Developmental conditions and adult socioeconomic context jointly shape cognitive aging through brain reserve.

OBJECTIVES: Cognitive aging shows substantial inter-individual heterogeneity, which may be shaped by both early-life developmental conditions and adult socioeconomic environments. However, how these life-course factors jointly relate to cognitive aging and the potential neuroanatomical correlates underlying these associations remain unclear. METHODS: Using data from 35,105 UK Biobank participants with birth weight information, comprehensive cognitive assessments, and brain MRI, we examined associations between early-life growth and domain-specific cognitive performance in mid- to late adulthood, tested interactions with adult socioeconomic status (SES), and evaluated regional gray matter structures as potential mediators. RESULTS: Low birth weight was associated with poorer performance in reasoning ability, memory, and executive function. Higher adult SES attenuated these associations, particularly for memory and executive functioning. Thalamic gray matter structure showed the strongest associations with cognitive performance and explained 17% to 44% of the association between birth weight and cognitive performance independent of adult SES. CONCLUSIONS: These findings suggest that higher adult socioeconomic resources may attenuate, but not fully offset, the adverse associations of early-life disadvantage, highlighting the importance of considering both early developmental conditions and adult social environments in understanding inequalities in cognitive aging.