Risk of rehospitalization among bipolar disorder patients who are nonadherent to antipsychotic therapy after hospital discharge.

PURPOSE: The relationship between nonadherence to antipsychotic medication after hospital discharge and risk of rehospitalization in patients who were previously hospitalized for treatment of bipolar disorder was studied.
METHODS: Administrative claims data from 2000 through 2006 were obtained from commercial insurance plans. Patients age 18-64 years who were discharged from a hospital with a diagnosis of bipolar disorder and given a prescription for an antipsychotic 0-14 days after discharge comprised the study sample. Adherence to antipsychotic medication was determined by measuring the number of unique days during which medication was supplied during the treatment period, a calculation known as the medication possession ratio (MPR). Rehospitalization was considered to be an indicator of relapse. A multivariate, stepwise logistic regression, which controlled for patient characteristics, type of bipolar disorder, general health status, and comorbid conditions, was used to assess the relationship between medication non-adherence and rehospitalization.
RESULTS: A total of 1973 individuals were included in the analyses. The mean +/- S.D. MPR for this patient population was 0.46 +/- 0.32. Patients whose MPR was 0.75 or greater had a lower risk of all-cause rehospitalization (odds ratio [OR], 0.730; 95% confidence interval [CI], 0.580-0.919) and a lower risk of a mental-health-related rehospitalization (OR, 0.759; 95% CI, 0.603-0.955). As medication adherence increased above the MPR of 0.75, the risk of rehospitalization significantly decreased.
CONCLUSION: Among patients who were previously hospitalized for treatment of bipolar disorder, those who were adherent to their antipsychotic medication at least 75% of the time had lower risks of all-cause rehospitalization and mental-health-related rehospitalization.