Physical Activity and β-Amyloid Brain Levels in Humans: A Systematic Review

Physical activity (PA) contributes to brain health and plasticity, which suggests that PA would protect against the development of Alzheimer's disease (AD). However, research on PA and AD biomarkers is very scarce. The objective of the present study was to perform a systematic review of studies that investigated the associations between PA and β-amyloid brain deposition in humans. Electronic searches were performed in PubMed, Cochrane Library, SportDiscus, PEDro, and PsychInfo databases. Articles were eligible if they have assessed both PA and β-amyloid brain deposition in humans. Five articles, published between 2010 and 2013, met eligibility criteria (study population varied across studies from 54 to 515, according with the β-amyloid measure. All five studies assessed both PA and PET-amyloid; among them, two studies also assessed CSF Aβ42 levels). All studies were based on cross-sectional data, from non-demented populations. Among the five included studies, three found significant associations between PA and β-amyloid brain deposition, and the other two did not find any significant association; limited evidence suggests that PA-amyloid plaques associations would be APOE ε4 allele-specific. In sum, no solid conclusions can be drawn on the associations between PA and human β-amyloid brain deposition currently. Future research on this topic should particularly pay attention to the operationalisation of clinically relevant and valid PA variables and should include important confounders in multivariate analysis. More information is needed on the potential interactions between PA and other AD risk factors (e.g., cognitive activities, APOE ε4 status, nutrition, smoking) and their combined effects on AD biomarkers.