Warfarin therapy reduced ischemic stroke risk in white patients with atrial fibrillation (RR 0.79; 95% CI 0.68-0.90) but did not show a statistically significant reduction in nonwhite patients.
Cohort (n=18,867)
Does warfarin reduce ischemic stroke in nonwhite patients with atrial fibrillation?
While warfarin significantly reduces ischemic stroke in white patients with atrial fibrillation, a statistically significant reduction was not observed in nonwhite patients, though this may be limited by sample size.
BACKGROUND AND PURPOSE: Warfarin reduces stroke risk in studies of predominantly white patients with atrial fibrillation (AF). Whether nonwhites also have lower rates of stroke while treated with warfarin is unclear. METHODS: A multiethnic stroke-free cohort hospitalized with nonrheumatic AF was identified in a large health maintenance organization. Stroke risk factors (advanced age, diabetes, hypertension, and heart failure), warfarin use, and anticoagulation intensity were assessed. Crude ischemic stroke rates were calculated by Poisson regression for each group while using and not using warfarin. Cox proportional hazard models were constructed to assess the independent effect of race/ethnicity on ischemic stroke. RESULTS: Between 1995 and 2000, we identified 18867 AF hospitalizations (78.5% white, 8% black, 9.5% Hispanic, and 3.9% Asian). Over the course of 63204 person-years follow-up (median, 3.3 years), 1226 ischemic strokes were identified. The percent-time on warfarin did not differ by race/ethnicity. The median percent-time on warfarin that international normalized ratio was 2 to 3 was 54.5% overall, but it was lower in blacks at 47.8%, whereas the other groups had a rate of approximately 54%. The rate ratios (95% CI) of ischemic stroke with warfarin compared to without warfarin for whites, blacks, Hispanics, and Asians were 0.79 (0.68 to 0.90), 0.92 (0.65 to 1.30), 0.71 (0.48 to 1.05), and 0.65 (0.34 to 1.23), respectively. CONCLUSIONS: In this cohort, we did not observe a statistically significant lower rate of stroke with warfarin therapy among nonwhites (in particular blacks) with previous AF hospitalizations. The relatively small numbers of nonwhites renders our estimates less than precise and should be interpreted with caution.
Shen et al. (Fri,) conducted a cohort in Atrial Fibrillation (n=18,867). Warfarin vs. No warfarin was evaluated on Ischemic stroke. Warfarin therapy reduced ischemic stroke risk in white patients with atrial fibrillation (RR 0.79; 95% CI 0.68-0.90) but did not show a statistically significant reduction in nonwhite patients.