Ankle-brachial index and 7-year ischemic stroke incidence - The ARIC study

Background and Purpose-Low ankle-brachial index (ABI), which is the ratio o f tibial artery systolic blood pressure to brachial systolic artery pressur e, is known to be a measure of lower limb peripheral artery disease as well as a marker for other cardiovascular disease events. The ability of ABI to predict incident ischemic stroke, however, is not established in populatio n-based studies. Methods-ABI was measured in a cohort of 14 839 black and white men and wome n aged 45 to 64 years. Stroke incidence was calculated during approximately 7 years of follow-up. Results-A total of 206 incident strokes occurred. Adjusted stroke incidence rates were markedly higher for those in the lowest versus the highest cate gories of ABI for men, women, blacks, and whites. The proportional hazards regression model, adjusted for age, race, gender, and field center, showed an inverse linear trend between ABI and ischemic stroke incidence (P <0.000 1). The lowest group (ABI < 0.80) had a hazard ratio of 5.68 (95% CI 2.77 t o 11.66). After adjustment for major risk factors in a multivariate model, the hazard ratio in the lowest group was elevated (1.93) but no longer stat istically significant (95% Cl 0.78 to 4.78). There was, however, still an i ndication of an overall inverse linear trend between ABI and incident strok e (P=0.03). Conclusions-Low ABI was strongly associated with increased incidence of isc hemic stroke, but the relationship was substantially reduced after adjustme nt for major cardiovascular risk factors.