BackgroundThe stress index (SI), defined as the serum glucose to potassium ratio, has emerged as a potential prognostic indicator in some patient populations. This study aims to evaluate the predictive value of SI on the trauma patients sustained by all trauma causes. MethodsA retrospective analysis was conducted on 20,040 adult trauma patients admitted to a single trauma center from January 1, 2009, to December 31, 2022. The SI was calculated according to the serum levels of glucose (mg/dL) and potassium (mEq/L) upon patients’ arrival to emergency room. The enrolled patients were stratified into two groups based on an optimal SI cutoff value determined by receiver operating characteristic (ROC) curve analysis. The association between SI and in-hospital mortality, as well as other clinical outcomes, was assessed using multivariate logistic regression, adjusting for potential confounders. ResultsThe mortality patients had a significantly higher SI (59.7±30.6 vs. 39.5±17.5, p < 0.001) than those who survived. The SI was identified as a significant independent predictor of mortality (odds ratio [OR] 4.65, 95% confidence interval [CI]: 2.61–8.27, p < 0.001) in the multivariate analysis. In addition, patients in the high SI group (≥42.7) demonstrated significantly worse outcomes, including higher in-hospital mortality (7.5% vs. 1.4%, p < 0.001), longer hospital stays compared to the low SI group (<42.7). ConclusionThe SI serves as a simple and valuable prognostic tool in risk stratification of the trauma patients.