Abstract
IMPORTANCE: Socioeconomic status (SES) has an important association with cognitive function and structural brain indices. Identifying the nature of this association will guide strategies for improving health equity. OBJECTIVE: To test the longitudinal associations of SES with cognitive decline and brain characteristics and to examine whether these associations differ between Black and White individuals. DESIGN, SETTING, AND PARTICIPANTS: Participants aged 65 years old or older were recruited for this population-based cohort study from 4 communities on the south side of Chicago, Illinois. At-home interviews were conducted between 1993 and 2012. The data were analyzed in April 2024. MAIN OUTCOMES AND MEASURES: Outcome measures were level and change in global cognition and 4 individual tests. Three magnetic resonance imaging (MRI) measures of the brain included total brain volume, hippocampal volumes, and white matter hyperintensities (WMH). Childhood SES was assessed using parental education levels, father's occupation, and childhood finance rating. Adulthood SES was assessed using the participants' education, occupation, and income. Lifetime SES was assessed on the basis of the mother's education, childhood SES, and participants' occupation and income. RESULTS: Of the 7303 participants (mean [SD] age, 72.3 [6.3] years; 4573 female participants [63%]), 4581 (63%) were non-Hispanic Black, and 2722 (37%) were non-Hispanic White. SES was higher for White individuals compared with Black individuals in childhood, adulthood, and across the lifespan. Higher lifetime SES was associated with better global cognitive functioning at baseline (estimate, 0.337; 95% CI, 0.317 to 0.357; P < .001) but not with decline over time (estimate, 0.003; 95% CI, -0.001 to 0.006; P = .10). Higher lifetime SES was associated with a better baseline score on the Mini-Mental State Examination (estimate, 0.281; 95% CI, 0.261 to 0.302; P < .001) and a slower decline for all participants (estimate, 0.012; 95% CI, 0.008 to 0.016; P < .001). In a subset of 933 participants who underwent MRI, there was an association between lifetime SES and healthier brain structures, as measured by total brain volume (estimate, 3.18; 95% CI, 0.20 to 6.17; P = .04) and WMH burden (estimate, -0.11; 95% CI, -0.21 to -0.01; P = .03). CONCLUSIONS AND RELEVANCE: In this cohort study, SES, mainly in adulthood, was associated with a person's cognitive status and brain structure, resulting in a discrepancy in cognitive status over time. These findings point to a need for interventions that improve SES throughout the lifespan, particularly for Black individuals, who had lower SES than White individuals.