County Racial Composition and Diminished Associations of Education With Mortality Across Causes

Abstract Background Educational attainment is associated with lower mortality, but the health advantages associated with education may depend on social context. Minorities’ Diminished Returns theory provides a framework for examining whether educational resources have weaker associations with population health in counties with higher percentages of Black residents. Methods We conducted a repeated county ecological study linking CDC WONDER mortality exports for 2018–2024 with American Community Survey five-year estimates. Outcomes were all-cause mortality, suicide (X60–X84), endocrine, nutritional, and metabolic mortality (E00–E88), and neoplasm mortality (C00–D48). Poisson mean models included population offsets, state and year fixed effects, county-clustered uncertainty, five socioeconomic indicators, racial and ethnic composition, and interactions between each socioeconomic indicator and county percent Black. Education was scaled per 10-percentage-point increase in bachelor’s-degree attainment. Results Samples included 21,708 county-years in 3,118 counties for all-cause mortality, 6,807 in 1,193 counties for suicide, 14,383 in 2,332 counties for metabolic mortality, and 20,135 in 2,961 counties for neoplasms. Education tended to have weaker inverse associations with mortality at higher county percent Black. Per 10-percentage-point higher percent Black, the ratio of education rate ratios was 1.016 for suicide (95% CI, 1.004–1.028; P=.011), 1.019 for metabolic mortality (95% CI, 1.0003–1.038; P=.047), and 1.011 for neoplasms (95% CI, 1.002–1.020; P=.021). The all-cause interaction was marginal (ratio, 1.008; 95% CI, 0.9997–1.017; P=.058). At 5% versus 25% Black, higher educational attainment was associated with approximately 9.3% versus 6.4% lower suicide mortality, 13.1% versus 9.8% lower metabolic mortality, and 10.0% versus 8.1% lower neoplasm mortality. Conclusions Linear interaction models suggested an MDR-like contextual pattern for education across several mortality outcomes, with a marginal association for all-cause mortality. These exploratory ecological findings warrant replication with age-standardized outcomes and direct measures of structural conditions.