Associations Between Annual Medicare Part D Low-Income Subsidy Loss and Prescription Drug Spending and Use.

Importance: The Medicare Part D Low Income Subsidy (LIS) program provides millions of beneficiaries with drug plan premium and cost-sharing assistance. The extent to which LIS recipients experience subsidy losses with annual redetermination cycles and the resulting associations with prescription drug affordability and use are unknown. Objective: To examine how frequently annual LIS benefits are lost among Medicare Part D beneficiaries and how this is associated with prescription drug use and out-of-pocket costs. Design, Setting, and Participants: In this cohort study of Medicare Part D beneficiaries from 2007 to 2018, annual changes in LIS recipients among those automatically deemed eligible (eg, due to dual eligibility for Medicare and Medicaid) and nondeemed beneficiaries who must apply for LIS benefits were analyzed using Medicare enrollment and Part D event data. Subsidy losses were classified in 4 groups: temporary losses (<1 year); extended losses (≥1 year); subsidy reductions (change to partial LIS); and disenrollment from Medicare Part D after subsidy loss. Temporary losses could more likely represent subsidy losses among eligible beneficiaries. Multinomial logit models were used to examine associations between beneficiary characteristics and subsidy loss; linear regression models were used to compare changes in prescription drug cost and use in the months after subsidy losses vs before. Analyses were conducted between November 2022 and November 2023. Exposure: Subsidy loss at the beginning of each year among subsidy recipients in December of the prior year. Main Outcomes and Measures: The main outcomes were out-of-pocket costs and prescription drug fills overall and for 4 classes: antidiabetes, antilipid, antidepressant, and antipsychotic drugs. Results: In 2008, 731 070 full LIS beneficiaries (17%) were not deemed automatically eligible (39% were aged <65 years; 59% were female). Nearly all beneficiaries deemed automatically eligible (≥99%) retained the subsidy annually from 2007 to 2018, compared with 78% to 84% of nondeemed beneficiaries. Among nondeemed beneficiaries, disabled individuals younger than 65 years and racial and ethnic minority groups were more likely to have temporary subsidy losses vs none. Temporary losses were associated with an average 700% increase in out-of-pocket drug costs (+$52.72/mo [95% CI, 52.52-52.92]) and 15% reductions in prescription fills (-0.58 fills/mo [95% CI, -0.59 to -0.57]) overall. Similar changes were found for antidiabetes, antilipid, antidepressant, and antipsychotic prescription drug classes. Beneficiaries who retained their subsidy had few changes. Conclusions and Relevance: The conclusions of this cohort study suggest that efforts to help eligible beneficiaries retain Medicare Part D subsidies could improve drug affordability, treatment adherence, and reduce disparities in medication access.