Night Sleep Architecture and Rhythmic Movement Disorder

Rhythmic movement disorder (RMD), a rare sleep-related motor disorder, is associated with disturbed nighttime sleep and sleep continuity in children and adults, according to study results published in Sleep.

Patients with RMD exhibit severe rhythmic movements may develop significant functional impairment and are at an increased risk for injuries. As there are limited data regarding sleep architecture in these patients, the goal of the current case-control study was to assess the clinical and polysomnographic characteristics of patients with RMD.

The study cohort comprised of 50 participants with a known diagnosis of RMD, including 27 children ≤16 years and 23 patients >16 years old.

In addition, 75 sex-matched controls (42 children ≤16 years) without repetitive movements or other sleep disorders were recruited from the general population.

Most participants in the study cohort (82%) reported disturbed nighttime sleep, altered daytime functioning (80%), and family member’s sleep disruption (72%). Almost half of patients (46%) had a known neurodevelopmental disorder, the most commons were specific learning disorders (30%), and attention-deficit and hyperactivity disorder (26%). Affective and sleep disorders  were also common in this group.

Polysomnography data revealed that while no rhythmic movements were evident in the controls, 82% of patients with RMD had ≥1 rhythmic movements and 78% had >10 sequences.

Most of the rhythmic movements emerged from wakefulness (67.8% of sequences) and the majority were observed after sleep onset. The rolling subtype of rhythmic movement was the most frequent one (76.2%), followed by a rocking/banging subtype (23.8%).

Nighttime disturbed sleep was common in patients with RMD, as the total sleep time and sleep efficiency were reduced in adults with the disorder, compared with controls, while sleep latency, wake after sleep onset duration and microarousal index were increased. In children, sleep efficiency was reduced and wake after sleep onset duration was increased in those with RMD, compared with controls.

There was an independent association between the severity of rhythmic movements and sleep disruption, including reduced sleep efficiency, increased wake after sleep onset duration, longer sleep onset, and increased microarousal index.

The researchers acknowledged several limitations of the study, including the retrospective design, small sample size, potential bias towards selecting more severe cases as the participants were treated at a tertiary sleep clinic, lack of standardized psychometric tools to assess disturbed daytime functioning, and inability to exclude potential impact of other comorbidities on the association between RMD and disturbed nighttime sleep.

“Rhythmic movement disorder is a rare, highly comorbid and disabling condition both in children and adults with frequent disturbed nighttime sleep that may contribute to the burden of the disease,” concluded the researchers.

Reference

Laganière C, Pennestri MH, Rassu AL, et al. Disturbed nighttime sleep in children and adults with rhythmic movement disorder [published online May 27, 2020]. Sleep. doi:10.1093/sleep/zsaa105