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ACO Penetration Linked to Decreased Work Hours, Less Self-Employment


Accountable care organizations (ACOs), either directly or indirectly, are affecting physician employment patterns in regions where they have high penetration.

The passage of the Affordable Care Act has fueled the growth of accountable care organizations (ACOs), but little is known about how ACOs impact physician work hours and self-employment. A new study in JAMA Network Open suggests that ACOs have affected physician employment patterns.

Using data from the American Community Survey (ACS) for 2011 to 2015, researchers examined whether the increased number of ACOs impacted the number of hours physicians worked or if they were likely to be self-employed or employed by a hospital.

“The growth of ACOs has occurred unevenly across the country, with some hospital referral regions (HRRs) now having more than 20% of their population covered by ACOs and others having close to no ACO coverage,” the authors noted. “We compared physician work hours and self-employment between HRRs that have had more and less rapid growth of ACOs.”

According to the ACS data, in 2011, physicians worked a mean of 52.2 hours a week and one-fourth were self-employed, while 42% worked in a hospital. However, by 2015, physicians were working a mean of 51.9 hours and self-employment was down to 20.3% while employment by a hospital was up to 46.6%.

Read about how ACOs have improved quality over time.

The researchers found a 10-percentage point increase in ACO enrollment in the HRR in which a physician lived was associated with a decrease of 0.62 work hours per week. The association of ACO penetration on fewer work hours was more significant for men than women, and for younger physicians than older ones.

Although the decrease in work hours was not large, the authors suggested that the decrease may grow larger as ACOs become more mature and expand further. This is similar to how ACOs perform better the longer they are around and the more mature they are.

In addition, a 10-percentage point increase in ACO enrollment decreased the probability of a physician being self-employed. The decrease was more apparent among older physicians, and the association between ACO enrollment and being self-employed was not significant among women.

The authors noted some limitations to the study, such as the fact that the data only allowed them to know ACO penetration in the HRR where the physician lived and could not identify whether each physician actually worked in an ACO. But, it has been acknowledge that ACOs can have spillover effects, and the authors suggest ACO penetration may result in market-level changes affecting all physicians in an HRR, regardless of whether or not they work in an ACO.

“Given the wave of concern over physician burnout, it will be important to assess job satisfaction among physicians in ACOs to understand whether ACOs might help to alleviate some of the concerns currently besetting physicians,” the authors concluded. “Given the rapid increases in the numbers of primary care nurse practitioners, future research should also examine the association between ACOs and employment patterns of these nonphysician clinicians.”


Mahajan A, Skinner L, Auerbach DI, Buerhaus PI, Staiger DO. Association between the growth of accountable care organizations and physician work hours and self-employment. JAMA Network Open. 2018;1(3):e180876. doi:10.1001/jamanetworkopen.2018.0876.

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