Determinants of Glycated Hemoglobin in Subjects With Impaired Glucose Tolerance: Subanalysis of the Japan Diabetes Prevention Program

BACKGROUND Limited evidence is available about the relationship of lifestyle factors with glycated hemoglobin (HbA1c) in subjects with impaired glucose tolerance. The aim of study was to identify such determinant factors of HbA1c in subjects with impaired glucose tolerance. METHODS This cross-sectional study included 121 men and 124 women with impaired glucose tolerance, who were diagnosed based on a 75-g oral glucose tolerance test. Demographic and biochemical parameters, including the body mass index (BMI), fasting plasma glucose (FPG), 2-h post-load glucose (2-h PG), and HbA1c, were measured. The pancreatic β-cell function and insulin resistance were assessed using homeostasis model assessment (HOMA-β). Dietary intake was assessed by a food frequency questionnaire. RESULTS The levels of FPG, 2-h PG, and carbohydrate intake were correlated with the HbA1c level in men, while the FPG and 2-h PG levels were correlated with the HbA1c level in women. In multiple regression analyses, BMI, FPG, 2-h PG, and white rice intake were associated with HbA1c levels in men, while BMI, FPG, HOMA-β, and bread intake were associated with HbA1c levels in women. CONCLUSIONS The present findings suggest that a substantial portion of HbA1c may be composed of not only glycemic but also several lifestyle factors in men with impaired glucose tolerance. These factors can be taken into consideration as modifiable determinants in assessing the HbA1c level for the diagnosis and therapeutic monitoring of the disease course.