Low Magnesium Linked to Worse Survival in Hemodialysis Patients

Two studies confirm the association, but it remains unclear whether correcting hypomagnesemia will lessen the likelihood of adverse outcomes.
Two studies confirm the association, but it remains unclear whether correcting hypomagnesemia will lessen the likelihood of adverse outcomes.

Two new studies implicate low serum magnesium levels with worse survival among hemodialysis (HD) patients.

A study led by Kamyar Kalantar-Zadeh, MD, MPH, PhD, of the University of California Irvine, found that, after adjusting for demographics and comorbid conditions, HD patients with a serum magnesium level below 1.8 mg/dL had a significant 39% increased risk of mortality compared with those who had a reference level of at least 2.2 but less than 2.4 mg/dL. 

The other study, led by Eduardo Lacson Jr. MD, MPH, formerly of Fresenius Medical Care North America, Waltham, Mass., found that HD patients with serum magnesium levels below 1.30 mEq/L had a significant 63% increased risk of death compared with patients who had a serum magnesium reference value of at least 1.60 but less than 1.90 mEq/L in unadjusted analyses. The increased risk was attenuated, but still significant, after adjusting for case-mix and laboratory variables.

The findings of both studies were published online ahead of print in the American Journal of Kidney Diseases.

The study by Dr. Kalantar-Zadeh and his colleagues included 9,359 maintenance HD patients treated at DaVita facilities. Of these, 2,636 died over 5 years. Among other findings, the investigators observed “a differential association between serum magnesium level and mortality across serum albumin levels such that hypomagnesemia had a particularly stronger association with death among patients with low albumin levels.”

Dr. Kalantar-Zadeh's team concluded: “Interventional studies are warranted to examine whether correction of hypomagnesemia ameliorates adverse outcomes in this population.”

Dr. Lacson's group conducted an initial exploratory study of 21,534 HD patients and a 1-year follow-up study of 27,544 HD patients. In the follow-up study, during which 4,531 patients died, the investigators observed a linear decline in death risk from the lowest to the highest serum magnesium category, with the best survival at serum magnesium levels of 2.50 mEq/L or higher. Patients in this category had a significant 32% decreased death risk compared with the reference value in unadjusted analyses.

Additionally, Dr. Lacson and his colleagues found that the association between high serum magnesium and lower mortality risk was consistent in subgroups of diabetic and non-diabetic patients, although the association became non-significant in adjusted analyses. High serum magnesium was associated with better survival with respect to cardiovascular and non-cardiovascular deaths, but the association also lost significance in adjusted analyses, with the caveat of smaller sample sizes within these subgroup analyses.

The researchers pointed out that “serum magnesium level is only one of many factors that may influence risk of death. Thus, although it is prudent for physicians to evaluate for treatable causes of hypomagnesemia only adequately powered long-term prospective interventional studies will be able to determine whether therapeutic adjustment of serum magnesium levels can be beneficial for HD patients.”

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