(HealthDay News) – Underlying provider integration in a given geographic region may drive the formation of Medicare accountable care organizations (ACOs), according to a study published in the October issue of Health Affairs.

David I. Auerbach, from the RAND Corporation in Boston, and colleagues examined where Medicare ACOs have formed and what regional factors are predictive of ACO formation.

The researchers found wide variation in ACO formation, with large areas such as the Northwest devoid of ACOs, and other areas such as the Northeast and Midwest dense with them. A greater fraction of hospital risk sharing (capitation), larger integrated hospital systems, and primary care physicians practicing in large groups were key regional factors associated with ACO formation. No association was seen between ACO formation and area income, Medicare per capita spending, Medicare Advantage enrollment rates, and physician density.

“Together, these results imply that underlying provider integration in a region may help drive the formation of ACOs,” the authors write.

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