2025 ACO Publications

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ACO Research Summary: January 2025 

‘On the OB Side of Things, It’s Completely Disconnected’: Early Implementation of Medicaid Accountable Care Organizations and Health Care in the Perinatal Period
Date: February 1, 2025
Source: Women’s Health Issues
Article
This study examined how individuals in ACO leadership have approached program design to address maternal health and how these programs have shaped health care utilization and maternal health from the perspective of postpartum ACO beneficiaries and clinicians. Researchers conducted virtual semi-structured interviews with three key stakeholder groups in Massachusetts (ACO leaders, maternity care clinicians, and Medicaid ACO members who had given birth within the past 6–24 months) between November 2021 and May 2023. Thirty-three interviews were conducted: four with ACO leaders, 15 with maternity care clinicians, and 14 with ACO members. Maternity care clinicians did not perceive that ACO implementation had substantially impacted perinatal health care. Interviews with ACO leadership suggested that the lack of perceived impact may be partially explained by competing priorities; the Massachusetts Medicaid ACOs generally did not focus on maternal health during the initial implementation period. Postpartum ACO members were largely unaware of ACOs. Lack of explicit attention to the perinatal population in Medicaid financing and delivery system reforms may reduce the potential impact in improving outcomes.

Accountable Care Organizations, Child Opportunity Index, and Complicated Appendicitis in Children
Date: February 2025
Source: Journal of Surgical Research
Article
This study examined the impact of ACO enrollment on the association of low scores on the Child Opportunity Index (COI) with the likelihood of a child having complicated appendicitis. Using a single-institution, retrospective review of children with public insurance undergoing appendectomy for acute appendicitis, COI and clinical confounders were compared by simple versus complicated appendicitis. Among 1,337 children, 31.0% had complicated appendicitis. Most (78.6%) were enrolled in the ACO; this was not different between simple and complicated appendicitis. As overall COI quintile decreased (lower opportunity), the percentage of children with complicated appendicitis increased. The association between COI and complicated appendicitis was not modified by ACO enrollment. COI and ACO enrollment were not associated with postoperative complications, except children in the ACO had fewer 30-day readmissions (4.2% versus 14.6%, P < 0.001) compared to those with other public insurance.

Future Of Accountable Care: Lessons Learned and Potential Paths Forward During A Time Of Transition
Date: January 31, 2025
Source: Health Affairs Forefront
Article
Accountable care is not at the top of the news, and, historically, the shift to paying for value has had bipartisan support, including across the prior Trump and Biden administrations. But accountable care itself is at an inflection point, more prevalent than ever but still an “alternative” to fee-for-service. Trump administration priorities related to preventing chronic disease complications and reducing federal spending could provide tailwinds for accountable care, but policy disruptions and uncertainty could create headwinds as well. This article examines the landscape during the transition when opportunities are emerging but by no means resolved.

The Spillover Effect of the CMS Innovation Center
Date: January 21, 2025
Source: NEJM Catalyst
Article
The models established by the CMS Innovation Center to reduce Medicare and Medicaid spending while maintaining or enhancing the quality of care—such as Bundled Payments for Care Improvement and Comprehensive Primary Care—affect the overall health care delivery system beyond participating organizations. This study, based on interviews with providers, payers, management services organizations, and industry and academic experts, examined the drivers of spillover effects from the CMS Innovation Center’s programs.

Improving CMS Financial Benchmarking: Lessons Learned by The Innovation Center
Date: January 16, 2025
Source: Health Affairs Forefront
Article
The CMS Innovation Center uses financial benchmarks as one of several mechanisms to incentivize model participants to reduce health care spending and establish performance thresholds. Financial benchmarks for model participants estimate the expected cost of included health care items and services for attributed individuals during a fixed performance period. CMS calculates financial benchmarks using expenditures from CMS claims data and frequently incorporates three elements: how much CMS has historically paid for the related health care item(s) and service(s), how payments might change, and the characteristics and health of the patients served by the model. The Innovation Center uses financial benchmarks in many models, for example, in the Accountable Care Organization Realizing Equity, Access, and Community Health (ACO REACH) Model, the Kidney Care Choices Model, and the newly announced Transforming Episode Accountability Model (TEAM) and States Advancing All-Payer Health Equity Approaches and Development (AHEAD) models. The Innovation Center is committed to an ongoing cycle of designing, refining, and testing new benchmarking methodologies, particularly as we learn from ongoing model tests. This article lays out the four principles and key considerations the Innovation Center uses when setting financial benchmarks for upcoming models.

Medicare Accountable Care Organizations In 2023: Large Savings With Increasing Value-Based Programmatic Competition
Date: January 15, 2025
Source: Health Affairs Forefront
Article
In late October 2024, CMS released data for the 11^th year of the ACO Medicare Shared Savings Program (MSSP), marking the seventh consecutive year that the MSSP has achieved savings for Medicare (based on comparisons to the administrative benchmark) and the largest savings in the program’s history. The number of participating ACOs decreased slightly from 2022 due to a confluence of factors, but as fewer beneficiaries enroll in traditional Medicare and alternative programs for ACOs such as the ACO Realizing Equity, Access, and Community Health (ACO REACH) Model, attribution in shared savings programs (SSPs) will be challenging. As always, comparisons against benchmarks, including quality, should be interpreted with caution given that savings are calculated from benchmarks set in advance based on a blend of historical and regional spending, the results are unadjusted, and more ACOs are claiming uncontrollable circumstance adjustments (often a function of natural disasters and other emergencies).

