Heart Rate Variability in Restless Legs Syndrome and Periodic Limb Movements of Sleep

Introduction: The relationship between the autonomic nervous system and restless legs syndrome (RLS) and periodic limb movements of sleep (PLMS) consists of varied and somewhat conflicting reports. In order to further elucidate these complexities, a retrospective analysis of polysomnography (PSG) records and clinical data was performed. Methods: Records from 233 adult subjects were randomly selected and organized into one of four groups (non-RLS/PLMS [n = 61], RLS [n = 60], PLMS [n = 58], and RLS/PLMS [n = 54]). Heart rate variability (HRV) analysis was based on 5-minute samples of 2-lead electrocardiogram data isolated from PSG recordings during wakefulness and NREM sleep, and included mean RR interval (labeled NN) and standard deviation of the RR intervals (labeled SDNN), and HRV power, very low frequency (VLF), low frequency (LF), and high frequency (HF) spectral bands. Results: A significant reduction in the VLF band in the PLMS group as compared to the non-RLS/PLMS group (542 +/- 674 vs. 969 +/- 1025 ms(2), p = 0.038) was found in wakefulness. Statistically significant differences were seen in the PLMS group as compared to the non-RLS/PLMS group with a reduction in SDNN (p = 0.001) and the HF (p = 0.001) band, and an increase in HRV power p = 0.001), and the VLF (p = 0.005) and LF (p = 0.001) bands in NREM sleep. Conclusions: The PLMS group exhibited reduced basal sympathetic activity in wakefulness, but basal sympathetic predominance during NREM sleep, distinguishing this group from the RLS and RLS/PLMS groups.