Unintended Consequences of Increased Out-of-Pocket Costs During Medicare Coverage Gap on Anticoagulant Discontinuation and Stroke

Abstract

Introduction: This study aims to assess the risk of direct oral anticoagulant (DOAC) discontinuation among Medicare beneficiaries with non-valvular atrial fibrillation (NVAF) who reach the Medicare coverage gap stratified by low-income subsidy (LIS) status and the impact of DOAC discontinuation on rates of stroke and systemic embolism (SE) among beneficiaries with increased out-of-pocket (OOP) costs due to not receiving LIS. Methods: In this retrospective cohort study, Medicare claims data (2015–2020) were used to identify beneficiaries with NVAF who initiated rivaroxaban or apixaban and entered the coverage gap during ≥ 1 year. DOAC discontinuation rates during the coverage gap were stratified by receipt of Medicare Part D Low-Income Subsidy (LIS), a proxy for not experiencing increased OOP costs. Among non-LIS beneficiaries, incidence rates of stroke and SE during the subsequent 12 months were compared between beneficiaries who did and did not discontinue DOAC in the coverage gap. Results: Among 303,695 beneficiaries, mean age was 77.3 years, and 28% received LIS. After adjusting for baseline differences, non-LIS beneficiaries (N = 218,838) had 78% higher risk of discontinuing DOAC during the coverage gap vs. LIS recipients (adjusted hazard ratio [aHR], 1.78; 95% CI [1.73, 1.82]). Among non-LIS beneficiaries, DOAC discontinuation during coverage gap (N = 91,397; 34%) was associated with 14% higher risk of experiencing stroke and SE during the subsequent 12 months (aHR, 1.14; 95% CI [1.08, 1.20]). Conclusion: Increased OOP costs during Medicare coverage gap were associated with higher risk of DOAC discontinuation, which in turn was associated with higher risk of stroke and SE among beneficiaries with NVAF.