Restless legs syndrome in patients on hemodialysis: Polysomnography findings

Introduction Restless legs syndrome (RLS) is a highly prevalent sleep movement disorder usually accompanied by periodic limb movements of sleep (PLMS). The incidence of RLS and PLMS in patients with end-stage renal disease (ESRD) on dialysis is much higher. Clinically, RLS and PLMS can co-occur. We hypothesized that patients with ESRD on dialysis would have a distinct presentation of RLS, with a higher prevalence of PLMS. Methods We examined clinical, demographic, biochemical, and polysomnographic characteristics of RLS in patients on dialysis matched to control subjects with normal renal function based on age, sex, body mass index, and frequency of apneas and hypopneas per hour of sleep, defined by the apnea and hypopnea index (AHI), in a proportion of 3:1. Patients with ESRD were on hemodialysis three times per week. Polysomnography was performed overnight in the sleep laboratory. Findings Patients on dialysis compared to control subjects had a lower amount of N3 sleep (77.6 ± 39.9 minutes vs. 94.8 ± 33.7 minutes, p = 0.037) and REM sleep (55.6 ± 27.5 minutes vs. 74.1 ± 28.4 minutes, p = 0.006), regardless of the presence of RLS. Among the patients on dialysis, those with RLS had higher PLMS. In the control group, patients with RLS had a lower ferritin level, which was not observed in the dialysis group. There was a significant interaction between PLMS and ESRD (p = 0.001), with a higher prevalence of PLMS in patients with ESRD on dialysis in a model adjusted for AHI, sex, arousals, and age. Factors that were associated with PLMS were RLS (p = 0.003), ESRD (p = 0.0001), and AHI (p = 0.041), with an adjusted R2 of 0.321. Conclusion RLS in patients with ESRD on dialysis is independently associated with PLMS, regardless of the severity of sleep apnea, arousals, and age.