Heart rate variability during sleep in children and adolescents with restless sleep disorder: a comparison with restless legs syndrome and normal controls

Abstract

Study Objectives: Restless sleep disorder (RSD) has recently been characterized clinically and polysomnographically in children and differentiated from restless legs syndrome (RLS). Heart rate variability is a reliable method to quantify autonomic changes during sleep. The aim of this study was to characterize heart rate variability in children with RSD, RLS, and individuals without these disorders, with the hypothesis that children with RSD have a shift toward sympathetic predominance during sleep. Methods: We analyzed polysomnographic recordings from 32 children who fulfilled RSD diagnostic criteria (19 boys and 13 girls), 32 children with RLS (20 boys and 12 girls), and 33 individuals without disorders (17 boys and 16 girls). Four electrocardiographic epochs were chosen, 1 for each stage, and were analyzed for automatic detection of R waves. Time domain and frequency domain heart rate variability parameters were obtained and analyzed. Results: In terms of time domain, only the standard deviation of the average interval between successive R waves during stage N3 was slightly but significantly higher in patients with RSD than in patients with RLS. In terms of frequency domain, in patients with RSD, the very-low-frequency and low-frequency bands were increased (vs patients with RLS and individuals without disorders, respectively), whereas low-frequency/high-frequency ratio tended to be increased in both patients with RSD and with RLS. In rapid eye movement sleep, low-frequency/high-frequency ratio was increased in both patients with RSD and with RLS. The low-frequency/high-frequency ratio increased in patients with RLS during quiet wakefulness preceding sleep. Conclusions: Children with RSD have increased sympathetic activation during sleep, particularly N3 and rapid eye movement sleep, compared with individuals without disorders but, as expected, not during wakefulness. Differently, children with RLS have sympathetic activation during relaxed wakefulness preceding sleep and during sleep.

Assessment of Executive and Cognitive Functions in Children with Restless Sleep Disorder: A Pilot Study

“…In this respect, it is important to emphasize that sleep microstructure has been reported to be correlated with cognitive processing and next-day cognitive performance [ 47 , 48 , 49 ]; thus, it might also have a role in cognitive changes in RSD. The microstructural sleep impairment in children with RSD is further supported by an increased sympathetic activation during sleep, which was found during N3 and REM sleep in particular through analyzing heart rate variability [ 16 ].…”

“…RSD is found in 7.7% of children referred to sleep centers, a prevalence around that of insomnia (7.3%), and below the prevalence of restless legs syndrome (10.3%) [ 14 ]. The pathophysiology of RSD has not been completely elucidated, but some postulated theories include sleep instability, sympathetic activation, and iron deficiency [ 12 , 15 , 16 ]. Treatment with oral or intravenous iron has been shown to improve the symptoms of RSD [ 17 ].…”

Sleep Disorders in Childhood

“… 83 The estimated prevalence of restless sleep disorder in a clinical sleep setting is 7.7% 84 . The pathophysiology of restless sleep disorder is unknown, but there are at least three possible causes: iron deficiency, sleep instability, and sympathetic activation 85–87 . Iron supplementation (oral and IV) improves symptoms (per parent report) in patients with restless sleep disorder 85 …”

Restless sleep disorder, restless legs syndrome, and periodic limb movement disorder—Sleep in motion!

“…In normal sleep, the transition from wakefulness to sleep is accompanied by a switch from sympathetic to parasympathetic predominance manifested by slowing in heart rate and respiration 31 . Heart rate variability (HRV), a marker of sympathetic/parasympathetic balance, was analyzed in a group of children with RSD with the hypothesis that in these children, a shift toward sympathetic predominance is present during sleep 32 . Indeed, the hypothesis was confirmed because HRV in children with RSD showed increased sympathetic activation during sleep, particularly during stages N3 and rapid‐eye‐movement (REM) when compared with controls 32 .…”

“…Heart rate variability (HRV), a marker of sympathetic/parasympathetic balance, was analyzed in a group of children with RSD with the hypothesis that in these children, a shift toward sympathetic predominance is present during sleep 32 . Indeed, the hypothesis was confirmed because HRV in children with RSD showed increased sympathetic activation during sleep, particularly during stages N3 and rapid‐eye‐movement (REM) when compared with controls 32 . This finding, together with those reported above, point to the idea that RSD is a disorder in which sleep is disrupted in a probably subtle but complex way leading to the speculation that RSD can potentially have cardiovascular consequences.…”