The Association Between Hospital Volume and In-Hospital Mortality in Severe Burn Patients: A Nationwide Study Using the Japanese Burn Registry

Evidence regarding the relationship between hospital volume and mortality in burn care remains inconclusive. Therefore, we investigated this association using a comprehensive, nationwide clinical registry with detailed clinical data in Japan. We conducted a retrospective multicenter cohort study using the Japanese Society of Burn Injuries Burn Registry 2011, including 24,065 burn patients hospitalized between 2011 and 2023. We included acute burn patients with a Burn Index ≥10 and excluded those admitted for reconstructive/aesthetic surgery, transferred in or out, presenting with cardiopulmonary arrest on arrival, or with missing key variables. The primary exposure variable was annualized hospital volume of burn admissions, categorized into quartiles. The primary outcome was in-hospital mortality. Adjusted odds ratios (aORs) were calculated using multivariable logistic regression with hospital-clustered robust standard errors, controlling for age, sex, burn size, full-thickness burns, inhalation injury, mechanism, anatomical site, and admission year. Secondary analyses were based on the annual surgical volume, and prespecified sensitivity analyses (tertiles, exclusion of the highest-volume hospital, length of stay ≥3 days, and inclusion of transfer-in cases) assessed the robustness. A total of 2,859 patients treated at 105 hospitals met eligibility criteria for primary analysis. Compared with the lowest-volume quartile (Q1), aORs (95% CI) for the mortality were Q2, 1.48 (0.83–2.66); Q3, 1.05 (0.59–1.90); Q4, 1.13 (0.66–1.95); p for trend 0.65. Using surgical volume quartiles, aORs were Q2, 0.81 (0.42–1.56); Q3, 1.05 (0.55–2.02); Q4, 0.73 (0.38–1.42); p for trend 0.30. Sensitivity analyses yielded consistently null findings. In this nationwide registry, we did not find evidence that higher hospital admission rates or surgical volume were associated with in-hospital mortality after risk adjustment. In Japan’s current system, volume alone may not confer a survival advantage. • ・Nationwide registry study of severe burn outcomes by hospital volume in Japan • ・No clear association between hospital volume and in-hospital mortality • ・Standardized burn care protocols may reduce volume-outcome differences • ・Hospital volume alone may not provide a survival advantage