The risk of type 2 diabetes mellitus according to 2-h plasma glucose level: The Korean Genome and Epidemiology Study (KoGES)

•Individuals with IGT have the different risk of type 2 diabetes (T2DM).•IGT combined with IFG and high 2-h plasma glucose were strong predictor of T2DM.•The risk for T2DM increased proportionally even in normal glucose tolerance. Although impaired glucose tolerance (IGT) is a definite risk factor for type 2 diabetes mellitus (T2DM), there is limited information about the risk stratification for incident T2DM within IGT group. Thus, we aimed to evaluate the incidental risk for T2DM according to 2-h plasma glucose (2-h PG) level of oral glucose tolerance test (OGTT) and phenotype of IGT. 7654 Korean participated in the Korean Genome and Epidemiology Study (KoGES) were stratified by 2-h PG levels of OGTT, and followed up for 63,665 person-years. Cox proportional hazards model was used to calculate the hazard ratios (HRs) and 95% confidential interval (CI) for T2DM according to 2-h PG levels of OGTT with adjustment for multiple covariates. Subgroup analysis was performed by gender and the presence of impaired fasting glucose (IFG) or not. Within IGT, the adjusted HRs for T2DM significantly increased proportionally to 2-h PG level [