Physician Composition of Hospitals' Workforce and Mortality Across US Hospitals: A Cross-Sectional Study.

BACKGROUND: The inpatient clinical workforce in US hospitals is evolving, with advanced practice practitioners-nurse practitioners and physician assistants-playing increasingly prominent roles. The relationship between hospital clinician mix and patient mortality remains unclear. Our objective was to examine the association between hospital-level physician proportion and 30-day risk-standardized mortality rates (RSMRs) for common inpatient conditions. METHODS: We conducted a cross-sectional national study of US hospitals treating Medicare fee-for-service beneficiaries in 2022. Medicare and American Hospital Association datasets were linked at the hospital level. The hospital-level exposure was the physician proportion, defined as affiliated physicians divided by total affiliated physicians and advanced practice practitioners. Outcomes were hospital-level RSMRs for acute myocardial infarction, coronary artery bypass graft surgery, chronic obstructive pulmonary disease, heart failure, pneumonia, and stroke. RESULTS: Among 3487 hospitals, the mean physician proportion was 79.7% (standard deviation, 9.4%), ranging from 67.8% in the lowest quartile to 91.6% in the highest. Hospitals in the highest physician proportion quartile (Q4) had lower RSMRs than hospitals in the lowest quartile (Q1) for all conditions-acute myocardial infarction (12.54 versus 12.86; P < 0.001), coronary artery bypass graft (2.92 versus 3.05; P = 0.106), chronic obstructive pulmonary disease (9.11 versus 9.83; P < 0.001), heart failure (11.24 versus 12.73; P < 0.001), pneumonia (17.51 versus 18.64; P < 0.001), and stroke (13.41 versus 14.31; P < 0.001). Weighted multivariable models identified significant inverse associations between physician proportion and RSMRs. CONCLUSIONS: Greater physician representation was associated with lower hospital-level mortality across common and high-burden medical conditions, indicating workforce composition may be an important determinant of hospital quality.