Key findings include:

• Non-dually enrolled beneficiaries presented higher risk scores and greater average net savings per capita compared to the dually enrolled population.
• Overall, 453 different organizations participated in the MSSP, a 6 percent decline from the previous year’s 482 participants. The total number of beneficiaries also declined by roughly 2 percent from 2022 to 2023.
• For the second year since the MSSP began, the majority of ACOs took downside risk: 67 percent of ACOs were two-sided risk, while 33 percent were upside only. ACOs in two-sided risk were nearly twice as likely to achieve shared savings than upside-only ACOs.
• In 2023, the ACOs in the MSSP produced more than $2.10 billion in net savings and generated $3.08 billion in savings compared to benchmarks, or $234 net savings per capita, a 22 percent increase in net savings per capita and almost double the net savings compared to benchmarks from 2022.
• Consistent with last year’s findings, ACOs with a larger share of participating primary care physicians were more likely to receive shared savings and higher net savings per capita.
• Non-dually enrolled beneficiaries presented higher risk scores and greater average net savings per capita compared to the dually enrolled population.

How Benchmark Changes Affect Participation in Accountable Care Organizations: Prospects for Voluntary Payment Models
Date: January 2025
Source: American Journal of Health Economics
Article
In voluntary alternative payment models, participation is essential for model viability and the progression of provider payment reform. This study examines participation decisions of ACOs in the Medicare Shared Savings Program. Researchers leveraged a natural experiment in which a 2017 rule change introduced differential shocks to an ACO’s baseline spending and performance-year spending. The net effect was an effective change in benchmarks that varied across ACOs. Dropout was 7 percentage points more likely among ACOs with effective benchmark decreases. While small reductions in the effective benchmark did not affect program participation, larger reductions increased dropout by 11 percentage points. ACOs with spending already above their benchmarks were particularly sensitive to effective benchmark reductions, consistent with the program’s weak long-term incentives to reduce spending. The results highlight the causal role benchmarks play in determining ACO participation and the need to consider the consequences of participation effects in the design of new payment models.

High-Intensity Home-Based Rehabilitation in a Medicare Accountable Care Organization
Date: January 8, 2025
Source: The American Journal of Managed Care
Article
Patients are often discharged to a skilled nursing facility (SNF) for postacute rehabilitation. Functional outcomes achieved in SNFs are variable, and costs are high. Especially for ACOs, home-based postacute rehabilitation offers a high-value option if outcomes are not compromised. This study compared outcomes for episodes in a novel high-intensity home-based rehabilitation (HIHR) model vs a SNF. Medicare patients from a large integrated multihospital health system who had low to moderate medical complexity and mild to moderate mobility deficits at hospital discharge were included. The primary exposure was discharge to HIHR (intervention) or a SNF (control) after hospitalization. The primary outcome was Activity Measure for Post-Acute Care (AM-PAC) mobility score. Secondary outcomes were Medicare costs within 30 and 90 days post hospitalization, 30-day readmission rate, and index hospital length of stay (LOS). 

There were 171 patients discharged to HIHR and 841 to SNFs. The adjusted AM-PAC mobility T-score was 8.2 (95% CI, 6.3-10.1) points higher after HIHR vs. SNF. Adjusted Medicare costs were lower for the HIHR cohort (within 90 days, –$17,123; 95% CI, –$20,757 to –$13,490). Hospital LOS and odds for readmission did not differ between cohorts. The HIHR cohort demonstrated better functional outcomes and lower posthospital costs. HIHR may be a high-value option for patients attributed to a Medicare ACO who have moderate medical complexity and moderate functional deficits at the time of hospital discharge.

Association of Medicaid Accountable Care Organizations and Postpartum Mental Health Care Utilization
Date: January 7, 2025
Source: Health Services Research
Article
This study examined the association of Massachusetts Medicaid ACO implementation with changes in mental health care utilization in the postpartum period. The study examined care for people with a birth covered by Medicaid or private insurance and used a difference-in-differences design to compare differences before and after Medicaid ACO implementation for those with Medicaid versus those with private insurance. The primary outcome was a binary measure of having at least one outpatient mental health care visit in the 6 months postpartum. The study included 107,813 births (53.0% Medicaid, 47.0% private). About 8% of women had at least one outpatient mental health visit in the 6 months postpartum, with similar rates among those with Medicaid versus those with private insurance pre-ACO implementation (7.9% Medicaid versus 7.7% private). An increase in utilization among privately insured individuals and a decrease among Medicaid beneficiaries post-ACO implementation was observed. Regression-adjusted difference-in-differences estimates indicate that Medicaid ACO implementation was associated with a 1.3 percentage point [pp] decrease (95% confidence interval: 1.3 pp, −0.5 pp; p < 0.01) in the probability of having an outpatient mental health visit for those with Medicaid. Future research should determine whether this increased disparity in mental health care utilization persists with maturation of the ACO delivery model.

Use Of Patient Health Survey Data for Risk Adjustment to Limit Distortionary Coding Incentives in Medicare
Date: January 2025
Source: Health Affairs
Article
A core problem with the current risk-adjustment system in Medicare Advantage and ACO programs—the Hierarchical Condition Categories (HCC) model—is that the inputs (coded diagnoses) can be influenced for gain by risk-bearing plans or providers. Using existing survey data on health status (which provide less manipulable inputs), researchers found that the use of a hybrid risk score drawing from survey data and a scaled-back set of HCCs would, in addition to mitigating coding incentives, modestly lessen risk-selection incentives, strengthen payment incentives to deliver efficient care, allocate payment across ACOs more efficiently according to markers of population health that are not as affected by practice patterns or coding efforts, and redistribute payment in a manner that supports equity goals. Although sampling error and survey nonresponse present challenges, analyses suggest that these should not be prohibitive. Overall, this proof-of-concept analysis suggests that using survey data to improve risk-adjustment performance is a promising strategy that merits further development.