Association Between the Growth of Accountable Care Organizations and Physician Work Hours and Self-employment

The share of the population covered by accountable care organizations (ACOs) is growing, but the association between this increase and physician employment is unknown.

To investigate the association between the growth of ACOs and changes in physician work hours, probability of being self-employed, and probability of working in a hospital.

A fixed-effects design was used in this cross-sectional study to compare changes in physician employment in hospital referral regions with high vs low ACO growth. A nationally representative 1% sample of all working US physicians obtained annually from 2011 through 2015 from the American Community Survey (N = 49 582) was included. Data analysis was conducted from March 28, 2017, to April 10, 2018.

Physician hours worked per week, probability of being self-employed, and probability of working in a hospital.

Of the 49 582 physicians included in the study, 63.5% were men; the mean (SD) age of sampled physicians was 46.01 (11.59) years. In 2011, sampled physicians worked a mean (SD) of 52.2 (16.1) hours per week, 24.43% were self-employed, and 42.03% worked in a hospital. A 10-percentage point increase in ACO enrollment in a hospital referral region was associated with a statistically significant reduction of 0.82 (95% CI, -1.52 to -0.13; P = .02) work hours in men and a decrease of 2% (95% CI, -3.8% to -0.1%; P = .04) in the probability of all physicians being self-employed. The association with self-employment was strongest (-5.0%; 95% CI, -8.7% to -1.4%; P = .006) in physicians aged 50 to 69 years, who were also more likely (4.0%; 95% CI, 1.0% to 6.9%; P = .009) to work in a hospital.

The growth of ACOs within hospital referral regions appears to be associated with a reduction in hours of work and self-employment among physicians. These results suggest that ACOs may affect physician employment patterns.