Zero-Dollar Copayment Impact on Adherence Scores for Centers for Medicare and Medicaid Services Star Ratings Generic Medications

Introduction: The Centers for Medicare & Medicaid Services (CMS) Star Ratings system pushes Medicare Advantage health plans to achieve ever greater attainments in key metrics, including adherence to hydroxymethylglutaryl-CoA reductase inhibitor (statins), renin-angiotensin system (RAS) antagonist, and noninsulin antihyperglycemic (DM) medications. The purpose of this observational study was to evaluate the impact of expanding a $0 copayment (copay) benefit from mail order-only to mail order plus retail pharmacies on adherence to statin, RAS, and DM medications.

Methods: Medicare beneficiaries with and without a $0 copay expansion who received ≥ 1 dispensing of a generic, CMS Star Ratings RAS, statin, and/or DM medication during both 2021 and 2022 were included. Outcomes included changes in proportion of days covered (PDC) from 2021 to 2022 and proportions of patients with a PDC ≥ 0.8 in 2022.

Results: Overall (N = 65,716), patients had a high (> 0.930) mean baseline PDC. Patients with $0 copay expansion had a statistically significant greater mean PDC increase for statin (adjusted P = 0.038), reduction for RAS (adjusted P = 0.036), and no difference for DM (adjusted P = 0.696). Patients with a $0 copay expansion had statistically significant higher proportions of beneficiaries with a PDC ≥ 0.8 for statin (adjusted P = 0.003) and RAS (adjusted P = 0.003) but not DM (adjusted P = 0.256).

Discussion: An expanded $0 copay was associated with minor increased generic statin medication adherence.

Conclusion: In populations with a high baseline PDC, expanding a $0 copay benefit on generic statin, RAS, and DM medications to dispensing outside of mail order may only contribute slightly to an increase or sustainment of a health plan's CMS Star Ratings.