The Impact of Medicare Part D on Medication Adherence Among Older Adults Enrolled in Medicare-Advantage Products

Background: Little is known about how Medicare Part D affects the medication refill adherence for cardiovascular and diabetes medications, particularly among beneficiaries without prior drug coverage. Objectives: To evaluate Medicare Part D's effect on medication adherence among beneficiaries with hyperlipidemia, hypertension, and/or diabetes enrolled in Medicare Advantage products. Research Design: We used a quasi-experimental pre-post design, with 3 treatment groups and a comparison group, to assess the effect of Part D on several measures of adherence to prescription medications. Subjects: Adults aged 65 or older with hyperlipidemia, hypertension, and/or diabetes in 2003 continuously enrolled between 2004 and 2007 in a large Pennsylvania insurer's Medicare Advantage products. Measures: Medication possession ratios (MPR), good adherence with MPR > 0.8, and intensity of treatment measured by average daily counts of pills per day of treatment. Results: Part D improved MPRs in the group without prior drug coverage by 13.4 percentage points (95% CI, 10.1-16.8), 17.9 (95% CI, 13.7-22.1), and 13.5 (95% CI, 11.5-15.5) for those with hyperlipidemia, diabetes, and hypertension, respectively. Adherence improved less in the other 2 groups with limited prior drug benefits. Although the proportion of beneficiaries in the intervention groups who attained good adherence levels increased after Part D, less than 50%, 68%, and 78% of beneficiaries with hyperlipidemia, diabetes, and hypertension, respectively, attained good adherence. Conclusion: Part D increased adherence to medications that reduce the risk of cardiovascular events for patients with hypertension, diabetes, and hyperlipidemia. This should improve the health of the elderly people in the long run.