Objective: The aim of this study was to evaluate whether low insulin sensitivity (Si) measured using a modified frequently sampled intravenous glucose tolerance test with minimal model analysis is associated with coronary artery disease (CAD) independent of other cardiovascular risk factors.
Research design and methods: We studied 1,482 women and men, age 40-69 years old, African American (28%), Hispanic (34%), or non-Hispanic white (38%), with normal (45%), impaired (23%), or diabetic (32%) glucose tolerance. CAD defined as confirmed past myocardial infarction, coronary artery bypass graft, coronary angioplasty, or presence of a major Q-wave was found in 91 participants.
Results: The odds ratio (OR) for CAD was greatest among individuals in the two lowest quintiles of Si (2.4, 95% CI 1.0-5.6 and 4.7, 2.1-10.7) compared with the highest Si quintile. After adjusting for demographic and cardiovascular risk factors, a decrement from the 75th to 25th percentile in Si was associated with a 56% increase in CAD (P=0.028). Similar increments in fasting or 2-h insulin levels were associated with, respectively, only 15 (NS) and 3% (NS) increases in CAD. The association between Si and CAD was partially mediated by insulin, HDL cholesterol and triglyceride levels, hypertension, diabetes, and obesity, but not LDL cholesterol or cigarette smoking.
Conclusions: Low Si is associated with CAD independently of and stronger than plasma insulin levels. Part of the association is accounted for by dyslipidemia, hypertension, diabetes, and obesity.