The metabolic syndrome, insulin resistance, and cardiovascular risk in diabetic and nondiabetic patients

Context: The contribution of insulin resistance per se to the vascular risk conferred by the metabolic syndrome (MetS) is not known; conversely, it is uncertain whether insulin resistance confers vascular risk beyond the entity of the MetS. Objective: The objective of this study was to investigate the impact of the MetS ( Adult Treatment Panel III criteria) and insulin resistance ( as estimated by the homeostasis model assessment index) on the incidence of vascular events. Design and Patients: This was a prospective cohort study enrolling 750 consecutive patients undergoing coronary angiography for the evaluation of coronary artery disease. Setting: The study was performed at a tertiary care clinical research center. Main Outcome Measure: The main outcome measure was the incidence of vascular events over 2.3 yr. Results: Both the MetS and insulin resistance predicted vascular events after controlling for non-MetS risk factors [ hazard ratio (HR), 2.74 (95% confidence interval, 1.71-4.39; P < 0.001) and 1.51 (1.24-1.84; P < 0.001), respectively]. After additional adjustment for insulin resistance, the MetS remained significantly predictive of vascular events [ HR, 2.69 (1.57 - 4.64); P < 0.001], and conversely, insulin resistance remained significantly predictive of vascular events despite adjustment for the MetS [ standardized HR, 1.41 (1.14-1.75); P = 0.002]. Additional adjustment for the presence of type 2 diabetes revealed that both the MetS [ adjusted HR, 2.57 (1.47-4.51); P < 0.001] and homeostasis model assessment of insulin resistance [ standardized adjusted HR, 1.37 (1.09-1.73); P = 0.007] significantly predicted vascular events independent from diabetes status. Conclusions: Both the MetS and insulin resistance are strong and mutually independent predictors of vascular risk among angio-graphed coronary patients.