Impact of admission serum magnesium levels on long-term mortality in hospitalized patients

ABSTRACT

Background

The impact of admission serum magnesium on long-term mortality in hospitalized patients was unclear. This study aimed to assess the long-term mortality risk based on admission of serum magnesium in hospitalized patients.

Methods

This was a retrospective cohort study conducted at a tertiary referral hospital. We included all adult patients admitted to Mayo Clinic Hospital, Minnesota, between 1 January 2009 and 31 December 2013, who had available admission serum magnesium. We categorized serum magnesium into ≤1.4, 1.5–1.6, 1.7–1.8, 1.9–2.0, 2.1–2.2, ≥2.3 mg/dL. We estimated the 1-year mortality risk based on various admission serum magnesium levels using Kaplan-Meier plot and assessed the association of admission serum magnesium with 1-year mortality using Cox proportional hazard analysis. We selected serum magnesium of 1.7–1.8 mg/dL as the reference group for mortality comparison.

Results

We included a total of 65,974 patients, with a mean admission serum magnesium of 1.9 ± 0.3 mg/dL in this study. The 1-year mortality was 15.7%, 15.8%, 15.5%, 16.7%, 19.0%, and 25.6% in admission serum magnesium of ≤1.4, 1.5–1.6, 1.7–1.8, 1.9–2.0, 2.1–2.2, ≥2.3 mg/dL, respectively (p < 0.001). After adjustment for confounders, admission serum magnesium of 1.9–2.0, 2.1–2.2, and ≥2.3 mg/dL were significantly associated with increased 1-year mortality compared with magnesium of 1.7–1.8 mg/dL with adjusted HR of 1.09 (95% CI 1.02–1.15), 1.22 (95% CI 1.14–1.30), and 1.55 (95% CI 1.45–1.55), respectively. There was no significant difference in 1-year mortality risk between low serum magnesium ≤1.6 mg/dL and magnesium of 1.7–1.8 mg/dL.

Conclusion

Hypermagnesemia, but not hypomagnesemia, at the time of hospital admission was associated with increased 1-year mortality among hospitalized patients.

KEYWORDS:

• Magnesium
• electrolytes
• hypomagnesemia
• hypermagnesemia
• mortality

Authors’ contributions

All authors had access to the data and a role in writing the manuscript.

Declaration of interest

The authors have no commercial associations that might be a conflict of interest in regard to this article. No funding support for this article.

The contents of the paper and the opinions expressed within are those of the authors, and it was the decision of the authors to submit the manuscript for publication.

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.