| Insulin resistance is thought to be a common link underlying two of the leading causes of{09} morbidity and mortality in the elderly: type 2 diabetes mellitus(DM) and coronary heart disease. Insulin resistance is an independent risk factor for CHD in middle aged adults and one of the two cardinal defects in type 2 diabetes. beta-cell dysfunction, the other cardinal defect in diabetes, was once thought to be a less important predictor of DM than insulin resistance, which was considered the primary defect and the earliest marker of disease. beta-cell dysfunction is now thought to have an earlier and more central role in the deterioration of carbohydrate metabolism, particularly in the elderly. The relative roles of insulin resistance and beta-cell dysfunction in the elderly have been investigated in many physiological studies, but not in any large population based studies. Using the homeostasis model assessment method (HOMA)(1) we measured the effect of age on insulin resistance and compensatory beta-cell function as well as the risk of diabetes and coronary heart disease associated with insulin resistance and compensatory beta-cell function in the Cardiovascular Health Study, a large elderly cohort. We found that in cross-sectional data, insulin resistance increased with BMI, but not with age, even after adjustment for compensatory beta-cell function. Longitudinal analyses showed that adjusting for compensatory beta-cell function increased the predictive power of IR for both diabetes and coronary heart disease. IR and compensatory beta-cell function were the most important predictors of DM, but they were weak predictors of coronary heart disease after adjusting for traditional risk factors. |
