[Glucose tolerance and insulin resistance in the elderly]

Glucose tolerance is reported to be impaired in the elderly, and this is said to be mainly due to a decrease in insulin sensitivity (insulin resistance). Insulin resistance is known to be associated with atherosclerosis and coronary artery disease. To clarify whether or not age-dependent changes in glucose tolerance and insulin sensitivity are risk factors for coronary artery disease, as they are in the case of the insulin resistance syndrome, we studied age-dependent changes in glucose tolerance, insulin sensitivity, blood pressure, and serum lipids in a large number of subjects who underwent annual health check-ups, and then studied the relationships between coronary artery disease and aging, insulin sensitivity, and other risk factors in subjects who underwent coronary angiography. Aging was associated with an increased prevalence of noninsulin-dependent diabetes mellitus and impaired glucose tolerance; even in subjects with normal glucose tolerance, plasma glucose levels during an oral glucose tolerance test were significantly higher in the elderly. Insulin sensitivity, as assessed by the ratio of the sum of the plasma glucose divided by the sum of the serum insulin during the test (sigma PG/sigma IRI), was significantly lower in subjects over 60 years old than in younger subjects. Age-dependent impairment of insulin sensitivity and glucose tolerance was associated with increased blood pressure and serum cholesterol levels, but not with changes in boy mass index or serum triglyceride levels. As an independent variable, aging, but not insulin sensitivity, was related to the severity of coronary artery disease. These data suggest that aging is associated with glucose intolerance, insulin resistance, and an increased risk of coronary artery disease, but that the effect of aging on coronary artery disease cannot be explained by insulin resistance alone. Other factors, such as glucose intolerance and increased blood pressure, in addition to insulin resistance, appear to be responsible of the increased risk for coronary artery disease in the elderly.