Abstract
<title>Abstract</title> <p>Importance: Where racial differences in 30‑day hernia surgery outcomes originate — in pre‑surgical health, the surgical episode, or downstream — is poorly characterized. Objective: To quantify the share of racial differences in 30‑day hernia repair outcomes statistically attributable to pre‑surgical comorbidity versus the share that remains unexplained. Design: Retrospective cohort study using ACS‑NSQIP Participant Use Files from January 1, 2008 through December 31, 2021. Setting: Multi‑institutional registry data from approximately 700 ACS‑NSQIP‑participating hospitals, primarily in the United States. Participants: Adults (≥18 years) undergoing hernia repair identified by standardized ICD‑9/10 diagnostic and CPT procedure codes. After exclusions for missing race, invalid coding, or extreme procedural complexity, 391,095 patients were retained. Exposures: Race per ACS‑NSQIP definitions: White (85.9%), Black or African American (11.5%), Asian (2.0%), American Indian or Alaska Native (0.5%), and Native Hawaiian or Pacific Islander (0.2%). Main Outcomes and Measures: Thirty‑day postoperative complications, including readmission, return to the operating room, surgical site infection, venous thromboembolism, transfusion, sepsis, and major medical complications. Each racial outcome gap was partitioned into a pre‑surgical comorbidity‑mediated ("explained") component and an unexplained residual using nonlinear (Fairlie) decomposition with bootstrap 95% confidence intervals. Results: Black patients had higher unadjusted complication rates (readmission OR 1.26); Asian patients had lower rates (superficial SSI OR 0.50). After Bayesian adjustment, race retained no independent risk‑increasing association. Fairlie decomposition: pre‑surgical comorbidity statistically accounted for the racial gap in pneumonia and organ‑space SSI in both groups, with no robust residual. For 30‑day readmission, comorbidity accounted for 45% of the Black–White gap (unexplained +0.41 pp, 95% CI [+0.21, +0.59]) and 57% of the Asian–White gap (unexplained −0.49 pp [−0.80, −0.17]). For Black–White differences in DVT, cardiac arrest, renal insufficiency, and unplanned reintubation, gaps were overwhelmingly unexplained by measured pre‑surgical characteristics. Conclusions and Relevance: Pre‑surgical comorbidity statistically accounted for many but not all racial differences in 30‑day hernia outcomes. Robust unexplained residuals remained for several outcomes, particularly 30‑day readmission and selected Black–White complications. The unexplained portion does not identify a specific mechanism. Equity‑focused interventions should target both pre‑surgical optimization and factors operating downstream of the surgical episode.</p>