Evaluating the complex association between Social Vulnerability Index and trauma mortality

Abstract

Introduction: Social determinants of health are known to impact patient-level outcomes, but they are often difficult to measure. The Social Vulnerability Index was created by the Centers for Disease Control to identify vulnerable communities using population-based measures. However, the relationship between SVI and trauma outcomes is poorly understood.

Methods: In this retrospective study, we merged SVI data with a statewide trauma registry and used three analytic models to evaluate the association between SVI quartile and inpatient trauma mortality: (1) an unadjusted model, (2) a claims-based model using only covariates available to claims datasets, and (3) a registry-based model incorporating robust clinical variables collected in accordance with the National Trauma Data Standard.

Results: We identified 83,607 adult trauma admissions from January 1, 2017, to September 30, 2020. Higher SVI was associated with worse mortality in the unadjusted model (odds ratio, 1.72 [95% confidence interval, 1.30-2.29] for highest vs. lowest SVI quintile). A weaker association between SVI and mortality was identified after adjusting for covariates common to claims data. Finally, there was no significant association between SVI and inpatient mortality after adjusting for covariates common to robust trauma registries (adjusted odds ratio, 1.10 [95% confidence interval, 0.80-1.53] for highest vs. lowest SVI quintile). Higher SVI was also associated with a higher likelihood of presenting with penetrating injuries, a shock index of >0.9, any Abbreviated Injury Scale score of >5, or in need of a blood transfusion (p < 0.05 for all).

Conclusion: Patients living in communities with greater social vulnerability are more likely to die after trauma admission. However, after risk adjustment with robust clinical covariates, this association was no longer significant. Our findings suggest that the inequitable burden of trauma mortality is not driven by variation in quality of treatment, but rather in the lethality of injuries. As such, improving trauma survival among high-risk communities will require interventions and policies that target social and structural inequities upstream of trauma center admission.

Level of evidence: Prognostic / Epidemiologic, Level IV.