The challenge of attribution: responsibility for population health in the context of accountable care.

One of the three goals for accountable care organizations is to improve population health. This will require that accountable care organizations bridge the schism between clinical care and public health. But do healthcare delivery organizations and public health agencies share a concept of “population”? The authors think not: whereas delivery systems define populations in terms of people receiving care, public health agencies typically measure health on the basis of geography. This creates an attribution problem, particularly in large urban centers, where multiple healthcare providers often serve any given neighborhood. The current paper makes suggestions for potential innovations that could allow urban accountable care organizations to accept accountability, and rewards, for measurably improving population health. The U.S. has the highest per capita investment in health care of any nation in the world,1 but the health of Americans is poorer than that of people in other industrialized nations. The U.S. ranks 36th for life expectancy and 39th for infant mortality,2 and has a higher diabetes prevalence than any country in Western Europe.3 Improving health in America will require a greater emphasis on public health programming because the delivery of medical care, which consumes most health-related spending, has a relatively modest impact on population-level measures of mortality.4,5 As it happens, the U.S. in the midst of reforming its healthcare financing and delivery system. Does this afford an opportunity to improve population health? A central instrument of reform is accountable care contracting, which occurs when a healthcare payer forms an agreement with an incorporated group of healthcare providers, called an accountable care organization (ACO), that commits to delivering an integrated range of healthcare services including prevention, care coordination, and disease management. The Patient Protection and Affordable Care Act6 authorizes the Centers for Medicare and Medicaid Services (CMS) to issue accountable care contracts to providers caring for Medicare beneficiaries. Patients will be retrospectively assigned to an ACO based on their history of health services utilization, such that participation in a particular ACO would reflect choices an individual has already been making regarding where they seek their care.7 An accountable care contract has the potential to align financial incentives across a system of care such that quality outcomes improve and reductions are achieved in unnecessary procedures and preventable hospitalizations. If the overall cost of care for an ACO’s patients decreases, and quality benchmarks are met, the ACO shares in the savings. In some models, the ACO may also bear financial risk if targets are not achieved.8 The primary goals of the Medicare ACO program are to reduce fragmentation of care, reduce healthcare costs, and improve population health. In some rural or suburban areas where a single ACO may be dominant, the ACO’s prevention and disease management efforts might naturally align with population health improvement programs being implemented and measured by local health departments. However, in the complex urban areas that collectively contain 80% of the U.S. population, it has been found that population-level interventions undertaken by ACOs for their patients are unlikely to align with those of public health agencies in a geographic community.9