Hou Yucheng, Domino Marisa Elena, Lewis Valerie A, Gong Qing, Callison Kevin, Trogdon Justin G
Department of Management, Policy and Community Health, School of Public Health, The University of Texas Health Science Center at Houston, Houston.
Center for Health Information and Research, College of Health Solutions, Arizona State University, Phoenix.
JAMA Netw Open. 2025 Feb 3;8(2):e2458311. doi: 10.1001/jamanetworkopen.2024.58311.
Accountable care organizations (ACOs) under the Medicare Shared Savings Program have long been envisioned as a pathway to improved care efficiency and quality of care for all Medicare beneficiaries. However, little is known about whether the changes in health care spending associated with ACOs have extended beyond ACO-attributed Medicare beneficiaries to all Medicare beneficiaries.
To estimate spending changes by non-ACO-attributed Medicare beneficiaries after moving to geographic areas with greater ACO participation.
DESIGN, SETTING, AND PARTICIPANTS: This repeated cross-sectional study analyzed claims from a 20% representative sample of all Medicare beneficiaries, aged 65 to 99 years, from 2009 to 2017. The sample consisted of Medicare beneficiaries who were never attributed to an ACO and moved once across hospital service areas (HSAs) during the study period (movers) and was supplemented by a 20% random sample of beneficiaries who never moved (nonmovers). Data analysis took place from November 2022 to October 2024.
Changes in the ACO market penetration rate triggered by nonattributed Medicare beneficiaries moving across HSAs.
Annual standardized Medicare spending per beneficiary on acute inpatient, outpatient facility, physician services, and total acute care as well as on hospital outpatient department, evaluation and management, and nonadmitted emergency department visits.
The estimation sample included 62 618 movers (388 263 beneficiary-years; mean [SD] age, 75 [7] years; 134 503 [65%] female-years) and 433 298 nonmovers (2 066 404 beneficiary-years; mean [SD] age, 76 [8] years; 1 273 154 [62%] female-years). In the base model, moving into a market with a 1-SD higher ACO penetration was associated with a 5.8% (95% CI, 4.1%-7.4%) decrease in spending on outpatient facilities and with a 1.6% (95% CI, 0.9% to 2.2%) increase in spending on physician services. Limited changes in total spending on acute inpatient and total acute care were found. These estimated changes were robust to controlling for a rich set of patient- and market-level characteristics and origin-destination HSA combinations.
This study provided novel evidence of market-level ACO spillovers to non-ACO-attributed Medicare beneficiaries. Although no substantial ACO spillovers in total acute care spending occurred, the substitution in spending on outpatient facility and physician services suggested that outpatient care may shift away from higher-cost facility settings for all Medicare beneficiaries in markets with greater ACO penetration.
长期以来，医疗保险共同储蓄计划下的 accountable care organizations（ACO）一直被视为提高所有医疗保险受益人的医疗效率和医疗质量的途径。然而，对于与 ACO 相关的医疗保健支出变化是否已从 ACO 所属的医疗保险受益人扩展到所有医疗保险受益人，人们知之甚少。
估计非 ACO 所属的医疗保险受益人在迁移到 ACO 参与度更高的地理区域后的支出变化。
设计、设置和参与者：这项重复横断面研究分析了 2009 年至 2017 年所有 65 至 99 岁医疗保险受益人的 20%代表性样本的索赔数据。样本包括在研究期间从未被归为 ACO 且曾在医院服务区（HSA）之间迁移一次的医疗保险受益人（迁移者），并补充了 20%从未迁移的受益人的随机样本（非迁移者）。数据分析于 2022 年 11 月至 2024 年 10 月进行。
非所属医疗保险受益人跨 HSA 迁移引发的 ACO 市场渗透率变化。
每位受益人在急性住院、门诊设施、医生服务以及总急性护理方面的年度标准化医疗保险支出，以及在医院门诊部、评估和管理以及未住院急诊科就诊方面的支出。
估计样本包括 62618 名迁移者（388263 受益人年；平均[标准差]年龄，75[7]岁；134503[65%]女性年）和 433298 名非迁移者（2066404 受益人年；平均[标准差]年龄，76[8]岁；1273154[62%]女性年）。在基础模型中，迁移到 ACO 渗透率高出 1 个标准差的市场与门诊设施支出下降 5.8%（95%CI，4.1%-7.4%）以及医生服务支出增加 1.6%（95%CI，0.9%至 2.2%）相关。在急性住院和总急性护理的总支出方面发现变化有限。这些估计变化在控制了丰富的患者和市场层面特征以及出发地 - 目的地 HSA 组合后是稳健的。
本研究提供了市场层面 ACO 对非 ACO 所属医疗保险受益人产生溢出效应的新证据。尽管在总急性护理支出方面没有出现实质性的 ACO 溢出效应，但门诊设施和医生服务支出的替代表明，在 ACO 渗透率更高的市场中，所有医疗保险受益人的门诊护理可能会从成本更高的设施环境中转移出来。
