ORIGINAL ARTICLE Impact of Medication Adherence on Hospitalization Risk and Healthcare Cost

Objective: The objective of this study was to evaluate the impact of medication adherence on healthcare utilization and cost for 4 chronic conditions that are major drivers of drug spending: diabetes, hypertension, hypercholesterolemia, and congestive heart failure. Research Design: The authors conducted a retrospective cohort observation of patients who were continuously enrolled in medical and prescription benefit plans from June 1997 through May 1999. Patients were identified for disease-specific analysis based on claims for outpatient, emergency room, or inpatient services during the first 12 months of the study. Using an integrated analysis of administra-tive claims data, medical and drug utilization were measured during the 12-month period after patient identification. Medication adher-ence was defined by days ’ supply of maintenance medications for each condition. Patients: The study consisted of a population-based sample of 137,277 patients under age 65. Measures: Disease-related and all-cause medical costs, drug costs, and hospitalization risk were measured. Using regression analysis, these measures were modeled at varying levels of medication ad-herence. Results: For diabetes and hypercholesterolemia, a high level of medication adherence was associated with lower disease-related medical costs. For these conditions, higher medication costs were more than offset by medical cost reductions, producing a net reduction in overall healthcare costs. For diabetes, hypercholester-olemia, and hypertension, cost offsets were observed for all-cause medical costs at high levels of medication adherence. For all 4 conditions, hospitalization rates were significantly lower for patients with high medication adherence. Conclusions: For some chronic conditions, increased drug utiliza-tion can provide a net economic return when it is driven by improved adherence with guidelines-based therapy. Key Words: adherence, drug utilization, healthcare costs, hospitalization, pharmaceutical car