Abstract 38: Racial Differences in Intracerebral Hemorrhage Risk: The REasons for Geographic and Racial Differences in Stroke Study (REGARDS)

Abstract

Introduction: Intracerebral Hemorrhage (ICH) risk is higher in blacks vs whites in the U.S. especially at younger ages. We used the REGARDS study to determine what prospectively assessed factors may underlie black-white differences in ICH risk. Methods: REGARDS recruited black and white individuals aged 45+ in the U.S. to explain regional and racial differences in stroke risk. Cox models with an age*race interaction term estimated the age-dependent hazard ratio (HR) of black versus white individuals for ICH. The 95% confidence interval (CI) of the percent attenuation of the age-dependent hazard ratio (HR) from the baseline to the final model was calculated using bootstrapping. Results: Among 29,694 REGARDS participants (55% women; 41% black), 160 ICH events occurred over 254,440 person-years of follow-up (median 9.5 years). The point estimate for the black-white HR for ICH decreased with increasing age, being 4.8, 2.7, and 1.5 at ages 45y, 55y, and 65y (Table, Baseline Model). In a final model, the point estimate for ages 45, 55, and 65 decreased to 3.9, 2.3, and 1.4, corresponding to a 24% (95% CI 11%. 100%), 24% (95% CI 16%, 100%), and 20% (95% CI 14%, 100%) decrease in the HR at ages 45y, 55y, and 65y. No increased ICH risk was seen in blacks over 65y. When added individually to the baseline model, none of the risk factors except diet (modeled as 6 principle components of dietary patterns) attenuated the association of black race with ICH risk. Conclusions: A quarter of the association of race with ICH may be explained by the risk factors studied here. Diet, particularly salt intake, may play a large role in black-white differences of ICH risk. While the absolute number of ICH events limits our analysis, prospective assessment of risk factors is a huge strength. Future primary and secondary ICH prevention efforts, particularly in younger blacks, should assess efficacy of dietary interventions.