Objective: To evaluate the effect of Medicare Shared Savings Program accountable care organizations (ACOs) on hospital readmission after common surgical procedures.
Summary background data: Hospital readmissions following surgery lead to worse patient outcomes and wasteful spending. ACOs, and their associated hospitals, have strong incentives to reduce readmissions from 2 distinct Centers for Medicare and Medicaid Services policies.
Methods: We performed a retrospective cohort study using a 20% national Medicare sample to identify beneficiaries undergoing 1 of 7 common surgical procedures-abdominal aortic aneurysm repair, colectomy, cystectomy, prostatectomy, lung resection, total knee arthroplasty, and total hip arthroplasty-between 2010 and 2014. The primary outcome was 30-day risk-adjusted readmission rate. We performed difference-in-differences analyses using multilevel logistic regression models to quantify the effect of hospital ACO affiliation on readmissions following these procedures.
Results: Patients underwent a procedure at one of 2974 hospitals, of which 389 were ACO affiliated. The 30-day risk-adjusted readmission rate decreased from 8.4% (95% CI, 8.1-8.7%) to 7.0% (95% CI, 6.7-7.3%) for ACO affiliated hospitals (P < 0.001) and from 7.9% (95% CI, 7.8-8.0%) to 7.1% (95% CI, 6.9-7.2%) for non-ACO hospitals (P < 0.001). The difference-in-differences of the 2 trends demonstrated an additional 0.52% (95% CI, 0.97-0.078%) absolute reduction in readmissions at ACO hospitals (P = 0.021), which would translate to 4410 hospitalizations avoided.
Conclusion: Readmissions following common procedures decreased significantly from 2010 to 2014. Hospital affiliation with Shared Savings ACOs was associated with significant additional reductions in readmissions. This emphasis on readmission reduction is 1 mechanism through which ACOs improve value in a surgical population.