Value of Coronary Artery Calcium Scanning by Computed Tomography for Predicting Coronary Heart Disease in Diabetic Subjects

OBJECTIVE—The South Bay Heart Watch is a cohort study designed to determine the significance of coronary calcium in high-risk asymptomatic patients. This is a report of the relative risk (RR) for outcomes of coronary artery calcium in diabetic and nondiabetic subjects. RESEARCH DESIGN AND METHODS—A total of 1,312 diabetic and nondiabetic subjects underwent risk factor screening and computed tomography testing for coronary calcium at baseline and were followed clinically for 6.3 ± 1.4 years. End points were either 1) hard events of nonfatal myocardial infarction (MI) or coronary death or 2) any cardiovascular event (nonfatal MI, coronary death, coronary revascularization, or stroke). RESULTS—The incidence rates of a hard event and any cardiovascular event for diabetic and nondiabetic subjects were 14.5 and 6.1% and 23.8 and 12.2%, respectively (P 0.001). Cox regression analyses of the combined risk relationship of diabetes status and calcium score demonstrated that relative to nondiabetic subjects with low calcium scores (2.8), diabetic subjects with calcium scores ≥2.8 exhibited at least a fourfold increase in the risk of either a hard or any cardiovascular event (P 0.001). Cox regression analyses conducted separately for nondiabetic and diabetic subjects revealed that coronary calcium score risk groups were significantly associated with events in nondiabetic subjects (RR ≥ 2.6, P ≤ 0.01), but not in diabetic subjects (RR ≤ 1.7, P 0.05). CONCLUSIONS—The risk of coronary heart disease increases with increasing calcium scores and diabetes status. Calcium scores have less prognostic value in diabetic subjects.