Assessment of independent effect of olanzapine and risperidone on risk of diabetes among patients with schizophrenia: population based nested case-control study

OBJECTIVE: To quantify the association between olanzapine and diabetes. DESIGN: Population based nested case-control study. SETTING: United Kingdom based General Practice Research Database comprising 3.5 million patients followed between 1987 and 2000. PARTICIPANTS: 19 637 patients who had been diagnosed as having and treated for schizophrenia. 451 incident cases of diabetes were matched with 2696 controls. MAIN OUTCOME MEASURES: Diagnosis and treatment of diabetes. RESULTS: Patients taking olanzapine had a significantly increased risk of developing diabetes than non-users of antipsychotics (odds ratio 5.8, 95% confidence interval 2.0 to 16.7) and those taking conventional antipsychotics (4.2, 1.5 to 12.2). Patients taking risperidone had a non-significant increased risk of developing diabetes than non-users of antipsychotics (2.2, 0.9 to 5.2) and those taking conventional antipsychotics (1.6, 0.7 to 3.8). CONCLUSION: Olanzapine is associated with a clinically important and significant increased risk of diabetes.