The Impact of Health Insurer Acquisitions of Physician Practices on Prices and Patient Visits.

Objective: To investigate whether the acquisition of physician practices by Optum, a subsidiary of United Health Group (UHG), influences patient volume and service prices, particularly, for patients enrolled in health insurance plans competing with UHG.

Study setting and design: We employed a novel database cataloging health insurer acquisitions of physician practices to identify those acquired by Optum-the nation's largest payvider (vertically integrated payer-provider)-from 2007 to 2023. These data were integrated with non-UHG commercial health insurance claims for practices acquired between 2015 and 2019. Using a stacked difference-in-differences design, we analyzed relative changes in prices and office visits across 12 Optum-acquired practices compared to a control group. Adjustments were made for physician profiles, practice characteristics, and calendar-year fixed effects to ensure robust estimates.

Principal findings: From 2007 to 2023, Optum acquired 44 physician practices, employing 7828 physicians by 2023. Postacquisition, we found no statistically significant average change in prices for most acquired practices relative to controls. However, the single largest acquisition was associated with a relative price increase of 4.5% (95% CI: [1.2%, 7.8%]; p = 0.02) for established patient visits. Preacquisition trends showed prices at acquired practices rising faster than controls. Additionally, Optum acquisitions were linked to suggestive declines in claim volume 1-1.5 years postacquisition, though this shift was predominantly driven by the largest acquired practice, indicating variability in outcomes across the sample.

Conclusions: Optum's acquisition of physician practices did not broadly result in significant price changes for evaluation and management services provided to patients with competing insurance plans, despite higher baseline prices at acquired practices. Suggestive reductions in patient volume emerged postacquisition, but effects were inconsistent. Extended follow-up research is warranted to evaluate whether these acquisitions reshape local healthcare market dynamics over time.