Glucose dysregulation among veterans living with schizophrenia-related disorders after switching second-generation antipsychotics

Objectives: To compare (1) blood glucose and glycosylated hemoglobin (A1C) laboratory results and (2) longitudinal trends in blood glucose levels among veterans switched from one second-generation antipsychotic (SGA) to another. Design: Retrospective, naturalistic, nonequivalent control group. Setting: United States between April 1, 2003, and September 30, 2003. Patients: 1,776 U. S. Veterans Health System beneficiaries living with schizophrenia-related disorders switching (1) from olanzapine to another SGA, (2) to olanzapine from another SGA, and (3) among nonolanzapine SGAs. Intervention: Data were retrieved from the laboratory results (LAR) database for a maximum of 180 days before and 365 days after the index date. Main outcome measures: Mean blood glucose, A1C, and change in blood glucose. Results: Blood glucose (36.0 mg/dL, paired t test((109)) = -4.87, P < 0.001) and A1C (1.0%, paired t((143)) = -4.84, P < 0.001) declined among veterans switched from olanzapine who were taking a blood glucose-lowering agent before the switch but was unchanged for those who were not. Adjusting for age, gender, and race, addition of the switch-type variables improved prediction of blood glucose change (F-ratio = 3.76, P = 0.03). Linear mixed-effects models confirmed that blood glucose levels declined for veterans switched from olanzapine with glucose dysregulation before the switch (Est(beta(2)-beta(1)) = -34.5 mg/dL, t((424)) = -5.05, P < 0.001). Conclusion: Blood glucose and A1C were significantly improved among veterans switched from olanzapine with evidence of glucose dysregulation before the switch. They were stable among those without evidence of preexisting glucose dysregulation. Therapeutic switches from one SGA to another should be monitored as a risk factor for changes in glucose regulation.