In 2010, the American Diabetes Association (ADA) proposed that individuals with fasting glucose 100–125 mg/dl (5.6-6.9 mmol/l) or glucose 140–199 mg/dl (7.8–11.0 mmol/l) 2 hours after a 75 gm oral glucose tolerance test (OGGT) or hemoglobin A1c (A1c) 5.7–6.4% be classified as prediabetic to indicate a high risk for the development of diabetes.

To determine the prevalence of prediabetes in psychiatric patients receiving antipsychotics and to compare the clinical and metabolic features of patients with normal glucose tolerance, prediabetes and diabetes.

The 2010 ADA criteria were applied to a large consecutive cohort of psychiatric patients treated at one institution in Belgium. All patients were evaluated with OGTT, A1c, insulin levels and lipid profiles.

The study sample was restricted to the 783 adult patients (mean age 37.6) without known history of diabetes. 413 (52.8%) patients had normal glucose tolerance, 290 (37%) were prediabetic and 80 (10.2%) were diabetic. The 3 groups were similar with regard to psychiatric diagnoses, severity of mental illness and antipsychotic treatment. A statistically significant crescendo gradient from normal to prediabetes and from prediabetes to diabetes was observed for age, body mass index, waist circumference, fasting insulin, homeostatic model of insulin resistance (HOMA-IR) and triglyceride levels. The intergroups differences for fasting insulin and HOMA-IR were confirmed for treatment with clozapine, olanzapine, quetiapine, risperidone and amilsulpride, but not for aripiprazole or first-generation antipsychotics.

Prediabetes is highly prevalent in adults treated with antipsychotic drugs and correlates with markers of intraabdominal adiposity and insulin resistance.