Serum magnesium levels predict mortality in veterans with HF

Ambulatory serum levels of magnesium demonstrate an independent U-shaped association with mortality at 1 year among US veterans with heart failure (HF), reveals a study. The risk is lowest between 1.6 and 2.6 mg/dL and is increased at both lower higher and lower levels.

“Most clinical laboratories define normal serum magnesium as 1.6‒2.6 mg/dL, but this range may include chronic latent magnesium deficiency,” the investigators said. “The Magnesium Global Network (MaGNet) recommends 2.1‒2.3 mg/dL as optimal.”

The investigators used ambulatory serum magnesium levels to categorize 627,349 veterans with HF (2001‒2023) in the following: <1.6 (6 percent), 1.6‒1.7 (11 percent), 1.8‒2.0 (39 percent), 2.1‒2.3 (34 percent; reference), and >2.3 (10 percent) mg/dL. They estimated multivariable-adjusted hazard ratios (HRs) and 95 percent confidence intervals (CIs) for 1-year mortality using Cox models.

Finally, nonlinear associations between serum magnesium as a continuous variable were assessed via restricted cubic spline models, using two reference values: the lower limits of the current clinical reference range (1.6‒2.6 mg/dL) and the MaGNet range (2.1‒2.3 mg/dL).

Of the patients, 15.4 percent with serum magnesium <1.6 (HR, 1.36, 95 percent CI, 1.32‒1.41), 13.3 percent with 1.6‒1.7 (HR, 1.23, 95 percent CI, 1.20‒1.26), 11.6 percent with 1.8‒2.0 (HR, 1.07, 95 percent CI, 1.05‒1.09), 11.5 percent with 2.1‒2.3 (HR, 1.00; reference), and 16.2 percent with >2.3 mg/dL (HR, 1.23, 95 percent CI, 1.20‒1.26) died of any cause.

When using 1.6‒2.6 mg/dL as the reference, restricted cubic spline analysis revealed a U-shaped association, with the lowest risk between 1.6 and 2.6 mg/dL and significantly increased risks outside of these ranges.

“Magnesium is essential for myocardial function and rhythm,” the investigators said. “Although typically well-regulated, patients with HF are prone to magnesium deficiency.”