higher physical activity and lower risk of dementia (HR 0.95; 95 % CI 0.87-1.04). This association was confined to follow-up up to 4 years (HR 0.82; 95 % CI 0.71-0.95), and not to follow-up of at least 4 years (HR 1.04; 95 % CI 0.93-1.16). Additional adjustments only slightly attenuated the associations. A similar pattern was present for Alzheimer disease. We found a higher level of physical activity to be associated with a lower risk of dementia. This association was confined to follow-up for up to 4 years and not to longer follow-up, suggesting either a role for reverse causality or only a short term effect of late-life physical activity in an elderly population.

Alzheimer disease, Dementia, Physical activity, Risk factors,
European Journal of Epidemiology
Department of Neurology

de Bruijn, R.F.A.G, Schrijvers, E.M.C, de Groot, K.A, Witteman, J.C.M, Hofman, A, Franco, O.H, … Ikram, M.K. (2013). The association between physical activity and dementia in an elderly population: The Rotterdam Study. European Journal of Epidemiology, 28(3), 277–283. doi:10.1007/s10654-013-9773-3