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

Abstract

Elevated 2-h plasma glucose concentration (2h-PG) during a 75g OGTT predict the development of type 2 diabetes mellitus. However, 1-h plasma glucose concentration (1h-PG) is associated with insulin secretion and may be a better predictor of type 2 diabetes. We aimed to investigate the association between 1h-PG and 2h-PG using gold standard methods for measuring insulin secretion and action. We also compared 1h-PG and 2h-PG as predictors of type 2 diabetes mellitus. 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 1h-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 12.8years follow-up, respectively). Compared with 2h-PG (r=-0.281), 1h-PG (r=-0.384) was more closely associated with AIR, whereas, compared with 1h-PG (r=-0.340), 2h-PG (r=-0.408) was more closely associated with M. Measures of 1h-PG and 2h-PG had similar abilities to predict type 2 diabetes, which did not change when both were included in the model. A 1h-PG cut-off of 9.3mmol/l provided similar levels of sensitivity and specificity as a 2h-PG cut-off of 7.8mmol/l; the latter is used to define impaired glucose tolerance, a recognised predictor of type 2 diabetes mellitus. The 1h-PG was associated with important physiological predictors of type 2 diabetes and was as effective as 2h-PG for predicting type 2 diabetes mellitus. The 1h-PG is, therefore, an alternative method of identifying individuals with an elevated risk of type 2 diabetes mellitus.