Prediabetic increase in hemoglobin A1c compared with impaired fasting glucose in patients receiving antipsychotic drugs

Background: In 2010, the American Diabetes Association recommended that individuals with hemoglobin A1c 5.7-6.4% be classified as prediabetic even in the absence of impaired fasting glucose (IFG). Aim of study: To compare the clinical and metabolic characteristics of patients receiving antipsychotic drugs who have normal glucose tolerance (NGT), hemoglobin A1c 5.7-6.4% or IFG (fasting glucose 100-125 mg/dL). Method: Body mass index, waist circumference, fasting glucose, insulin, lipids, hemoglobin A1c, and insulin resistance assessed with the homeostatic model (HOMA-IR) were measured in a consecutive cohort of adult psychiatric inpatients with NGT (N=423), hemoglobin A1c 5.7-6.4% (N=130), IFG (N=52) and IFG plus hemoglobin A1c 5.7-6.4% (n=39). Results: The hemoglobin A1c 5.7-6.4% group had lower fasting insulin levels (9.8 +/- 5.6 vs. 15.5 +/- 11.4 mu U/mL, p<0.0001) and HOMA-IR (2.1 +/- 1.2 vs. 4.1 +/- 3.1, p<0.0001) than the IFG group, but were metabolically similar to those with NGT. The hemoglobin A1c 5.7-6.4% was the predominant prediabetic pattern in patients treated with antipsychotics other than clozapine or olanzapine. Patients with hemoglobin A1c 5.7-6.4% and those with IFG were statistically similar in age (40.1 +/- 13.6 vs. 39.7 +/- 10.3 years), body mass index (26.0 +/- 4.8 vs. 26.3 +/- 4.9) and waist circumference 93.1 +/- 13.9 vs. 98.1 +/- 12.1 cm for males and 92.5 +/- 13.5 vs. 90.7 +/- 15.8 cm for females. Conclusion: The hemoglobin A1c in the 5.7-6.4% range is common in euglycemic patients receiving antipsychotic drugs and this prediabetic pattern has metabolic and pharmacological features that differentiates it from IFG. (C) 2012 Elsevier B.V. and ECNP. All rights reserved.