One-hour and two-hour postload plasma glucose concentrations are comparable predictors of type 2 diabetes mellitus in Southwestern Native Americans

Abstract

Aims/hypothesis: Elevated 2-h plasma glucose concentration (2 h-PG) during a 75 g OGTT predict the development of type 2 diabetes mellitus. However, 1-h plasma glucose concentration (1 h-PG) is associated with insulin secretion and may be a better predictor of type 2 diabetes. We aimed to investigate the association between 1 h-PG and 2 h-PG using gold standard methods for measuring insulin secretion and action. We also compared 1 h-PG and 2 h-PG as predictors of type 2 diabetes mellitus.

Methods: This analysis included adult volunteers without diabetes, predominantly Native Americans of Southwestern heritage, who were involved in a longitudinal epidemiological study from 1965 to 2007, with a baseline OGTT that included measurement of 1 h-PG. Group 1 (n = 716) underwent an IVGTT and hyperinsulinaemic-euglycaemic clamp for measurement of acute insulin response (AIR) and insulin-stimulated glucose disposal (M), respectively. Some members of Group 1 (n = 490 of 716) and members of a second, larger, group (Group 2; n = 1946) were followed-up to assess the development of type 2 diabetes (median 9.0 and 12.8 years follow-up, respectively).

Results: Compared with 2 h-PG (r = -0.281), 1 h-PG (r = -0.384) was more closely associated with AIR, whereas, compared with 1 h-PG (r = -0.340), 2 h-PG (r = -0.408) was more closely associated with M. Measures of 1 h-PG and 2 h-PG had similar abilities to predict type 2 diabetes, which did not change when both were included in the model. A 1 h-PG cut-off of 9.3 mmol/l provided similar levels of sensitivity and specificity as a 2 h-PG cut-off of 7.8 mmol/l; the latter is used to define impaired glucose tolerance, a recognised predictor of type 2 diabetes mellitus.

Conclusions/interpretation: The 1 h-PG was associated with important physiological predictors of type 2 diabetes and was as effective as 2 h-PG for predicting type 2 diabetes mellitus. The 1 h-PG is, therefore, an alternative method of identifying individuals with an elevated risk of type 2 diabetes mellitus.

Keywords: 1-h plasma glucose; 2-h plasma glucose; Acute insulin response; Hyperinsulinaemic–euglycaemic clamp; OGTT; Prediction; Type 2 diabetes mellitus.

Fig. 1

ROC curves based on the predicted cumulative incidence of type 2 diabetes by the Kaplan–Meier method for 1 h-PG (solid lines) and 2 h-PG (dashed lines) at (a) 5 years (AUC: 0.672 for 1 h-PG, 0.658 for 2 h-PG) and (b) 25 years (AUC: 0.728 for 1 h-PG, 0.706 for 2 h-PG). Blue diamond (9.3 mmol/l) indicates the 1 h-PG cut-off closest to the 2 h-PG cut-off of 7.8 mmol/l (open grey triangle). Black triangle indicates the previously reported 1 h-PG cut-off (8.6 mmol/l) [5]