Abstract 14: Associations Between Measures of Structural Racism and Acute Ischemic Stroke Incidence in the US

Abstract

Introduction: Racial differences in socioeconomic characteristics are believed to be secondary to structural racism. While socioeconomic factors explain some of the racial disparity in stroke incidence at an individual level, little is known about the association between societal-level structural racism and the incidence of acute ischemic stroke (AIS). Methods: We conducted a national cross-sectional analysis of 71,078,619 adults aged >65 years enrolled in Medicare from January 1, 2016 to December 31, 2019. The primary exposure was a county-level composite structural racism score that was calculated from constituent measures of structural racism: segregation indices (delta index, dissimilarity index, isolation index), Gini index, housing discrimination, educational attainment ratio, employment ratio, income ratio. The primary outcome was AIS incidence. Results: The composite structural racism score identified significant geographic variation in structural racism across the U.S. (mean 0.818, SD 2.874, IQR 3.02). Among 844,406 Medicare beneficiaries with incident AIS, Black individuals had a 19% increased hazard of AIS compared to White individuals (HR 1.19, 95% CI 1.14-1.25, p<0.0001). Increasing segregation conferred increased incidence of AIS for both Black and White populations. Each standard deviation increase in the composite structural racism score was associated with an 18% increased incidence in AIS (HR 1.18, 95% CI 1.12-1.24) in the total population. This association interacted with race (p=0.03), with a greater magnitude of association for White (HR 1.19, 95% CI 1.13-1.25, p<0.0001) versus Black (HR 1.09 ,95% CI 1.03-1.16, p=0.0073) individuals. Conclusions: There is significant geographic variation in structural racism at the county level across the US, and increasing levels of structural racism are associated with increased incidence of AIS, regardless of race.