Inverse association of serum cholesterol with plasma insulin in the elderly. Cross-sectional and prospective analyses

Cross-sectional studies have suggested that high plasma insulin is associated with relatively low levels of low density lipoprotein (LDL)-cholesterol. The present study was aimed at re-testing this association in a 70-year-old age cohort (N = 1023), and testing whether it could be caused by excessive mortality of hyperinsulinemic subjects with high LDL-cholesterol. A reverse U-shaped association between LDL-cholesterol and fasting plasma insulin was confirmed. LDL-cholesterol, HDL-cholesterol and total cholesterol were lowest in the highest insulin quarter. These associations remained after adjustment for diabetes, obesity and general health status. The combination of high LDL-cholesterol (> 4.25 mmol/L, 75th percentile) and high insulin (> 10 IU/L, 50th percentile) was not associated with excess 5-year mortality in this age cohort. Nor was it associated with excess mortality in four other elderly age cohorts (N = 1188), in which similar associations of cholesterol and insulin have been demonstrated. Thus, the inverse association of LDL-cholesterol with fasting insulin in the elderly is not caused by selective over mortality.