Cost-Related Medication Nonadherence After the Inflation Reduction Act.

Importance: High prescription drug costs are a pressing national concern and contribute to medication nonadherence and poor health outcomes. The Inflation Reduction Act (IRA) introduced sweeping reforms to improve medication affordability, but their potential impact on medication adherence is unknown. Objective: To evaluate the association of the IRA's 2024 prescription drug provisions with cost-related medication nonadherence as well as health care-related financial strain. Design, Setting, and Participants: This quasi-experimental difference-in-differences analysis used data from the 2021-2024 National Health Interview Survey. Adults aged 62 to 67 years who were enrolled in Medicare Part D (intervention) or private insurance (comparator) were included. Individuals with incomes 135% or less of the federal poverty level, dually enrolled in Medicaid, and who currently used insulin were excluded from the primary analysis because preexisting protections limited their out-of-pocket spending in Medicare. Exposures: The IRA's prescription drug provisions were enacted on January 1, 2024, including (1) elimination of the 5% coinsurance requirement for catastrophic coverage that effectively capped out-of-pocket drug costs to approximately $3300 per year and (2) expansion of full low-income subsidies. Main Outcomes and Measures: The primary outcome was cost-related medication nonadherence. The secondary outcome was health care-related financial strain. Results: The study population included 1454 Medicare beneficiaries (weighted mean [SD] age, 66.1 [0.8] years; 53.1% female) and 3797 privately insured comparators (weighted mean [SD] age, 63.3 [1.2] years; 50.7% female). Prior to the 2024 IRA reforms, trends in cost-related medication nonadherence were parallel between the 2 groups. Following implementation of the IRA's 2024 provisions, cost-related medication nonadherence declined among Medicare beneficiaries relative to comparators (adjusted difference-in-differences estimate, -4.9 percentage points [pp]; 95% CI, -8.8 to -1.0 pp). Among Medicare beneficiaries with multiple chronic conditions, the decline was more pronounced (adjusted difference-in-differences estimate, -7.8 pp; 95% CI, -12.9 to -2.8 pp). These findings were robust across multiple sensitivity analyses as well as secondary analyses using Medicare beneficiaries with incomes 135% or less of the federal poverty level and dually enrolled in Medicaid as an alternative comparator group. In contrast, there were no meaningful differential changes observed for health care-related financial strain (adjusted difference-in-differences estimate, -2.6 pp; 95% CI, -10.1 to 5.0 pp). Conclusions and Relevance: In this difference-in-differences analysis, the IRA's 2024 prescription drug provisions were associated with a reduction in cost-related medication nonadherence among eligible Medicare beneficiaries in their first year. These early improvements may have important implications for chronic disease management and downstream clinical outcomes.