(HealthDay News) — Early reductions in Medicare spending were seen for the first full year of Medicare Shared Savings Program (MSSP) contracts for 2012 Accountable Care Organization (ACO) entrants, according to a study published in the New England Journal of Medicine.

J. Michael McWilliams, MD, PhD, from Harvard Medical School in Boston, and colleagues used Medicare claims from 2009 through 2013 to compare changes in spending and in performance on quality measures from before the start of ACO contracts to after the start of the contracts (2012 and 2013 cohorts) and those served by non-ACO providers (control group). The 2012 and 2013 cohorts were analyzed separately.

The researchers found that the ACO cohorts and the control group had similar adjusted Medicare spending and spending trends during the precontract period. In 2013, the differential change in total adjusted annual spending was –$144 per beneficiary in the 2012 ACO cohort vs control (P=.02), representing a 1.4% saving. The 2013 ACO cohort had a −$3 saving per beneficiary compared with the control group (P=.96). 

Among the 2012 and 2013 MSSP entrants, estimated savings were consistently greater in independent primary care groups than in hospital-integrated groups (P=.005 for interaction).

“The first full year of MSSP contracts was associated with early reductions in Medicare spending among 2012 entrants but not among 2013 entrants,” the researchers wrote.


  1. McWilliams JM, Hatfield LA, Chernew ME, Landon BE, Schwartz AL. Early Performance of Accountable Care Organizations in Medicare. N Engl J Med. 2016. doi:10.1056/NEJMsa1600142.