Highlights: https://innovation.cms.gov/innovation-models/aco-investment-model

·       Across a variety of metrics, AIM ACOs were located in areas of the nation with greater health care needs and less access to accountable care. With AIM, CMS successfully encouraged ACO formation in areas where ACOs may not have otherwise formed and where other Medicare payment and delivery innovations were less likely to be present. Indeed, many AIM ACOs indicated in interviews and surveys with ACO leadership that AIM funds provided them the ability to form an ACO and join the Shared Savings Program.

·       As of 2020, 14 of the initial 47 AIM ACOs (29.8 percent) remained in the Shared Savings Program. The majority of exiting ACOs did so at the end of 2018, after their required Shared Savings Program participation period to receive AIM funds concluded. ACOs remaining in the program were larger and served less rural markets. Nine AIM ACOs (19.1 percent) moved to a two-sided financial risk track by 2019; seven of them remained in the program as of 2020.

o   AIM ACO leadership decisions to exit the Shared Savings Program were tied to their perceived lack of readiness for financial risk-taking. If given the option, many AIM ACOs would have likely renewed in an upside-only risk track, where they would not be liable for paying back any spending above their benchmark. This likelihood was supported by ACOs in the Advanced Payment (AP) ACO Model, the predecessor model to AIM. After two years of AP funds, 50 percent of the AP ACOs remained in the Shared Savings Program in an upside-only risk track. Two-thirds of the remaining AP ACOs renewed with two-sided risk in 2019.

o   Twenty-nine AIM ACOs exited the Shared Savings Program after 2018, but more than 60 percent of participating providers of these exiting AIM ACOs joined other SSP ACOs by 2020.

·       AIM was associated with an estimated net aggregate reduction in total Medicare spending of $381.5M across the three AIM performance years among AIM ACOs targeting rural areas after accounting for Medicare’s payment of AIM funds and ACOs’ earned shared savings.

o   AIM ACOs targeting rural areas reduced per beneficiary per month (PBPM) total Medicare spending in each of the three AIM performance years. Estimated reductions were -$28.21 PBPM in PY1 (2016); -$36.94 PBPM in PY2 (2017); and -$38.73 in PY3 (2018). All estimates were statistically significant at the 5 percent level.

o   The estimated reductions in total Medicare spending were driven by reductions in utilization, most notably decreases in acute hospitalizations, emergency department visits, and days in skilled nursing facilities. These reductions were consistent across the performance years.

o   When comparing the performance of AIM ACOs to similar non-AIM SSP ACOs to examine the marginal effect of AIM funds, AIM ACOs showed no increases in spending or utilization.

·       AIM ACOs achieved reductions in total Medicare spending without sacrificing quality of patient or caregiver experience and quality of care. We found that AIM ACOs, even those reducing total Medicare spending, hospitalizations, and emergency department visits, maintained the quality of care provided.

·       AIM ACOs targeting rural areas were successful in reducing total Medicare spending across several key ACO attributes and no one factor appeared to be a consistent driver of differential reductions. There was some suggestive evidence that AIM ACOs with management company affiliations were able to achieve greater reductions sooner; that is, managed AIM ACOs may have reduced Medicare spending more than independent ACOs in 2016 and 2017, but in 2018, independent ACOs reduced Medicare spending by approximately the same amount as managed ACOs.