While the consolidation trend across healthcare accelerated after the Affordable Care Act (ACA) was passed, there's little evidence connecting consolidation to providers wanting to succeed under accountable care organization (ACO) programs created after the ACA, according to a study published in the February issue of Health Affairs.

Harvard University PhD candidate Hannah Nephrash and her coauthors said there was “widespread concern” the expansion of these new payment models would lead to greater consolidation, with the assumption being larger organizations can bear more risk in ACO contracts. The study argued empirical evidence to back up these worries does not exist.

It offered two complementary analyses: 1) comparing consolidation over time between markets with more ACO contracting in 2014 versus less, and 2) within markets between ACO-contracting physicians and those not participating in an ACO. Nephrash and her coauthors examined a variety of data, including Medicare claims, publicly-announced data on hospital mergers and acquisitions of physician practices, and American Hospital Association surveys from 2008 to 2015.

The results confirmed physician groups and hospital systems got larger after the ACA was signed into law. That consolidation trend, however, wasn’t driven by a desire to take on more financial risk in ACO contracts.

“Markets with greater 2014 ACO participation did not experience differential changes in physician-hospital integration, physician group size, physician market concentration, hospital market concentration or, importantly, commercial health care prices from 2008 to 2013,” Nephrash and her coauthors wrote.

There was some evidence, however, of defensive consolidation.  The study found an overall increase in post-ACA hospital mergers without changes in hospital market concentration related to ACO penetration, and “a significant inverse relationship” between pre-ACA hospital market concentration and post-ACA penetration of ACOs. This means practices and hospitals may have consolidated to avoid entering into risk contracts, not to succeed in them.

“Hospitals and specialists in particular might consolidate to rebuff payer pressure to enter risk contracts or to attain sufficient market share to ensure continued referrals from ACOs that might otherwise steer patients to more efficient providers,” Nephrash and her coauthors wrote.