Late-Life Physical Activities Moderate the Relationship of Amyloid-β Pathology with Neurodegeneration in Individuals Without Dementia.

BACKGROUND: Physical activities (PA) have been suggested to reduce the risk of Alzheimer's disease (AD) dementia. However, information on the neuropathological links underlying the relationship is limited.
OBJECTIVE: We investigated the role of midlife and late-life PA with in vivo AD neuropathologies in old adults without dementia.
METHODS: This study included participants from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer's disease (KBASE). The participants underwent comprehensive clinical and neuropsychological assessment, [11C] Pittsburgh Compound B positron emission tomography (PET), [18F] fluorodeoxyglucose PET, and magnetic resonance imaging. Using the multi-modal brain imaging data, in vivo AD pathologies including global amyloid deposition, AD-signature region cerebral glucose metabolism (AD-CM), and AD-signature region cortical thickness (AD-CT) were quantified. Both midlife and late-life PA of participants were measured using the Lifetime Total Physical Activity Questionnaire.
RESULTS: This study was performed on 260 participants without dementia (195 with normal cognitive function and 65 with mild cognitive impairment). PA of neither midlife nor late-life showed direct correspondence with any neuroimaging biomarker. However, late-life PA moderated the relationship of brain amyloid-β (Aβ) deposition with AD-CM and AD-CT. Aβ positivity had a significant negative effect on both AD-CM and AD-CT in individuals with lower late-life PA, but those with higher late-life PA did not show such results. Midlife PA did not have such a moderation effect.
CONCLUSION: The findings suggest that physically active lifestyle in late-life, rather than that in midlife, may delay AD-associated cognitive decline by decreasing Aβ-induced neurodegenerative changes in old adults.