Insulin sensitivity and secretion indices in Japanese subjects with normal and impaired glucose tolerance

The aim of this study was to identify clinical factors that were associated with insulin sensitivity and secretion by multiple linear regression analysis in Japanese subjects with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT). A total of 2,983 subjects were classified into two groups, NGT and IGT, according to the oral glucose tolerance test criteria. To assess insulin sensitivity, homeostasis model assessment (HOMA)-S and the Matsuda index were used. To determine insulin secretion, HOMA-β, the insulinogenic index (IGI), basal disposition index (DI), and early phase DI were calculated. Stepwise multiple regression analyses were performed to examine the relationships between these indices and certain clinical factors, such as body mass index (BMI), HbA1c, age, sex, and family history. BMI was the only significant factor associated with HOMA-S. For the Matsuda index, the most important factor was BMI, followed by age and sex. BMI, HbA1c, age, sex, and family history were significantly associated with HOMA-β, IGI, basal DI, and early phase DI. The standardized partial regression coefficients of HOMA-β and IGI were highest for BMI. For basal DI and early phase DI, the highest standardized partial regression coefficient was found to be HbA1c, followed by age and BMI. Basal DI and early phase DI were more useful than HOMA-β and IGI to assess insulin secretion. The most important factors associated with insulin sensitivity and secretion are BMI and HbA1c, respectively. Age is more associated with insulin secretion than with insulin sensitivity.