Phoebe ImmsNikhil N. ChaudhariDaniel K. CummingsDaniel Eid RodríguezGiuseppe BarisanoPaul L. HooperM. Katherine SayreEdmond SeabrightRandall C. ThompsonM. Linda Sutherland2026-03-222026-03-22202510.1093/gerona/glaf163https://doi.org/10.1093/gerona/glaf163https://andeanlibrary.org/handle/123456789/77447Among Tsimane males, who are more physically active than Tsimane females, the association between age and cognition via BV is significantly mediated by physical activity. Among Tsimane females, mediation occurs directly via physical activity, bypassing BV. These results suggest that mechanisms of cognitive differences across ages differ by sex and population. Studying the relationship between brain atrophy and lifestyle in nonindustrialized populations elucidates biological and environmental correlates of brain health.enDemographyCognitionMediationPhysical activityPopulationPsychologyGerontologyMedicinearticle