Risk-Factor Clustering and Cardiovascular Disease Risk in Hypertensive Patients

BACKGROUND: Patients with hypertension often have other major risk factors for cardiovascular disease (CVD). Little is known, however, about the extent of risk-factor clustering in these patients and its importance in CVD risk and medical-care costs. METHODS: Study subjects were selected from the electronic medical records system of Kaiser Permanente Northwest, a large health maintenance organization, and included all patients aged > or =35 years with hypertension who were free of CVD in 1998. Subjects were stratified into eight risk-factor clusters based on whether or not they also had diabetes, hyperlipidemia, or a high body mass index (BMI). The risk of cardiovascular events was examined in each cluster over 6 years beginning January 1, 1999, using Kaplan-Meier methods and Cox proportional hazards models. Cumulative total medical-care costs (per patient) over 6 years also were examined. RESULTS: A total of 57,573 patients with hypertension who were free of CVD in 1998 were identified; 56% of subjects also had diabetes, hyperlipidemia, or high BMI. In analyses controlling for age, sex, and smoking status, the relative risk of cardiovascular events over 6 years was highest for patients with comorbid diabetes, ranging from 2.07 (95% confidence interval, 1.86-2.30) for those with diabetes only to 2.80 (95% confidence interval, 2.48-3.17) for those with diabetes, hyperlipidemia, and high BMI. Cumulative medical-care costs generally increased with additional risk factors. Comorbid diabetes had the greatest impact on costs over 6 years. CONCLUSIONS: More than 50% of patients with hypertension also had diabetes, hyperlipidemia, or high BMI. Patients with these additional risk factors (especially diabetes) had a substantially higher CVD risk and medical-care costs.