Antipsychotic exposure and type 2 diabetes among patients with schizophrenia: a matched case‐control study of California Medicaid claims

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Abstract
Purpose To examine the risk of developing type 2 diabetes mellitus among people with schizophrenia exposed to atypical antipsychotics (clozapine, olanzapine, quetiapine, risperidone) compared to those exposed to conventional antipsychotics. Methods A matched case‐control design was used to examine California Medicaid beneficiaries. Cases developed diabetes subsequent to being diagnosed with schizophrenia (ICD‐9295), were 18 years or older, and were exposed to at least one antipsychotic medication at some point during the 12 weeks preceding diabetes diagnosis. Diabetes was defined by diagnostic claim (ICD‐9250) or prescription for antidiabetic agents. A total of 3663 cases were matched to 14 523 non‐diabetic controls (people with schizophrenia matched on gender and age ±5 years). All had to be continuously eligible for benefits during the 12‐week period preceding diabetes onset in the case. Conditional logistic regression modeled the risk of exposure, controlling for age, ethnicity, and exposure to selected concomitant medications. Analyses were repeated with 24‐ and 52‐week exposure windows. Results Using a 12‐week exposure window, olanzapine (OR = 1.36, 95%CI 1.20–1.53), clozapine (OR = 1.34, 95%CI 1.16–1.55), and combination atypical therapy (OR = 1.58, 95%CI 1.33–1.88), but not risperidone or quetiapine, were associated with increased odds of developing diabetes compared to conventional antipsychotics. Changing to a 24‐week exposure window, the risks were: olanzapine (OR = 1.38, 95%CI 1.22–1.56), clozapine (OR = 1.32, 95%CI 1.14–1.53), or combinations (OR = 1.54, 95%CI 1.29–1.84). With a 52‐week exposure window, the risks were: olanzapine (OR = 1.41, 95%CI 1.24–1.60), clozapine (OR = 1.41, 95%CI 1.21–1.65), combinations (OR = 1.58, 95%CI 1.31–1.90). Risk for olanzapine increased with dose. Hispanic, African American, and unknown ethnicity were significant risks for development of type 2 diabetes as was exposure to selected concomitant medications. Conclusions Exposure to olanzapine or clozapine is associated with a 34–41% increase in the developing of type 2 diabetes among California Medicaid recipients with schizophrenia. Prospective, randomized trials are needed to confirm these retrospective, observational findings. Copyright © 2005 John Wiley & Sons, Ltd.