Differences in early‐phase insulin secretion and glucose disposition index between aged and middle‐aged patients with newly diagnosed type 2 diabetes

AIM: This cross-sectional study aimed to investigate the differences in beta-cell function and insulin sensitivity between newly diagnosed aged and middle-aged type 2 diabetes mellitus (T2DM) patients. METHODS: A total of 206 newly diagnosed T2DM patients aged >/=60 years (A-DM group) and 206 newly diagnosed sex- and glycated hemoglobin-matched T2DM patients aged <60 years (MA-DM group) were recruited. All patients underwent the 75-g oral glucose tolerance test. Plasma glucose, lipid profiles, liver and renal function, glycated hemoglobin, and insulin were measured. Homeostasis model assessment for insulin resistance, quantitative insulin sensitivity check index, area under the curve of glucose during 0-30 min (GluAUC30) x area under the curve of insulin during 0-30 min (InsAUC30) and beta-cell function indexes were calculated. RESULTS: The mean age of the total 412 patients (356 men and 56 women) was 59.76 +/- 13.32 years. There were no significant differences in GluAUC120 between the two groups (106.89 +/- 27.70 in A-DM vs 108.32 +/- 27.58 in MA-DM; P = 0.6), but DeltaI30/DeltaG30, InsAUC30 and GluAUC30 x InsAUC30 levels were significantly higher in the A-DM group than in the MA-DM group (3.55 +/- 4.54 vs 2.53 +/- 3.83; P = 0.014, and 39.19 +/- 32.19 vs 32.71 +/- 28.81; P = 0.032, 675.05 +/- 475.60 vs 584.56 +/- 450.23; P = 0.048, respectively). The glucose disposition index (GDI) of the A-DM group was statistically higher than that of the MA-DM group (0.38 +/- 0.40 vs 0.30 +/- 0.35; P = 0.018). Age was positively associated with DeltaI30/DeltaG30 (r = 0.117; P = 0.017) and GDI (r = 0.147; P = 0.003), but had no correlation with InsAUC30, InsAUC120 or GluAUC30 x InsAUC30. After multiple adjustments for confounders, including sex, body mass index, glycated hemoglobin, triglyceride, total cholesterol and high-density lipoprotein cholesterol, age was positively associated with DeltaI30/DeltaG30, InsAUC30, InsAUC120, GluAUC30 x InsAUC30 and GDI. CONCLUSIONS: Aged patients have relatively higher early-phase insulin secretion and GDI than middle-aged patients in newly diagnosed T2DM. Geriatr Gerontol Int 2020; **: **-**.