The synergy of nutritional risk and iron deficiency as a predictor of mortality in older emergency department patients.

Background: Older patients in the emergency department (ED) often present with coexisting nutritional risk and iron deficiency (ID). However, this combined risk is frequently underrecognized and inadequately addressed in clinical practice. Objective: To investigate the independent and combined predictive value of nutritional risk and ID for 28-day mortality in older ED patients, and to clarify the underlying pathway-specifically, examining whether hemoglobin (Hb) acts as a mediator or whether direct effects are present. Methods: This prospective cohort study enrolled 443 patients aged ≥ 60 years from the ED resuscitation room. Patients were stratified into four groups based on their modified Nutrition Risk in the Critically Ill (mNUTRIC) score and ID status: G1, mNUTRIC < 5 without ID; G2, mNUTRIC < 5 with ID; G3, mNUTRIC ≥ 5 without ID; G4, mNUTRIC ≥ 5 with ID. Multivariate Cox regression was used to identify independent risk factors for mortality. Mediation analysis was performed to explore potential mechanistic pathways. Results: The overall 28-day mortality rate was 22.8%. Patients with both high nutritional risk and ID (G4) had the highest mortality (42.7%) and a risk 4.9 times greater than the G1 (adjusted HR = 4.901, 95% CI: 2.861-8.394, Conclusion: The coexistence of high nutritional risk and ID exerts a powerful synergistic effect on mortality in older ED patients. Although associated with hemoglobin levels, this synergy appears to be primarily direct, suggesting that mechanisms beyond anemia contribute to the excess mortality. Integrated assessment of this "risk triad" may help identify high-risk patients earlier.