https://www.selleckchem.com/ Results from longitudinal studies suggest that regular leisure time physical activity (LTPA) is associated with reduced risk of dementia or Alzheimer disease. Data on the association between LTPA and brain magnetic resonance imaging (MRI) measures remain scarce and inconsistent. To examine the association of LTPA and MRI-assessed brain aging measures in a multiethnic elderly population. This cross-sectional study included 1443 older (≥65 years) adults without dementia who were participants of the Washington/Hamilton Heights-Inwood Columbia Aging Project study. LTPA, from self-reported questionnaire, was calculated as metabolic equivalent of energy expenditure. Both moderate to vigorous LTPA, assessed as meeting Physical Activity Guidelines for Americans (≥150 minutes/week) or not, and light-intensity LTPA were also examined. LTPA. Primary outcomes included total brain volume (TBV), cortical thickness, and white matter hyperintensity volume, all derived from MRI scans with established methods and adj[SE], 9.03 [4.26] cm3; P = .03) compared with the nonactive group. Meeting Physical Activity Guidelines for Americans (TBV β [SE], 18.82 [5.14] cm3; P < .001) and light-intensity LTPA (TBV β [SE], 9.26 [4.29] cm3; P = .03) were also associated with larger brain measures. The association between LTPA and TBV was moderated by race/ethnicity, sex, and APOE status, but generally existed in all subgroups. The results remained similar after excluding participants with mild cognitive impairment. In this study, more physical activity was associated with larger brain volume in older adults. Longitudinal studies are warranted to explore the potential role of physical activity in brain health among older individuals. In this study, more physical activity was associated with larger brain volume in older adults. Longitudinal studies are warranted to explore the potential role of physical activity in brain health among older individuals. The optimal level o