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

Abstract

Background: 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.

Methods: 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.

Results: Within IGT, the adjusted HRs for T2DM significantly increased proportionally to 2-h PG level [<140mg/dL: reference, 140-159mg/dL: 3.07 (2.67-3.54), 160-179mg/dL: 5.44 (CI 4.66-6.34), 180-199mg/dL: 7.91 (CI 6.53-9.59)]. IGT combined with IFG had the profoundly increased HRs than isolated IFG. Even within normal glucose tolerance (NGT), 2-h PG level≥120mg/dL had the higher risk for T2DM than other NGT groups. These associations were more dominant in male than female.

Conclusion: The highest level of 2h-PG (180-199mg/dL) in IGT and IGT with IFG were strong predictor for T2DM. 2-h PG of 120-139mg/dL was more significantly associated with T2DM within NGT, and male was more susceptible for T2DM than female.

Keywords: Diabetes mellitus; Impaired fasting glucose; Impaired glucose tolerance; Oral glucose tolerance test.