Hospital level does not influence 30-day in-hospital mortality in road traffic accident hospitalisations - a nationwide registry study utilising Explainable AI (XAI) and the ICD-10 based injury severity score (ICISS)

Background: Globally, road traffic accidents (RTAs) remain a leading cause of mortality, particularly among individuals aged 15–30 years. Sweden has been at the forefront of traffic safety, but in-hospital care is critical in determining outcomes following RTAs. Guided by North American data demonstrating improved survival rates at trauma centres, the Swedish healthcare system is shifting towards trauma centralisation. However, comprehensive national data specific to Sweden remain underexplored. The unique demographic characteristics of Sweden, including vast, sparsely populated regions, distinguish it from other Western nations, complicating direct comparisons. Methods: The epidemiology and risk factors for 30-day mortality from RTAs in Sweden were investigated for 95,954 hospital admissions from 2008 to 2021. The ICD-based injury severity score (ICISS), age, sex, the Charlson comorbidity index (CCI), the year of the event, and hospital level were examined using an explainable AI (XAI) and Logistic regression. Results: The most important factors for 30-day mortality were, in decreasing importance, ICISS, age, CCI, event year, hospital level, and sex. There was a clear trend towards centralising RTA care, with Level 1 hospitals catering to the most critically injured patients. In parallel, however, the hospital level did not affect risk-adjusted traffic-related mortality. XAI enhances mortality prediction over logistic regression, confirming these findings. Discussion: This study presents the most extensive analysis of in-hospital outcomes for road traffic accidents (RTAs) in Europe to date. Factors such as ICISS, age, sex and the CCI had anticipated effects on outcome. Overall treatment outcome, measured as mortality improved over time. Conclusion: The presumption that external validity for trauma centralisation is applicable in the Scandinavian trauma context is not convincing. These findings make it essential to investigate further the trauma organisation given Scandinavian prerequisites so that time to hospital is not sacrificed for the type of hospital.