Insulin sensitivity, proinsulin and insulin as predictors of coronary heart disease. A population-based 10-year, follow-up study in 70-year old men using the euglycaemic insulin clamp.

AIMS/HYPOTHESIS: The association between CHD and insulin sensitivity (Si) measured by the euglycaemic insulin clamp has not been examined previously. Earlier studies found a relationship between CHD and elevated plasma insulin, an analysis that may have been confounded by co-determination of proinsulin, which has evolved as a stronger predictor of CHD. The aim was to determine the longitudinal relationships between Si, intact proinsulin, 32-33 split proinsulin, specific insulin and subsequent CHD.
METHODS: This was a population-based cohort study of 815 men in Uppsala, Sweden, aged 70 years at baseline with a follow-up of up to 10 years. Baseline insulin sensitivity was determined by euglycaemic insulin clamp. Fasting proinsulin, 32-33 split proinsulin and specific insulin concentrations were analysed using specific two-site immunometric assays. CHD was taken as diagnosed, if stated (in the event of death) on the Cause of Death Registry, or for subjects hospitalised for the first time with CHD, if CHD was recorded in the Hospital-Discharge Registry. The associations were analysed using Cox's proportional hazards, presented as hazard ratios (HRs) with their 95% CIs for a one-SD increase in the predictor.
RESULTS: In multivariate analysis, Si (HR:0.80, CI:0.65-0.97) adjusted for serum cholesterol, systolic blood pressure, fasting plasma glucose, BMI and smoking predicted CHD. Intact proinsulin (HR:1.18, CI:1.01-1.38), adjusted as the model above, predicted CHD, whereas 32-33 split proinsulin (HR:1.13, CI:0.95-1.35) or specific insulin (HR:1.07, CI:0.89-1.30) did not. CONCLUSIONS/
INTERPRETATION: Insulin resistance measured by the euglycaemic insulin clamp predicts subsequent CHD in elderly men. Proinsulin provides a better prediction of CHD than insulin.