Using drug claims data to assess the relationship of medication adherence with hospitalization and costs

Objective: This naturalistic study used claims data to examine the relation ship of medication nonadherence to hospital use and costs among severely me ntally ill clients in Wisconsin. Methods: Data for 619 clients were obtaine d from Medicaid drug and hospital claims, county records, and case managers as part of a larger study in eight county-based mental health systems. Stu dy participants were eligible for Medicaid, had a severe and persistent men tal illness, were 18 years or older, and were receiving neuroleptics, lithi um, or antidepressants. Drug claims were analyzed for a 12-month period to determine how regularly clients obtained their medications. Regression anal yses were used to assess the effects of irregular medication use on any hos pitalization for psychiatric problems, the number of days hospitalized, and hospital costs. The analyses controlled for several risk factors. Results: Among clients with schizophrenia or schizoaffective disorder, 31 percent u sed medications irregularly. The rates were 33 percent among those with bip olar disorder and 41 percent among those with other severe mental illnesses . In the total sample, irregular users had significantly higher rates of ho spitalization than regular users (42 percent versus 20 percent), more hospi tal days (16 days versus four days), and higher hospital costs ($3,992 vers us $1,048). Irregular medication use was one of the strongest predictors Of hospital use and costs even after the analyses controlled for diagnosis, d emographic characteristics, baseline functioning, and previous hospitalizat ions. Conclusions: The availability of drug claims data and the ability to use them in predictive analyses make them a potentially useful data source in studies of medication adherence among persons with severe mental illness .