AIMS: To assess associations between out-of-pocket (OOP) expenditures and adherence to glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter-2 inhibitors (SGLT2i) among low-income Medicare beneficiaries with diabetes.
MATERIALS AND METHODS: We analysed Medicare Current Beneficiary Survey two-year longitudinal data (2016-2021) on beneficiaries with diabetes using GLP-1RAs (N = 168; weighted = 2 187 500) or SGLT2i (N = 139; weighted = 1 741 910) in year one (baseline). Among these, N = 97 (weighted = 1 117 637) GLP-1RA and N = 73 (weighted = 785 301) SGLT2i users had an income below 200% of the Federal Poverty Level (low-income). Survey-weighted generalized Poisson regression assessed the association between baseline cumulative OOP drug expenses and year two adherence, defined as proportion of days covered (PDC). We repeated analyses in participants with higher income and using dual (Medicare/Medicaid) enrolment as a proxy for full coverage in low income.
RESULTS: Year-two PDC was 65.2% (95% CI: 57.9%-72.6%) for low-income GLP-1RA users and 65.4% (95% CI: 58.3%-72.5%) for low-income SGLT2i users. We did not observe a significant association between OOP costs (mean: $253; range: $0-$4699) and adherence in low-income GLP-1RA users. For low-income SGLT2i users, higher OOP costs (mean: $204; $0-$2649) were associated with lower adherence: adjusted adherence ratio 0.959 (95% CI: 0.932-0.987) per $100 increase. Dual Medicare-Medicaid coverage was associated with increased adherence: adjusted adherence ratio 1.580 (95% CI: 1.061-2.352). For high-income GLP-1RA users, higher OOP expenditures were associated with increased adherence in the highest income range.
CONCLUSIONS: OOP costs for GLP-1RAs and SGLT2i are substantial, potentially posing a particular burden for low-income Medicare beneficiaries. Policy changes may reduce this burden, although adherence improvements appear limited to beneficiaries using SGLT2i.
