Prevalence of diabetes and antipsychotic prescription patterns in patients with schizophrenia: A nationwide retrospective cohort study

IntroductionDespite an increasing concern that atypical antipsychotics seem to have a stronger diabetogenic risk than conventional antipsychotics, little information is available on the prevalence of diabetes among schizophrenia patients, and prescription patterns for patients with comorbid schizophrenia and diabetes in Japan.ObjectivesTo compare the prevalence of diabetes between schizophrenia patients and the general population and to investigate whether diabetes status correlates the prescription patterns of antipsychotics at hospital discharge.MethodsSchizophrenia patients who were discharged between April 2004 and March 2005 and who continued to receive outpatient treatment from 526 hospitals were included in this retrospective open cohort study. We collected information about the doctor diagnosis of diabetes during hospitalization, and drug prescriptions for schizophrenia at hospital discharge using medical charts.ResultsThe overall prevalence of diabetes was 8.6% among patients with schizophrenia. Compared with the general population, the estimates of diabetes prevalence in the schizophrenia population were 2.6–10.8 percentage point higher among males aged 30–49 years, and 1.9–9.9 percentage point higher among females aged 40–59 years. The odds of being prescribed conventional antipsychotics were about 2 times higher among patients with diabetes than without diabetes, relative to atypical and combination of conventional and atypical antipsychotics. These results were robust across various sensitivity analyses.ConclusionWhen treating schizophrenia patients with preexisting diabetes, psychiatrists need to monitor the occurrence of diabetes regularly regardless of antipsychotic class, strike a balance, and provide the most efficacious antipsychotic medication.