Risk factors for restless legs syndrome in dialysis patients

Restless legs syndrome (RLS) is a movement disorder that affects 6.6-62% of dialysis patients. The aims of this multicentre cross-sectional study were to document the frequency, prevalence and severity of RLS in patients attending 5 dialysis centres for chronic hospital haemodialysis (HHD) and to identify associated risk factors.

The diagnosis of RLS was made using the criteria of The International Restless Legs Study Group. The following data were collected: age; gender; duration of renal replacement therapy (RRT); current smoking status; urea reduction ratio; weekly erythropoietin dose; weekly intravenous iron dose; prescribed beta blocker; prescribed renin/angiotensin system inhibitors and pre-dialysis blood concentrations of haemoglobin, ferritin, total calcium (corrected for albumin), albumin, phosphate, parathyroid hormone. Associations with RLS were analysed by univariate and multivariate logistic regression.

Data relating to 277 of 295 patients who had been attending for regular HHD for > 3 months were collected. RLS was present in 127 (45.8%). 82 (29.6%), 27 (9.7%) and 18 (6.5%) patients had mild, moderate and severe RLS, respectively. 39 patients (14.1%) were prescribed medicines aimed at reducing RLS. 30 (76.9%) of these 39 patients still had RLS. Female gender (RR 2.17; p = 0.01), increasing duration since first dialysis (RR 1.06 per year; p = 0.03) and increasing body weight (RR 1.02 per kg; p = 0.02) were independent risk factors for RLS by multivariate analysis. In contrast to previous studies, we found no association with iron status, haemoglobin, serum phosphate or smoking.

There is a high prevalence of RLS in our population and therapeutic intervention appears to have limited efficacy. The associations with female gender, duration of RRT and body weight deserve further study.