Risk Profile and Prediction of Long-Term Ischemic Stroke Mortality

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Abstract
Background —Multinational comparisons demonstrate marked ethnic and regional variation in stroke mortality and risk-factor distribution. We assessed the role of ethnicity and estimated the cumulative effect of multiple risk factors on long-term ischemic stroke mortality. Methods and Results —Civil servants and municipal employees in Israel (n=9734 men; age, ≥42 years), chosen by stratified sampling in 6 prespecified areas of birth (those born in Israel and those who were immigrants from 5 other regional-ethnic strata), were included in the Israeli Ischemic Heart Disease (IIHD) Project. Over a 21-year follow-up period, age-adjusted mortality rates per 10 000 person-years attributed to ischemic stroke (n=282; International Classification of Diseases [ICD]-9 codes 433 to 438) were higher among immigrants to Israel from northern Africa and the Mideast (17.1 to 19.0), than from 3 parts of Europe (11.3 to 12.4). Crude rates per 1000 subjects observed in those born in Asia or Africa (29.4 to 31.2) exceeded rates predicted by risk-factor profiles (21.4 to 24.9). Adjusted hazard ratios were 3.00 for age (per 10 years), 2.15 for left ventricular hypertrophy, 1.69 for systolic blood pressure (BP, per 20 mm Hg), 1.86 for diabetes mellitus, 1.83 for peripheral vascular disease, 1.79 for smoking (>20 cigarettes per day), 1.51 for coronary heart disease, 1.16 for percent cholesterol contained in the HDL fraction (%HDL, per 5% decrease), and 1.88 for diastolic BP (per 12 mm Hg; assessed in an alternative model). Accounting for regression dilution bias and assessed from repeat measurements, we found that hazard ratio estimates associated with diastolic BP, systolic BP, and percent HDL (per increments described) increased to 3.22, 2.23, and 1.23, respectively. Ischemic stroke mortality rates were 30-fold greater among subjects at the highest versus the lowest quintile of predicted probability according to risk-factor profiles (81.2 versus 2.6 per 1000 subjects). Conclusions —Assessment of multiple risk factors provides useful quantitative prediction of long-term ischemic stroke mortality risk. Regional-ethnic variations are consistent with a hypothesis that other, undetermined inherent genetic or sociocultural factors act to increase ischemic stroke mortality rates in immigrants to Israel from the Mideast and northern Africa over that predicted by conventional risk factors.