Shape of the OGTT glucose curve and risk of impaired glucose metabolism in the EGIR-RISC cohort

Objective To study whether the shape of the oral glucose tolerance test (OGTT)-glucose curve is a stable trait over time; it is associated with differences in insulin sensitivity, ß-cell function and risk of impaired fasting glucose (IFG) and glucose tolerance (IGT) in the Relationship between Insulin Sensitivity and Cardiovascular Disease (RISC) cohort. Methods OGTT-glucose curve shape was classified as monophasic, biphasic, triphasic and anomalous in 915 individuals. Oral glucose insulin sensitivity (OGIS), Matsuda insulin sensitivity index (ISI) and ß-cell function were assessed at baseline and 3 years apart. Results The OGTT-glucose curve had the same baseline shape after 3 years in 540 people (59%; κ = 0.115; p < 0.0001). Seventy percent of the participants presented with monophasic OGTT-glucose curve shape at baseline and after 3 years (percent positive agreement 0.74). Baseline monophasic shape was associated with significant increased risk of IFG (OR 1.514; 95% CI 1.084–2.116; p = 0.015); biphasic shape with reduced risk of IGT (OR 0.539; 95% CI 0.310–0.936) and triphasic shape with reduced risk of IFG (OR 0.493; 95% CI 0.228–1.066; P = 0.043) after 3 years. Increased risks of IFG (OR 1.509; 95% CI 1.008–2.260; p = 0.05) and IGT (OR 1.947; 95% CI 1.085–3.494; p = 0.02) were found in people who kept stable monophasic morphology over time and in switchers from biphasic to monophasic shape (OR of IGT = 3.085; 95% CI 1.377–6.912; p = 0.001). Conclusion After 3 years follow-up, the OGTT-glucose shape was stable in 59% of the RISC cohort. Shapes were associated with different OGIS and ß-cell function; persistence over time of the monophasic shape and switch from biphasic to monophasic shape with increased risk of impaired glucose metabolism.