Association of serum magnesium with all-cause mortality in patients with and without chronic kidney disease in the Dallas Heart Study

Background. Low serum magnesium (SMg) has been linked to increased mortality and cardiovascular disease (CVD) in the general population. We examined whether this association is similar in participants with versus without prevalent chronic kidney disease (CKD) in the multiethnic Dallas Heart Study (DHS) cohort. Methods. SMg was analyzed as a continuous variable and divided into tertiles. Study outcomes were all-cause death, cardiovascular (CV) death or event, and CVD surrogate markers, evaluated using multivariable Cox regression models adjusted for demographics, comorbidity, anthropometric and biochemical parameters including albumin, phosphorus and parathyroid hormone, and diuretic use. Median follow-up was 12.3 years (11.9-12.8, 25th percentile-75th percentile). Results. Among 3551 participants, 306 (8.6%) had prevalent CKD. Mean SMg was 2.08 +/- 0.19mg/dL (0.85 +/- 0.08mM, mean +/- SD) in the CKD and 2.07 +/- 0.18mg/dL (0.85 +/- 0.07mM) in the non-CKD subgroups. During the follow-up period, 329 all-cause deaths and 306 CV deaths or events occurred. In a fully adjusted model, every 0.2mg/dL decrease in SMg was associated with similar to 20-40% increased hazard for all-cause death in both CKD and non-CKD subgroups. In CKD participants, the lowest SMg tertile was also independently associated with all-cause death (adjusted hazard ratio 2.31; 95% confidence interval 1.23-4.36 versus 1.15; 0.55-2.41; for low versus high tertile, respectively). Conclusions. Low SMg levels (1.4-1.9mg/dL; 0.58-0.78 mM) were independently associated with all-cause death in patients with prevalent CKD in the DHS cohort. Randomized clinical trials are important to determine whether Mg supplementation affects survival in CKD patients.