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.