Abstract
Sleep-related Rhythmic Movement Disorder (RMD) affects around 1% of UK pre-school children. Little is known about RMD in Down syndrome (DS). We aimed to determine: (a) the prevalence of RMD in children with DS aged 1.5–8 years; (b) phenotypic and sleep quality differences between children with DS and RMD and sex- and age-matched DS controls; and (c) night-to-night variability in rhythmic movements (RMs). Parents who previously reported RMs from a DS research registry of 202 children were contacted. If clinical history suggested RMD, home videosomnography (3 nights) was used to confirm RMs and actigraphy (5 nights) was used to assess sleep quality. Phenotype was explored by demographic, strengths and difficulties, Q-CHAT-10/social communication and life events questionnaires. Eight children had confirmed RMD. Minimal and estimated maximal prevalence were 4.10% and 15.38%, respectively. Sleep efficiency was significantly lower in RMD-cases (69.1%) versus controls (85.2%), but there were no other phenotypic differences. There was considerable intra-individual night-to-night variability in RMs. In conclusion, RMD has a high prevalence in children with DS, varies from night to night and is associated with poor sleep quality but, in this small sample, no daytime phenotypic differences were found compared to controls. Children with DS should be screened for RMD, which is amenable to treatment.
Highlights
Sleep-related rhythmic movement disorder (RMD) is a rare sleep disorder [1] with a likely prevalence of around 1% in UK pre-school children established by our recent community-based study of 1464 infants and toddlers [2]
Using stringent objective diagnostic criteria, RMD is significantly more common in children with Down syndrome (DS) than it is in a general population of infants and toddlers [2]
RMD is associated with significantly worse sleep quality
Summary
Sleep-related rhythmic movement disorder (RMD) is a rare sleep disorder [1] with a likely prevalence of around 1% in UK pre-school children established by our recent community-based study of 1464 infants and toddlers [2]. Rhythmic movements (RMs) include body rocking, head banging or head rolling [4]. RMD is hypothesised to be a conditioned, self-soothing behaviour that mimics maternal movements, heartbeat or respiratory rhythm experienced in utero [3]. Rocking in general (including non-sleep-related) may be a soothing behaviour in response to current life events; patterns of rocking were found in 47% of 144 institutionally reared Romanian children, aged between a few weeks and 43 months at the time of UK entry for adoption; this decreased to 18% by age 6 years [5]. The cause of RMD, and its impact on sleep and daytime function, is poorly understood [3]
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