Impact of serum magnesium levels at hospital discharge and one-year mortality

Abstract

Background: We aimed to determine the optimal range of discharge serum magnesium in hospitalized patients by evaluating one-year mortality risk according to discharge serum magnesium. Methods: This was a single-center cohort study of hospitalized adult patients who survived until hospital discharge. We classified discharge serum magnesium, defined as the last serum magnesium within 48 hours of hospital discharge, into ≤1.6, 1.7–1.8, 1.9–2.0, 2.1–2.2, and ≥2.3 mg/dL. We assessed one-year mortality risk after hospital discharge based on discharge serum magnesium, using discharge magnesium of 2.1–2.2 mg/dL as the reference group. Results: Of 39,193 eligible patients, 8%, 23%, 34%, 23%, and 12% had a serum magnesium of ≤1.6, 1.7–1.8, 1.9–2.0, 2.1–2.2, and ≥2.3 mg/dL, respectively, at hospital discharge. After the adjustment for several confounders, discharge serum magnesium of ≤1.6, 1.7–1.8, and ≥2.3 mg/dL were associated with higher one-year mortality with hazard ratio of 1.35 (95% CI 1.21–1.50), 1.14 (95% CI 1.06–1.24), and 1.17 (95% CI 1.07–1.28), respectively, compared to discharge serum magnesium of 2.1–2.2 mg/dL. There was no significant difference in one-year mortality between patients with discharge serum magnesium of 1.9–2.0 and 2.1–2.2 mg/dL. Conclusion: The optimal range of serum magnesium at discharge was 1.9–2.2 mg/dL. Both hypomagnesemia and hypermagnesemia at discharge were associated with higher one-year mortality.