Rate of new-onset diabetes among patients treated with atypical or conventional antipsychotic medications for schizophrenia.

CONTEXT Understanding the association between use of antipsychotics and onset of diabetes. OBJECTIVE To compare the rates of new-onset diabetes mellitus (DM) between patients treated for schizophrenia with atypical or conventional antipsychotics. DESIGN Retrospective analysis of medical and pharmacy claims data. SETTING 61 US health plans. PATIENTS Patients with schizophrenia who were treated with atypical or conventional antipsychotics between September 1996 and June 2001 and were enrolled for 12 or more months before and 3 or more months after therapy initiation. MAIN OUTCOME MEASURES New-onset DM was defined based on 2 or more claims with a diabetes diagnosis or initiation of antidiabetic therapy during follow-up. Rates of DM were compared between patients receiving atypical and conventional antipsychotics, and among 4 subgroups of patients receiving atypical antipsychotics (olanzapine, clozapine, risperidone, quetiapine). Statistical analyses employed logistic regression and Cox proportional hazards models. RESULTS Patients treated with atypical antipsychotics (N = 1826) were younger, had a lower rate of diagnosed hypertension, and longer duration of therapy than those receiving conventional antipsychotics (N = 617). The crude incidence of DM did not differ (2.46% vs 2.76% for atypical antipsychotics and conventional antipsychotics, P =.525). In Cox proportional hazards models, patients treated with atypical antipsychotics had a statistically significant, moderately increased risk of DM relative to conventional antipsychotics (hazard ratio [HR] = 1.17, 95% confidence interval [CI] = 1.06, 1.30); no significant differences in risk were observed when atypical antipsychotic cohorts were compared. In logistic regression models, no significant differences in DM risk were observed. CONCLUSIONS Patients with schizophrenia treated with atypical antipsychotics had a moderately increased risk of DM relative to those treated with conventional antipsychotics, as measured by Cox proportional hazards models; such risk was not significantly different among patients treated with individual atypical medications.