Contribution of dysregulated serum magnesium to mortality in hemodialysis patients with secondary hyperparathyroidism: a 3-year cohort study

BACKGROUND: The extent of contribution of disturbed magnesium balance to mortality remains unclear among hemodialysis patients. METHODS: This was a cohort study involving 3276 patients on maintenance hemodialysis at 86 facilities in Japan from 2008 to 2010 who had secondary hyperparathyroidism (SHPT). Baseline serum magnesium (sMg) values were categorized into quintiles (≤2.3, >2.3–2.5, >2.5–2.7, >2.7–3.0 and >3.0 mg/dL), and the middle quintile was set as the reference. Outcome was all-cause death. Independent contribution to all-cause death was assessed via Cox regression to generate population-attributable fractions (PAFs). RESULTS: A total of 2165 patients from 68 facilities were analyzed. The lowest quintile of sMg was positively associated with lower serum potassium and albumin levels, higher C-reactive protein (CRP) levels and prevalence of atrial fibrillation and cerebrovascular disease than the other quintiles. The highest sMg quintile was positively associated with higher potassium levels, and negatively associated with lower serum albumin levels and higher intact parathyroid hormone and CRP levels and prevalence of cerebrovascular disease than the other quintiles. During a median follow-up of 3 years, the lowest and the second lowest quintiles of sMg were associated with all-cause death [adjusted hazard ratio (HR) 1.737, 95% confidence interval (95% CI) 1.200–2.512 and HR 1.675, 95% CI 1.254–2.238, respectively). Point estimates of adjusted HRs of the highest and the second highest sMg quintiles were higher than those of the middle quintile for all-cause death. Adjusted PAFs of lower sMg and of higher and lower sMg for all-cause death were 24.0% (95% CI 13.0–35.0%) and 30.7% (95% CI 14.5–46.8%), respectively. CONCLUSION: In hemodialysis patients with SHPT, dysregulated sMg is an important contributor to all-cause death. Further studies are warranted to examine whether or not correction of sMg improves survival.