Incident diabetes associated with second-generation antipsychotic therapy : an evaluation of the impact of dose and treatment indication



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The impact of antipsychotic dose and treatment indication on the risk of newonset diabetes associated with use of second-generation antipsychotic (SGA) monotherapy were assessed using medical data from Texas Medicaid. Eligible enrollees aged ≥18 years of age were followed for a maximum of 12 months between 1997 and 2001. Patients were stratified according to treatment dose (low, medium, high) and a hierarchy of mutually exclusive diagnostic categories: schizophrenia; bipolar disorder; dementia; psychotic disorder; non-psychotic disorder; and no mental health indication. The average patient age (N=19,430) was 60.3 years (SD: 21.9); the majority of whom were White (55.1%) females (65.7%) aged ≥60 years (50.4%). At treatment-onset, the prevalence of diabetes was 16.9%. The mean (SD) dose for the most prevalent conditions (schizophrenia, bipolar disorder and dementia, respectively) were as follows: olanzapine (12.04mg (6.73); 8.91mg (5.78); 4.87mg (3.00)); quetiapine (273.16mg (203.86)); 146.33mg (142.29); 79.59 (82.57)); and risperidone (3.55mg (2.37); 2.05 (1.76); 1.12 (0.85)). The incidence of diabetes was 2.37%. After controlling for demographic, clinical and medication variables, no difference (p=0.281) was noted in the incidence of diabetes according to the specific SGA used (N=7,842). Compared to risperidone, the odds of new-onset diabetes were 0.879 (95% CI: 0.653 to 1.184) and 0.683 (95% CI: 0.414 to 1.126) for olanzapine and quetiapine, respectively. Neither treatment indication (p=0.876) nor dose (p=0.274) were associated with the development of diabetes. When examined according to the individual SGA, the incidence of diabetes did not differ (p≥0.292) according to antipsychotic dose or treatment indication for quetiapine and risperidone. For olanzapine, while no difference was noted according to the dose used (p=0.384), the incidence of diabetes differed according to the treatment indication (p=0.034), with a significant increase in the odds of diabetes noted for those with a psychotic disorder (OR: 2.911, 95%CI: 1.088 to 7.790) or a nonpsychotic disorder (OR: 2.433, 95%CI: 1.042 to 5.680) compared to schizophrenia. Results indicate that the risk of new-onset diabetes does not differ among the SGA agents. While the dose of antipsychotic prescribed varied significantly according to treatment indication and patient age, neither dose nor treatment indication were associated with the development of diabetes.