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

J. Steven Lamberti, M.D.; G. Oana Costea, M.D.; David Olson, Ph.D., R.Ph.; John F. Crilly, M.D.; Kumar Maharaj, R.Ph., M.S.B.A.; Xin Tu, Ph.D.; Adrienne Groman, M.S.; Marci B. Dietz, M.S., R.N., C.S.; Margaret P. Bushey, M.S., N.P.; Telva Olivares, M.D.; and Karen Wiener, M.D.

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.

(J Clin Psychiatry 2005;66:900-906)

Received Sept. 10, 2004; accepted Jan. 1, 2005. From the Department of Psychiatry, University of Rochester Medical Center, Rochester, N.Y.

This work was supported by a grant from the Committee to Aid Research to End Schizophrenia, Pittsford, N.Y.

Presented at the 156th annual meeting of the American Psychiatric Association, San Francisco, Calif., May 17-22, 2003.

Dr. Lamberti has been a consultant for and has served on the speakers or advisory boards of Eli Lilly, Janssen, Pfizer, AstraZeneca, and Novartis; and has received grant/research support from Eli Lilly, Janssen, and Bristol-Myers Squibb. Dr. Weiner has served on the speakers or advisory boards of AstraZeneca and Eli Lilly. No other author reported any disclosures.

Corresponding author and reprints: J. Steven Lamberti, M.D., Department of Psychiatry, University of Rochester Medical Center, 300 Crittenden Blvd., Rochester, NY 14642 (e-mail: steve_lamberti@urmc.rochester.edu).