Trends in High-Severity Billing of Hospitalized Medicare Beneficiaries Treated by Hospitalists vs Nonhospitalists.

Importance: As US hospital expenditures continue to rise, understanding drivers of high-severity billing for hospitalized patients among inpatient physicians is critically important. Objective: To evaluate high-severity billing trends of Medicare beneficiaries treated by hospitalists vs nonhospitalists. Design Setting and Participants: This cohort study used Medicare fee-for-service claims of hospitalized patients from 2009 through 2018 to compare the proportion of high-severity billing between general medicine physicians classified as hospitalists vs nonhospitalists across initial, subsequent, and discharge hospital encounters. We compared physicians within the same hospital using hospital fixed effects and adjusted for patient demographics and comorbidities. Changes in the billing practices were assessed by investigating differences in slopes using an interaction term between physician type and time. Analyses were conducted between August 2021 and January 2022. Exposures: Treatment by hospitalists vs nonhospitalists. Main Outcomes and Measures: High-severity billing for initial, subsequent, and discharge hospital encounters. Results: The sample included 3 121 260 and 1 855 678 Medicare beneficiaries treated by hospitalists vs nonhospitalists, respectively. In each year, mean age, proportion female, proportion Black and Hispanic dual status, and mean number of chronic conditions were similar among those treated by hospitalists vs nonhospitalists (standardized mean difference < .01). The number of hospitalists grew by 76%, from 23 390 in 2009 to 41 084 in 2018, whereas nonhospitalists decreased by 43.6% (53 758 to 30 289). The proportion of encounters performed by hospitalists increased for the initial hospital encounters (46.3% to 76%), subsequent encounters (46.8% to 76.7%), and discharge encounters (46.1% to 78.5%) over the 10-year period. The proportion of high-severity billing across the hospital, subsequent, and discharge encounters was consistently higher among hospitalists relative to nonhospitalists across all years. Compared with the trends for nonhospitalists, the proportion of high-severity billing grew by 0.46% per year (95% CI, 0.44% to 0.49%; Conclusions and Relevance: In this cohort study of Medicare fee-for-service beneficiaries treated in hospitals, high-severity billing increased over time for hospital encounters at higher rates for hospitalists than for nonhospitalists. These differences do not appear to be explained by patient complexity. The increase in the number of hospitalists over time may be contributing to rising national costs related to hospital care.