The Inclusion of Stroke in Risk Stratification for Primary Prevention of Vascular Events

Abstract

The Framingham coronary heart disease (CHD) risk score estimates 10-year risk of myocardial infarction (MI) and CHD death. Because preventive approaches to CHD and stroke are similar, a composite outcome may be more appropriate. We compared 10-year risk of (1) MI or CHD death; and (2) stroke, MI, or CHD death among individuals free of vascular disease. The Northern Manhattan Study contains a prospective, population-based study of stroke- and CHD-free individuals ≥40 years of age followed for a median of 10 years for vascular events. Framingham coronary heart disease risk score was calculated for each individual and for each category of predicted risk, Kaplan–Meier observed 10-year cumulative probabilities were calculated for (1) MI or CHD death; and (2) stroke, MI, or CHD death. The cumulative probability of (1) was subtracted from (2), and 95% CIs for the difference were obtained with 1000 bootstrap samples. Using stratified analyses by race–ethnicity, we compared risk differences among race–ethnic groups. Among 2613 participants (53% Hispanic, 25% non-Hispanic black, and 20% non-Hispanic white), observed 10-year risk of MI or CHD death was 14.20%. With stroke in the outcome, observed risk was 21.98% (absolute risk difference, 7.78%; 95% CI, 5.86% to 9.75%). The absolute risk difference among blacks was significantly larger than among whites ( P =0.01). In this multiethnic urban population, adding stroke to the risk stratification outcome cluster resulted in a 55% relative increase in estimated risk and crossing of the absolute risk threshold (>20% over 10 years) considered for preventive treatments such as statins.