OBJECTIVE— To assess the magnitude of the association between the National Cholesterol Education Program’s Third Adult Treatment Panel Report (ATP III) definition of the metabolic syndrome and cardiovascular disease (CVD).

RESEARCH DESIGN AND METHODS— Cox regression was used to estimate the relative risk of incident coronary heart disease (CHD) and stroke among 12,089 black and white middle-aged individuals in the Atherosclerosis Risk in Communities (ARIC) study.

RESULTS— The metabolic syndrome was present in ∼23% of individuals without diabetes or prevalent CVD at baseline. Over an average of 11 years of follow-up, 879 incident CHD and 216 ischemic stroke events occurred. Among the components of the metabolic syndrome, elevated blood pressure and low levels of HDL cholesterol exhibited the strongest associations with CHD. Men and women with the metabolic syndrome were ∼1.5 and 2 times more likely to develop CHD than control subjects after adjustment for age, smoking, LDL cholesterol, and race/ARIC center (sex interaction P < 0.03). Similar associations were found between the metabolic syndrome and incident ischemic stroke. Comparison of receiver operating characteristic curves indicated that the metabolic syndrome did not materially improve CHD risk prediction beyond the level achieved by the Framingham Risk Score (FRS).

CONCLUSIONS— Individuals without diabetes or CVD, but with the metabolic syndrome, were at increased risk for long-term cardiovascular outcomes, although statistical models suggested that most of that risk was accounted for by the FRS. Nevertheless, identification of individuals with the metabolic syndrome may provide opportunities to intervene earlier in the development of shared disease pathways that predispose individuals to both CVD and diabetes.