Social Determinants of Health Attenuate the Relationship Between Race and Ethnicity and White Matter Hyperintensity Severity but not Microbleed Presence in Patients with Intracerebral Hemorrhage

Background The association between race and ethnicity and microvascular disease in patients with intracerebral hemorrhage (ICH) is unclear. We hypothesized that social determinants of health (SDOHs) mediate the relationship between race and ethnicity and severity of white matter hyperintensities (WMHs) and microbleeds in patients with ICH. Methods We performed a retrospective observational cohort study of patients with ICH at two tertiary care hospitals between 2013 and 2020 who underwent magnetic resonance imaging of the brain. Magnetic resonance imaging scans were evaluated for the presence of microbleeds and WMH severity (defined by the Fazekas scale; moderate to severe WMH defined as Fazekas scores 3-6). We assessed for associations between sex, race and ethnicity, employment status, median household income, education level, insurance status, and imaging biomarkers of microvascular disease. A mediation analysis was used to investigate the influence of SDOHs on the associations between race and imaging features. We assessed the relationship of all variables with discharge outcomes. Results We identified 233 patients (mean age 62 [SD 16]; 48% female) with ICH. Of these, 19% were Black non-Hispanic, 32% had a high school education or less, 21% required an interpreter, 11% were unemployed, and 6% were uninsured. Moderate to severe WMH, identified in 114 (50%) patients, was associated with age, Black non-Hispanic race and ethnicity, highest level of education, insurance status, and history of hypertension, hyperlipidemia, or diabetes (p < 0.05). In the mediation analysis, the proportion of the association between Black non-Hispanic race and ethnicity and the Fazekas score that was mediated by highest level of education was 65%. Microbleeds, present in 130 (57%) patients, was associated with age, highest level of education, and history of diabetes or hypertension (p < 0.05). Age, highest level of education, insurance status, and employment status were associated with discharge modified Rankin Scale scores of 3-6, but race and ethnicity was not. Conclusions The association between Black non-Hispanic race and ethnicity and moderate to severe WMH lost significance after we adjusted for highest level of education, suggesting that SDOHs may mediate the association between race and ethnicity and microvascular disease.