Evaluation of simple indices of insulin sensitivity and insulin secretion for use in epidemiologic studies

The metabolic characteristics of type 2 diabetes, insulin resistance, and d iminished insulin secretion are costly to measure directly. To evaluate the utility of several simple indices derived from insulin and glucose measure ments, the indices were examined from 1982 to 1997 with respect to correlat ion with more sophisticated measures or insulin sensitivity and secretion i n Pima Indians in the Gila River Indian Community of Arizona. Ability to pr edict the incidence of diabetes in 1,731 persons was also examined. Indices were calculated from fasting and 2-hour glucose (G(0), G(120)) and insulin (I-0, I-120) concentrations obtained during an oral glucose tolerance test . Pasting serum insulin concentration and the insulin sensitivity index (10 (4)/(I-0 x G(0))) each showed a moderate correlation with the estimate of i nsulin sensitivity derived from the hyperinsulinemiceuglycemic cramp (\r\ a pproximate to 0.60) They also strongly predicted the incidence of diabetes (incidence rate ratio comparing the most and least insulin-resistant tertil e groups approximate to 3.0), Corrected insulin response (I-120/(G(120) x ( G(120) - 70))) was modestly correlated with insulin secretion as measured b y an intravenous glucose tolerance test (r = 0.35), Impaired insulin secret ion assessed by this index predicted incidence of diabetes, particularly af ter control for insulin sensitivity index (incidence rate ratio = 1.6). Thu s, simple indices of insulin sensitivity and secretion may be reasonable su rrogates for more sophisticated measures in epidemiologic studies.