LAUSR

BACKGROUND To explore the correlations between glycosylated hemoglobin (HbA1c) and glucose levels in older adults with newly diagnosed type 2 diabetes mellitus (T2DM). METHODS A total of 783 participants aged ≥60 years were enrolled. The 75-g oral glucose tolerance test (OGTT) was conducted and HbA1c was measured. The participants were divided into normal glucose tolerance (NGT)HbA1c, Pre-DMHbA1c, and T2DMHbA1c groups based on the HbA1c diagnostic criteria. The correlations between HbA1c and glucose levels of the OGTT were analyzed. RESULTS When HbA1c ≥ 6.5% in older people, HbA1c was positively correlated with Glucose 0 min and 120 min of the OGTT (r = 0.335, 0.247; all p < 0.05, respectively). When HbA1c was between 5.7% and 6.4%, HbA1c was positively correlated with Glucose 0 min and 120 min (r = 0.298, 0.474; all p < 0.01, respectively). When HbA1c ≤ 5.6%, HbA1c was positively correlated with Glucose 0 min and 120 min (r = 0.301, 0.357; all p < 0.01, respectively). HbA1c was positively correlated with HOMA-IR (r = 0.368, p < 0.01), while it was negatively correlated with HOMA-β, ΔI30/ΔG30, IG120, and GDI(r = -0.267, -0.397,-0.364,-0.397; all p < 0.01, respectively). After adjustment for confounders, the correlations of HbA1c with Glucose 0 min and 120 min, insulin sensitivity and β-cell function indexes still existed. When HbA1c ≥ 6.5%, there were 93.3% T2DMOGTT and 6.7% Pre-DMOGTT subjects. When HbA1c < 6.5%, there were 17.7% T2DMOGTT, 39.5% Pre-DMOGTT (including 2.5% IFGOGTT, 36.1% IGTOGTT and 0.9% IGROGTT), and 42.8% NGTOGTT subjects. DISCUSSION When HbA1c ≥ 6.5% in older people, HbA1c shows the highest correlation with Glucose 0 min of the OGTT. When HbA1c < 6.5%, postprandial hyperglycemia is a main characteristic of older people, and HbA1c shows the highest correlation with Glucose 120 min of the OGTT.