Association between predialysis hypermagnesaemia and morbidity of uraemic restless legs syndrome in maintenance haemodialysis patients: a retrospective observational study in Zhejiang, China

OBJECTIVE: The aim of the present study was to determine whether the predialysis serum magnesium level was associated with morbidity of uraemic restless legs syndrome (RLS) in maintenance haemodialysis patients. DESIGN: A retrospective observational study of morbidity of uraemic RLS was conducted. SETTING: Patients on maintenance haemodialysis three times a week. PARTICIPANTS: We reviewed 578 patients receiving maintenance haemodialysis for >1 year as our cohort. OUTCOME MEASURES: Uraemic RLS was diagnosed according to International RLS Study Group criteria, and hypermagnesaemia was defined as serum magnesium level >1.02 mmol/L. RESULTS: The prevalence of uraemic RLS was 14.4% in our study cohort. Univariate analysis indicated that patients with uraemic RLS differed significantly from non-RLS ones in certain demographic and clinical characteristics, including younger age, longer dialysis duration, higher serum parathyroid hormone level and higher prevalence of predialysis hyperphosphataemia and hypermagnesaemia. Binary logistic-regression model analysis indicated that predialysis hypermagnesaemia was independently associated with uraemic RLS and conferred an increase in morbidity of the syndrome (OR=2.024; 95% CI 1.160 to 3.532; p=0.013). Moreover, we found that dialysis duration and predialysis hyperphosphataemia were independently associated with morbidity of uraemic RLS. CONCLUSIONS: Our data indicated that the predialysis serum magnesium level was associated with morbidity of uraemic RLS in maintenance haemodialysis patients and that predialysis hypermagnesaemia might serve as an independent risk factor for the syndrome.