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 angiographed coronary patients.