Limited Overlap Between Intermediate Hyperglycemia as Defined by A1C 5.7–6.4%, Impaired Fasting Glucose, and Impaired Glucose Tolerance

OBJECTIVE: We compared the prevalences and overlap between intermediate hyperglycemia (IH), defined by a hemoglobin A(1c) (A1C) 5.7–6.4%, impaired fasting glucose (IFG), and impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS: Oral glucose tolerance test results and A1C measurements were evaluated as markers of IH in an unselected cohort of 486 nondiabetic adults from Finland. RESULTS: The overall prevalence of IH was 34%. Prevalences of isolated A1C 5.7–6.4%, IGT, and IFG were 8.0, 13.2, and 4.5%, respectively. Overlap between these three markers was uncommon. Isolated A1C 5.7–6.4% was associated with a higher BMI compared with isolated IFG and IGT and with a more adverse lipid profile compared with isolated IFG. CONCLUSIONS: Prevalence of isolated IH was high, with limited overlap between the definitions. Differences in cardiovascular disease risk factors were observed among the groups. This study demonstrates that an A1C of 5.7–6.4% detects, in part, different individuals with IH compared with IFG and IGT.