The Framingham Study Original cohort is a longitudinal community-based sample evaluated biennially since 1948 for cardiovascular risk factors. The physical activity index (PAI), a 24 hour, subject-specific measure of level of physical activity, based on estimating hours spent performing specific activities and weighting each activity by an assigned caloric equivalent, was measured during the 20th examination cycle (1986-87). Dementia- free participants who attended the 20th examination cycle and had available PAI were eligible for the present investigation (n=1,211; 742 F; age 76+5) PAI scores were divided into quintiles, from low (Q1) to highest (Q5), with Q1 referent. All participants were followed prospectively for the development of incident dementia and Alzheimer’s disease (AD) according to DSM-IV/NINCDS-ADRDA criteria.
Over two decades of follow-up (mean 9.9 +/-5 years), 242 participants developed dementia (193 AD). We observed that participants who reported moderate to heavy physical activity had a lower risk of all-cause dementia (HR=0.55, 95% C.I.0.37-0.81;p=0.003) after adjusting for age and sex. Further, participants in the lowest quintile of PAI (Q1) had an increased risk of incident dementia compared to those in higher quintiles (HR=1.45, 95% C.I. 1.06-1.98,p=0.021). Similar results were seen when analyses were limited to incident AD alone, and when excluding persons with mild cognitive impairment at baseline. Stratified analyses showed that the associations observed were largely evident in men.
Moderate to heavy physical activity is associated with a reduced risk for dementia, for up to two decades of follow-up. Our data emphasize that a reduced risk of dementia may be one additional health benefit to adults of maintaining at least moderate physical activity.