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 μU/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.