Impact of Medication Adherence on Health Services Utilization in Medicaid.

Objective: To examine the impact of adherence to chronic disease medications on health services utilization among Medicaid enrollees.

Subjects: Eligibility, claims, and encounter data from the Medicaid Analytic Extract files from 10 states (Alabama, California, Florida, Illinois, Indiana, Louisiana, New Hampshire, New Mexico, New York, and Virginia) were used to construct a 3-year (2008-2010), longitudinal dataset of Medicaid recipients 18-64 years of age, including 656,646 blind/disabled individuals and 704,368 other adults. Patients were classified as having ≥1 of 7 chronic conditions: (1) congestive heart failure; (2) hypertension; (3) dyslipidemia; (4) diabetes; (5) asthma/chronic obstructive pulmonary disease; (6) depression; and (7) schizophrenia/bipolar.

Methods: Poisson regression was used to estimate associations between medication adherence [continuous and categorical proportion of days covered (PDC)] and 3 dependent variables: number of inpatient hospitalizations, emergency department visits, and outpatient physician/clinic visits.

Results: Full adherence was associated with 8%-26% fewer hospitalizations and 3%-12% fewer emergency department visits among those with congestive heart failure, hypertension, diabetes, and schizophrenia/bipolar. In all analyses, full adherence was associated with up to 15% fewer outpatient physician/clinic visits. Moreover, low and moderate levels of adherence were also related to less health care use.

Conclusions: Substantial reductions in health services utilization and costs may be realized with improved medication adherence in Medicaid. These benefits begin to accrue at adherence levels below the common 0.80 PDC threshold. Therefore, interventions should focus not just on perfecting moderate adherers, but also on encouraging Medicaid patients with chronic conditions to initiate pharmacotherapy.