Self-Reported Race as a Social Determinant of Stroke Risk in Observational Versus Clinical Trial Datasets

Self-reported Black (SRB) Americans are approximately twice as likely to have a stroke as self-reported White (SRW) Americans. While social determinants of health and vascular risk factors account for some of the disparity, half the increased risk remains unexplained and may be related to unmeasured real-world factors of the racialized experience.

and Methods In this cohort study, we compared SRB and SRW participants in the Systolic Blood Pressure Intervention Trial (SPRINT) to the same groups in the observational Atherosclerosis Risk in Communities (ARIC) study to evaluate if clinical trial participation mitigates disparities in stroke risk. We set the ARIC baseline at visit 4 and excluded participants with prior stroke to create an ARIC cohort similar in age to SPRINT participants. The study outcome was incident primary stroke. We report hazard ratios from Cox models and inverse-probability weighted Cox models with propensity score matching on participant age, sex, diabetes, atrial fibrillation, and smoking.

We included 10,094 patients from ARIC and 8,869 from SPRINT, of which 26.1% were SRB. The risk of stroke between SRW participants in SPRINT versus ARIC was not significantly different (IPW-Weighted HR 0.78 [0.52-1.19]). SRB ARIC participants were twice as likely to have a stroke as SRW ARIC participants (IPW-Weighted HR = 1.96 [1.41-2.71]). However, SRB SPRINT participants did not have higher stroke risk compared to SRW SPRINT or ARIC participants (IPW-Weighted HR 0.99 [0.68--1.77] and 0.95 [.57-1.59], respectively). SRB SPRINT participants in the intensive BP control group had a lower risk of stroke compared to SRB ARIC participants (IPW-Weighted HR = 0.39 [0.20-0.75]).

SRB race, compared to SRW race, is associated with an increase in primary stroke risk in the ARIC study but not in the SPRINT trial. The absence of the racial disparity in stroke incidence in SPRINT indicates that aspects of the disparity are modifiable. Population-based interventions that test this hypothesis deserve further attention.