Year 1 of Medicare's Accountable Care Organization Realizing Equity, Access, and Community Health Model.

Importance: The US Centers for Medicare & Medicaid Services launched the Accountable Care Organization (ACO) Realizing Equity, Access, and Community Health (REACH) payment model in January 2023. In contrast to prior ACO initiatives, such as the Medicare Shared Savings Program (MSSP), ACO REACH includes equity-focused measures and payment adjustments, including an equity plan and financial risk adjustment for ACOs with higher proportions of underserved beneficiaries. However, it is unknown whether these changes have incented participation from organizations that serve beneficiaries from marginalized communities. Objective: To compare characteristics between participants in ACO REACH with those in MSSP and the broader pool of Medicare beneficiaries, organizations, and clinicians. Design, Setting, and Participants: This cross-sectional study included all Medicare beneficiaries clinicians, and ACOs enrolled in fee-for-service Medicare, MSSP, and ACO REACH from January 2022 to January 2023. Exposure: Enrollment in fee-for-service Medicare, MSSP, or ACO REACH. Main Outcomes and Measures: Beneficiary, clinician, and ACO characteristics. Results: In 2023, among 35 801 118 beneficiaries in the overall fee-for-service Medicare program, 18 911 213 (52.8%) were female, and 163 706 (0.5%) were American Indian or Alaska Native, 1 251 553 (3.5%) were Asian or Pacific Islander, 2 952 244 (8.2%) were Black, 2 396 771 (6.7%) were Hispanic, 27 642 765 (77.2%) were White, and 1 394 079 (3.9%) were another race (includes individuals who did not identify with a listed race, including those who self-identified as multiracial) or unknown race. A total of 1 958 881 beneficiaries were attributed to ACO REACH, and 11 340 987 were attributed to MSSP. A total of 132 ACOs participated in ACO REACH, while 456 ACOs participated in the MSSP. Compared with Medicare beneficiaries overall, REACH beneficiaries were older (85 years or older: 14.2% vs 10.3%; standardized mean difference [SMD], 0.44) and more often White (80.2% vs 77.2%) and less often Black (5.9% vs 8.2%) or Hispanic (5.8% vs 6.7%) (SMD, 0.24). REACH beneficiaries were slightly less likely to have Medicare entitlement due to disability (15.2% vs 17.6%) or be dually enrolled (15.1% vs 15.8%) (SMD, 0.07). REACH beneficiaries were less likely to be rural (3.9% vs 8.4%; SMD, 0.19) and less likely to reside in highly vulnerable geographic areas based on the Social Vulnerability Index (27.7% vs 29.4%; SMD, 0.08) compared with beneficiaries overall. Conclusions and Relevance: These findings suggest that, in its first year, ACO REACH did not achieve its goal of enrolling organizations that serve beneficiaries with high levels of social risk. Without broader participation, ACO REACH is unlikely to achieve its goal of reducing health inequities.