Diabetes Mellitus Among Outpatients Receiving Clozapine: Prevalence and Clinical-Demographic Correlates

Background: Treatment with antipsychotic drugs has been associated with increased risk for developing diabetes mellitus. Recent consensus statements suggest that clozapine may pose an especially high risk. The purpose of this study is to examine the prevalence and clinical-demographic correlates of diabetes among outpatients with DSM-IV-diagnosed schizophrenia or schizoaffective disorder receiving clozapine.

Method: One hundred one outpatients receiving clozapine at the University of Rochester Department of Psychiatry, Rochester, N.Y., were evaluated between September 2002 and September 2003. Demographic data were collected from medical records, and body mass index (BMI) and body fat measurements were conducted. Diagnosis of diabetes was established through review of medical records and fasting blood glucose testing. Associations between clinical and demographic variables and diabetes were examined using t tests, Fisher exact tests, and logistic regression.

Results: Mean (SD) age of patients was 40.4 (9.5) years, and 79% were white. Mean (SD) dose and duration of clozapine treatment were 426 (164) mg/day and 5.7 (3.6) years, respectively. Point prevalence of diabetes was 25.7%. Mean (SD) BMI was 32.6 (8.0) kg/m², and mean (SD) body fat was 34.0% (11.0%). Logistic regression revealed significant associations between diabetes and nonwhite race/ethnicity and family history of diabetes (p = .02 and .002, respectively). No significant associations were found between diabetes prevalence and BMI or body fat.

Conclusion: Patients receiving clozapine are at substantial risk for developing diabetes, although the level of risk relative to other antipsychotic medications has not been fully determined. Clinicians should monitor all severely mentally ill patients receiving antipsychotic drugs for diabetes, with closer monitoring of patients with established demographic risk factors.