Evaluating the Prognostic Significance of Magnesium Levels in Emergency Department Admissions: The Largest Retrospective Cohort Study

Background: Previous research has reported hypermagnesemia (hyperMg) in the emergency department (ED) as an independent mortality factor, however there are no studies which evaluated consecutive cases because magnesium (Mg) is routinely measured. On the other hand, hypomagnesaemia (hypoMg) in the ED is controversial. Our study aims to address these limitations and provide a comprehensive analysis of the relationship between Mg levels and mortality. Methods: We conducted a retrospective cohort study of patients admitted in the ED of the Anjo Kosei Hospital, Japan. Consecutive patients more than 18 years old from January 2017 to December 2019 were included. Patients were divided into three groups according to Mg categories (Mg ≦ 1.5, 1.5 < Mg ≦ 2.4, and Mg < 2.5 mg/dL). We investigated association Mg levels and 28-day death using multivariable Cox proportional hazard model. Restricted Cubic Spline (RCS) analysis was also performed for evaluation of non-linear relationship. Results: There were 43,100 ED visits and 43,808 cases of Mg data are available. Among included 11,532 patients (mean age, 75 years; 58% male; mean Mg, 2.1 mg/dL; mean length of hospital stay, 11days), 404 (3.6%), 9,826 (85.2%), and 1,302 (11.2%) patients were classified as hypoMg, normoMg, and hyperMg, respectively. Survival curves are shown in Figure A. RCS analysis in Figure B showed no significant increase in the hazard ratio for hypomagnesemia, but a significantly higher hazard ratio for hypermagnesemia in multivariate-adjusted models after adjustment for CRP and Alb. Conclusion: In patients admitted from the ED, HyperMg was associated with 28-day mortality, while hypoMg was not associated.