Serum electrolytes as prognostic markers: a new frontier in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) management

Abstract

Background: Chronic obstructive pulmonary disease (AECOPD) is the fourth leading cause of death worldwide. This study demonstrated for the first time that serum sodium and calcium imbalances are independent predictors of AECOPD prognosis and explored the relationship between serum electrolyte levels and the prognosis of patients with AECOPD. Methods: This retrospective study included 535 AECOPD patients admitted to The First Hospital of Lanzhou University between October 2021 and May 2023. Serum electrolyte levels, specifically sodium ion and calcium ion levels, were considered exposure variables, whereas AECOPD prognosis was defined as the presence or absence of readmission within 1 year. Logistic regression and Cox regression analyses were used to evaluate the associations between serum sodium and calcium levels and the risk of readmission within 1 year, supplemented by subgroup analysis, sensitivity analysis, and Kaplan-Meier survival analysis. Results: Compared with patients not readmitted within 1 year, readmitted patients had lower sodium (Na+ <139 mmol/L) and higher calcium (Ca2+ >2.20 mmol/L) levels. Multivariate logistic regression and Cox regression analyses confirmed that lower sodium and higher calcium levels were independently associated with 1-year readmission risk. Subgroup analysis demonstrated a stable independent association across multiple subgroups. Two sensitivity analyses consistently confirmed the robustness of these associations. Finally, Kaplan-Meier survival analysis revealed significant differences in the cumulative risk of readmission within 1 year among the different sodium and calcium groups. Conclusions: Serum sodium and calcium levels are independently associated with 1-year readmission risk in AECOPD patients, and early detection and management of sodium and calcium imbalances may improve clinical outcomes. To establish a causal relationship and further explore the interaction of pathophysiological mechanisms, multicenter prospective studies are warranted.