Topics in Medicare Prescription Drug Enrollment in the Low-Income Subsidy Population

Abstract

In Medicare Part D, random assignment and potential yearly reassignment to premium-free stand-alone prescription drug plans (PDPs) is the default plan enrollment option for low-income subsidy (LIS) recipients. Randomization can cause medication access issues, but the impacts on medication use remain unclear because those who choose plans have not been separately examined. Medicare Advantage prescription drug plans (MAPDs) and tailored dual eligible Special Needs Plans (D-SNPs) have financial incentives to improve the medication adherence of Medicare-Medicaid dual eligibles compared to Medicare fee-for-service (FFS), but this relationship has not been assessed. The study used 2006-2009 Medicare administrative data and a customized dataset that differentiated plan election types. In aim 1, 29,784 LIS recipients assigned in 2007 were followed for three years and only 26% became choosers, with half selecting MA plans. PDP choosers appeared sicker and had higher Part D costs than non-choosers. In contrast, MA enrollees had fewer chronic conditions and lower costs than non-choosers. Choosers' plans covered more drugs than non-choosers' plans. In aim 2, medication use and costs were compared among 28,610 statin users who either accepted or opted out of reassignment. Cross-sectional and difference-in-differences (DID) regression models examined changes in statin use and costs. Compared to reassignees, the 7.6% who opted out were less likely to discontinue (-0.8%) and switch statins (-7.0%) and exhibited relative increases over time in brand name use (6.8%) and 30-day fill costs to Medicare ($2.82) and plans ($3.23). In aim 3, drug adherence with statins and angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (ACEIs/ARBs) was compared for samples of dual eligibles enrolled in FFS, MAPDs, and D-SNPs over 24 months, including subsamples who switched from FFS to managed care. Analyses included cross-sectional and DID regressions. Drug adherence was slightly higher among managed care dual eligibles when compared to FFS dual eligibles, but a percentage of those switching from FFS experienced disruptions in use. In conclusion, few randomized LIS recipients choose their own plans. Opting out of reassignment has minimal impact on statin adherence and costs. Additional safeguard policies are needed for dual eligibles switching from FFS to Medicare managed care.