Background--Both the metabolic syndrome and an increased apolipoprotein B/AI (apoB/AI) ratio are powerful risk factors for cardiovascular events. We hypothesized that the apoB/AI ratio well-characterizes the dyslipidemia associated with insulin resistance and the metabolic syndrome and investigated those relations and if the apoB/AI ratio and the metabolic syndrome independently predicted subsequent myocardial infarction (MI).

Methods and Results--A community-based sample of 2322 men aged 50 was investigated at baseline and again at age 70. ApoB/AI ratio and the metabolic syndrome (National Cholesterol Education Program definition) were evaluated, and the incidence of fatal and nonfatal MI was followed for a median of 26.8 years from the age 50 baseline. ApoB/AI ratio was significantly higher in men with versus without the metabolic syndrome (P<0.0001), and increased with the number of components defining the syndrome (P<0.0001). ApoB/AI ratio was inversely related to euglycemic insulin clamp glucose disposal rate at age 70 (r=-0.34, P<0.0001). During follow-up from age 50, 462 subjects developed an MI. An apoB/AI ratio>=0.9 (hazard ratio [HR], 1.48; 95% confidence interval [CI], 1.15 to 1.91) and presence of the metabolic syndrome (HR, 1.69; 95% CI, 1.30 to 2.21) at baseline were independent predictors for MI, adjusting for low-density lipoprotein cholesterol and smoking.

Conclusion--The apoB/AI ratio was related to the metabolic syndrome, as well as to a direct measurement of insulin resistance. Despite this, the apoB/AI ratio and the metabolic syndrome were both independent long-term predictors of MI in a community-based sample of middle-aged men.