Neutrophil-to-lymphocyte ratio as a predictor of in-hospital mortality in elderly emergency patients: a retrospective study from Southern Iran

Mortality risk stratification in older emergency department (ED) patients remains challenging in resource-limited settings, particularly among frail elderly with multiple comorbidities. This study evaluated the prognostic value of the neutrophil-to-lymphocyte ratio (NLR) in Southern Iran. In this retrospective single-center study conducted between March 2021 and March 2022, we analyzed records of 2,540 consecutively admitted patients aged ≥ 65 years to an academic ED in Southern Iran. NLR was calculated from initial complete blood counts. An NLR > 3.75 predicted in-hospital mortality with 52.2% sensitivity and 75.8% specificity (AUC = 0.655; 95% CI: 0.636–0.674; p < 0.001). Multivariate analysis confirmed NLR as an independent predictor (adjusted OR = 1.77; 95% CI: 1.28–2.44). An inverse association was observed between hypernatremia and mortality risk (OR = 0.68; 95% CI: 0.57–0.82). NLR > 3.75 may serve as a supportive and low-cost indicator for mortality risk stratification in elderly emergency patients; however, it should not be considered a stand-alone triage tool. The unexpected inverse association with hypernatremia warrants cautious interpretation and validation in future studies.