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Background: Health care providers who participate as an accountable care organization (ACO) in the voluntary Medicare Shared Savings Program (MSSP) have incentives to lower spending for Medicare patients while achieving high performance on a set of quality measures. Little is known about the extent to which early savings achieved by ACOs in the program have grown and been replicated by ACOs that entered the program in later years. ACOs that are physician groups have stronger incentives to lower spending than hospital-integrated ACOs.Methods: Using fee-for-service Medicare claims from 2009 through 2015, we performed difference-in-differences analyses to compare changes in Medicare spending for patients in ACOs before and after entry into the MSSP with concurrent changes in spending for local patients served by providers not participating in the MSSP (control group). We estimated differential changes (i.e., the between-group difference in the change from the pre-entry period) separately for hospital-integrated ACOs and physician-group ACOs that entered the MSSP in 2012, 2013, or 2014.Results: MSSP participation was associated with differential spending reductions in physician-group ACOs. These reductions grew with longer participation in the program and were significantly greater than the reductions in hospital-integrated ACOs. By 2015, the mean differential change in per-patient Medicare spending was -$474 (-4.9% of the pre-entry mean, P<0.001) for physician-group ACOs that entered in 2012, -$342 (-3.5% of the pre-entry mean, P<0.001) for those that entered in 2013, and -$156 (-1.6% of the pre-entry mean, P=0.009) for those that entered in 2014. The corresponding differential changes for hospital-integrated ACOs were -$169 (P=0.005), -$18 (P=0.78), and $88 (P=0.14), which were significantly lower than for physician-group ACOs (P<0.001). Spending reductions in physician-group ACOs constituted a net savings to Medicare of $256.4 million in 2015, whereas spending reductions in hospital-integrated ACOs were offset by bonus payments.Conclusions: After 3 years of the MSSP, participation in shared-savings contracts by physician groups was associated with savings for Medicare that grew over the study period, whereas hospital-integrated ACOs did not produce savings (on average) during the same period. (Funded by the National Institute on Aging.). [ABSTRACT FROM AUTHOR]

Background: In the Medicare Shared Savings Program (MSSP), accountable care organizations (ACOs) have financial incentives to lower spending and improve quality. We used quasi-experimental methods to assess the early performance of MSSP ACOs.Methods: Using Medicare claims from 2009 through 2013 and a difference-in-differences design, we compared changes in spending and in performance on quality measures from before the start of ACO contracts to after the start of the contracts between beneficiaries served by the 220 ACOs entering the MSSP in mid-2012 (2012 ACO cohort) or January 2013 (2013 ACO cohort) and those served by non-ACO providers (control group), with adjustment for geographic area and beneficiary characteristics. We analyzed the 2012 and 2013 ACO cohorts separately because entry time could reflect the capacity of an ACO to achieve savings. We compared ACO savings according to organizational structure, baseline spending, and concurrent ACO contracting with commercial insurers.Results: Adjusted Medicare spending and spending trends were similar in the ACO cohorts and the control group during the precontract period. In 2013, the differential change (i.e., the between-group difference in the change from the precontract period) in total adjusted annual spending was -$144 per beneficiary in the 2012 ACO cohort as compared with the control group (P=0.02), consistent with a 1.4% savings, but only -$3 per beneficiary in the 2013 ACO cohort as compared with the control group (P=0.96). Estimated savings were consistently greater in independent primary care groups than in hospital-integrated groups among 2012 and 2013 MSSP entrants (P=0.005 for interaction). MSSP contracts were associated with improved performance on some quality measures and unchanged performance on others.Conclusions: The first full year of MSSP contracts was associated with early reductions in Medicare spending among 2012 entrants but not among 2013 entrants. Savings were greater in independent primary care groups than in hospital-integrated groups. [ABSTRACT FROM AUTHOR]