Exercise and Alzheimer's disease biomarkers in cognitively normal older adults

Objective: In addition to the increasingly recognized role of physical exercise in maintaining cognition, exercise may influence Alzheimer's disease (AD) pathology, as transgenic mouse studies show lowered levels of AD pathology in exercise groups. The objective of this study was to elucidate the association between exercise and AD pathology in humans using Pittsburgh compound-B (PIB), amyloid-β (Aβ)₄₂, tau, and phosphorylated tau (ptau) ₁₈₁ biomarkers. Methods: Sixty-nine older adults (17 males, 52 females) aged 55 to 88 years, were recruited and confirmed to be cognitively normal. A questionnaire on physical exercise levels over the past decade was administered to all. Cerebrospinal fluid samples were collected from 56 participants, and amyloid imaging with PIB was performed on 54 participants. Results: Participants were classified based on biomarker levels. Those with elevated PIB (p = 0.030), tau (p = 0.040), and ptau₁₈₁ (p = 0.044) had significantly lower exercise, with a nonsignificant trend for lower Aβ₄₂ (p = 0.135) to be associated with less exercise. Results were similar for PIB after controlling for covariates; tau (p = 0.115) and ptau₁₈₁ (p = 0.123) differences were reduced to nonsignificant trends. Additional analyses also demonstrated that active individuals who met the exercise guidelines set by the American Heart Association had significantly lower PIB binding and higher Aβ₄₂ levels with and without controlling for covariates (PIB: p = 0.006 and p = 0.001; Aβ₄₂: p = 0.042 and p = 0.046). Last, the associations between exercise engagement and PIB levels were more prominent in APOE epsilon 4 noncarriers. Interpretation: Collectively, these results are supportive of an association between exercise engagement and AD biomarkers in cognitively normal older adults.