The journal Alzheimer’s & Dementia has just published an analysis of the effects of physical activity on preclinical risk factors for Alzheimer’s disease (AD) among middle-aged adults at higher risk for its development. Three hundred thirty-seven adults were recruited from a subset of a larger longitudinal cohort, the Alzheimer's and Families (ALFA) study. Participants were between the ages of 45-65, without cognitive impairment, though at higher risk (86% of participants in ALFA have at least one parent with AD).
Their physical activity was assessed at the beginning of the study, and again at a follow-up assessment approximately 4 years later. They were then grouped into one of 5 categories, depending on whether they were sedentary (no activity), adherent or non-adherent to WHO activity guidelines (≥150 min/week moderate or ≥75 min/week vigorous intensity), and if they maintained or changed activity levels over time. PET and MRI scans were performed at the follow-up visit to determine brain Aβ burden and cortical thickness in AD-vulnerable structures, indicators of AD risk.
The principal finding was that maintaining sedentary behavior was related to lower cortical thickness (greater AD risk), while becoming adherent to WHO guidelines (i.e., increasing from baseline activity) was associated with a lower brain Aβ burden, in comparison to becoming non-adherent. There also appeared to be a dose-dependent relationship between physical activity and lower levels of brain Aβ burden, with the data largely suggesting that increased physical activity has a protective effect. While reverse causality cannot be ruled out, i.e., that brain atrophy leads to more sedentary behavior, a protective effect of exercise is consistent with previous studies.