Relationship Between β-Cell Function and Glycated Hemoglobin: Results from the Veterans Administration Genetic Epidemiology Study

OBJECTIVE: The study objective was to assess the relationship between β-cell function and HbA₁c. RESEARCH DESIGN AND METHODS: A total of 522 Mexican American subjects participated in this study. Each subject received a 75-g oral glucose tolerance test (OGTT) after a 10- to 12-h overnight fast. Insulin sensitivity was assessed with the Matsuda index. Insulin secretory rate was quantitated from deconvolution of the plasma C-peptide concentration. β-Cell function was assessed with the insulin secretion/insulin resistance (IS/IR) (disposition) index and was related to the level of HbA₁c. RESULTS: At HbA₁c levels 5.5%, there was a precipitous decrease in both the Matsuda index and the IS/IR index. Subjects with HbA₁c = 6.0-6.4% had a 44 and 74% decrease in the Matsuda index and the IS/IR index, respectively, compared with subjects with HbA₁c