Introduction: Hypertension (HTN), particularly untreated HTN, has been found to be a significant risk factor for ICH in predominately white ICH populations. We evaluated the risk of treated and untreated HTN on ICH in a multi-ethnic case-control study.
Hypothesis: Treated and untreated HTN confer variable risk for ICH by race/ethnicity.
Methods: The Ethnic/Racial Variations of ICH (ERICH) study is a prospective, multicenter, case-control study of ICH among whites, blacks, and Hispanics. Cases were enrolled from 42 recruitment centers using hot-pursuit. Controls matched to cases 1:1 by age (±5 years), sex, race/ethnicity, and metropolitan area were recruited by random-digit dialing. Subjects were interviewed to determine whether they had a history of HTN and if they took medications to reduce blood pressure.
Results: Between 9/2010 and 6/2015, 891 white, 833 black, and 599 Hispanic case/control pairs were enrolled. Higher proportions of black and Hispanic ICH with HTN were untreated, compared with whites (43.3% and 48.3% vs. 33.2%; p=.0002 and p<.0001, respectively). When adjusted for medical insurance status, a significant difference persisted for whites vs. Hispanics (p=.002), but not whites vs. blacks (p=.197). In multivariate analyses adjusted for alcohol use, anticoagulation, hypercholesterolemia, education, and insurance status, treated HTN was a significant risk factor for ICH in whites (OR=1.72, 95% CI 1.33-2.22, p<.0001), blacks (3.04, 2.13-4.34, <.0001), and Hispanics (2.57, 1.64-4.00, <.0001). Untreated HTN was a substantially greater risk factor for ICH for all three racial/ethnic groups: whites (9.53, 5.88-15.45, <.0001), blacks (11.10, 7.06-17.47, <.0001), Hispanics (9.65, 5.49-16.95, <.0001). In the subtype analyses of deep, lobar, and infratentorial ICH, untreated HTN resulted in ORs of 3.50 to 24.81, with statistical significance for all subtypes and ethnic groups.
Conclusion: Treatment of HTN reduces the risk of ICH conferred by HTN markedly, but not completely. Untreated hypertension, which is significantly more prevalent among black and Hispanic ICH cases than among white cases, confers at least a 9-fold risk of ICH regardless of race. Treatment of hypertension is expected to have substantial impact on risk of ICH.