Local Wealth Inequality and Working-Age Mortality in US Counties

Importance: Household wealth is associated with health and survival, but little is known about whether wealth inequality is associated with mortality as a contextual exposure. Objective: To examine the association between local wealth inequality and age-adjusted all-cause mortality across US counties over 5 decades. Design, Setting, and Participants: This longitudinal, county-level study of up to 18 344 county-year observations from 1970 to 2019 linked restricted-access, all-cause mortality data from the US National Center for Health Statistics with county-level population and sociodemographic information and commuting zone estimates of household wealth inequality from the GEOWEALTH-US database. US counties were observed at decennial intervals from 1970 to 2019, with 2019 mortality used for the final period to avoid distortion from the COVID-19 pandemic. After listwise deletion, the estimation sample included up to 18 344 county-year observations nested in 732 commuting zones. Exposure: Commuting zone Gini index score of household net wealth inequality. Main Outcomes and Measures: County-specific, sex-specific, age-adjusted all-cause mortality rates for ages 25 to 44, 45 to 54, and 55 to 64 years, modeled on the natural log scale. Results: In adjusted 2-way fixed-effects models with county, year, and state by year fixed effects, higher local wealth inequality was associated with higher mortality across all sex-age groups. Unstandardized regression coefficients (b) were 1.72 (95% CI, 0.99-2.45), 1.57 (95% CI, 0.96-2.18), and 1.11 (95% CI, 0.65-1.57) for female individuals aged 25 to 44, 45 to 54, and 55 to 64 years, respectively, and 0.75 (95% CI, 0.12-1.37), 0.71 (95% CI, 0.27-1.14), and 0.66 (95% CI, 0.24-1.08), respectively, for male individuals in the same age groups. Conclusions and Relevance: In this aggregate longitudinal cross-sectional study, increases in local wealth inequality were associated with within-county increases in working-age mortality. These findings suggest that wealth inequality may be relevant to population health beyond income inequality, although mechanisms and causality require further study.