Association Between Medication Adherence and Healthcare Costs Among Patients Receiving the Low-Income Subsidy.

Objectives: Significant literature exists on the effects of medication adherence on reducing healthcare costs, but less is known about the effect of medication adherence among Medicare low-income subsidy (LIS) recipients. This study examined the effects of medication adherence on healthcare costs among LIS recipients with diabetes, hypertension, and/or heart failure. Methods: This retrospective study analyzed Medicare claims data (2012-2013) linked to the Area Health Resources Files. Using measures developed by the Pharmacy Quality Alliance, adherence to 11 medication classes was studied among patients with 7 possible combinations of the diseases mentioned. Adherence was measured in 8 categories of proportion of days covered (PDC): $95%, 90% to,95%, 85% to,90%, 80% to,85%, 75% to,80%, 50% to,75%, 25% to,50%, and,25%. Annual Medicare costs were compared across adherence categories. A generalized linear model was used to control for patient/community characteristics. Results: Among patients with only one disease, such as diabetes, patients with the lowest adherence (PDC, 25%) had $3152/year higher Medicare costs than patients with the highest adherence (PDC >= 95%; $11101 vs $7949; P < .05). The adjusted costs among patients with PDC < 25% was $1893 higher than patients with PDC >= 95% ($9919 vs $8026; P < .05). Among patients with multiple chronic conditions, patients' adherence to medications for fewer diseases had higher costs. Conclusions: Greater medication adherence is associated with lower Medicare costs in the Medicare LIS population. Future policy affecting the LIS program should encourage better medication adherence among patients with chronic diseases.