Outcomes and Risk Factors for In-Hospital Mortality in Mild-to-Moderate Trauma Patients: A Nationwide Observational Study.

Background: Although minor (mild-to-moderate) trauma generally leads to favorable outcomes, some patients experience in-hospital mortality. Traditional trauma severity scores alone may not sufficiently reflect the prognostic variability in aging populations with comorbidities. This study examined the associations between patient characteristics and in-hospital mortality among patients with minor trauma. Methods: This retrospective cohort study used data from adult patients with minor trauma, defined by an Injury Severity Score (ISS) < 16 from the Japan Trauma Data Bank. A logistic regression analysis was performed to evaluate associations between mortality and patient characteristics, including age, sex, ISS, and the Charlson Comorbidity Index (CCI) score. Subgroup analyses were conducted among patients with moderate trauma (ISS 9-15) to examine the associations between the Abbreviated Injury Scale (AIS) scores of injuries at three specific anatomical regions and in-hospital mortality. Results: After applying the exclusion criteria, of the 56,821 patients with ISS < 16 identified in the Japan Trauma Data Bank, 50,087 were included in the final analysis. The logistic regression analysis identified older age, male sex, ISS ≥ 9, and higher CCI scores as independent predictors of in-hospital mortality. In patients with moderate trauma, the AIS scores of injuries involving the three regions (head/neck, abdomen, and external/other trauma injury regions) were significantly associated with increased mortality. Conclusion: Among patients with minor trauma, advanced age, male sex, comorbidities, and specific injury regions were associated with increased in-hospital mortality. These findings highlight the importance of early risk recognition and tailored clinical management in this population.