The association between serum copper-to‑zinc ratio and mortality among older patients in the emergency department: A prospective cohort study in Taiwan

BACKGROUND: The association between the serum copper-to‑zinc (Cu/Zn) ratio and clinical outcomes in geriatric emergency department (ED) populations remains inconclusive. This study aimed to evaluate the prognostic significance of the serum Cu/Zn ratio among geriatric population in the ED setting. METHODS: We conducted a prospective observational study involving patients aged 65 years and older who were admitted to the ED observation room of a tertiary medical center in Taiwan between August 29, 2018, and November 28, 2022. The primary outcome was 3-month mortality. Participants were stratified into two groups based on the serum Cu/Zn ratio, and survival analysis using Cox proportional hazards modeling was performed with covariate adjustment. RESULTS: A total of 280 participants were included, with a mean age of 84.4 years and 62.1 % being male. The mean serum copper and zinc levels were 1130.9 μg/L and 829.9 μg/L, respectively, with a mean Cu/Zn ratio of 1.4. The 3-month mortality rate was 8.2 %. The optimal cut-off value for predicting mortality was 1.67, with an area under the curve (AUC) of 0.755. Compared to the low Cu/Zn ratio group, the high Cu/Zn ratio group had significantly higher rates of hospital admission (84.0 % vs. 56.1 %), 1-month mortality (6.7 % vs. 1.5 %), and 3-month mortality (22.7 % vs. 2.9 %). In the multivariable Cox proportional hazards model, a high Cu/Zn ratio remained independently associated with increased 3-month mortality (adjusted hazard ratio = 1.540; 95 % CI: 1.291-1.838). CONCLUSION: Among older adults in the ED, a higher serum Cu/Zn ratio was independently associated with increased 3-month mortality, highlighting its potential role as a prognostic biomarker. Further studies are warranted to investigate potential therapeutic implications.