To assess the prevalence of prediabetes and metabolic abnormalities among overweight or obese clozapine- or olanzapine-treated schizophrenia patients, and to identify characteristics of the schizophrenia group with prediabetes.

A cross-sectional study assessing the presence of prediabetes and metabolic abnormalities in schizophrenia clozapine- or olanzapine-treated patients with a body mass index (BMI) ≥27 kg/m2. Procedures were part of the screening process for a randomized, placebo-controlled trial evaluating liraglutide vs placebo for improving glucose tolerance. For comparison, an age-, sex-, and BMI-matched healthy control group without psychiatric illness and prediabetes was included. Prediabetes was defined as elevated fasting plasma glucose and/or impaired glucose tolerance and/or elevated glycated hemoglobin A1c.

Among 145 schizophrenia patients (age = 42.1 years; males = 59.3%) on clozapine or olanzapine (clozapine/olanzapine/both: 73.8%/24.1%/2.1%), prediabetes was present in 69.7% (101 out of 145). While schizophrenia patients with and without prediabetes did not differ regarding demographic, illness, or antipsychotic treatment variables, metabolic abnormalities (waist circumference: 116.7±13.7 vs 110.1±13.6 cm, P = 0.007; triglycerides: 2.3±1.4 vs 1.6±0.9 mmol/L, P = 0.0004) and metabolic syndrome (76.2% vs 40.9%, P<0.0001) were significantly more pronounced in schizophrenia patients with vs without prediabetes. The age-, sex-, and BMI-matched healthy controls had significantly better glucose tolerance compared to both groups of patients with schizophrenia. The healthy controls also had higher levels of high-density lipoprotein compared to patients with schizophrenia and prediabetes.

Prediabetes and metabolic abnormalities were highly prevalent among the clozapine- and olanzapine-treated patients with schizophrenia, putting these patients at great risk for later type 2 diabetes and cardiovascular disease. These results stress the importance of identifying and adequately treating prediabetes and metabolic abnormalities among clozapine- and olanzapine-treated patients with schizophrenia.