Sleep in children with Smith-Magenis syndrome; a case-control actigraphy study.

Study Objectives: The objectives of the study were (1) to compare both actigraphy and questionnaire-assessed sleep quality and timing in children with Smith-Magenis syndrome (SMS) to a chronologically age-matched typically developing (TD) group and (2) to explore associations between age, nocturnal and diurnal sleep quality, and daytime behavior. Methods: Seven nights of actigraphy data were collected from 20 children with SMS (mean age 8.70; SD 2.70) and 20 TD children. Daily parent/teacher ratings of behavior and sleepiness were obtained. Mixed linear modeling was used to explore associations between total sleep time and daytime naps and behavior. Results: Sleep in children with SMS was characterized by shorter total sleep time (TST), extended night waking, shorter sleep onset, more daytime naps, and earlier morning waking compared to the TD group. Considerable inter-daily and inter-individual variability in sleep quality was found in the SMS group, so caution in generalizing results is required. An expected inverse association between age and TST was found in the TD group, but no significant association was found for the SMS group. No between-group differences in sleep hygiene practices were identified. A bidirectional negative association between TST and nap duration was found for the SMS group. In the SMS group, increased afternoon sleepiness was associated with increased irritability (p = .007) and overactivity (p = .005). Conclusion: These findings evidence poor sleep quality in SMS and the need to implement evidence-based interventions in this population. Statement of Significance Smith-Magenis syndrome (SMS) is characterized by circadian rhythm abnormalities, however, research investigating the impact of circadian rhythm disturbance on children's sleep is limited. Children with SMS experience both daytime sleepiness and behavioral difficulties, but their relationship has not been studied. We described actigraphy data which contrasts sleep of children with SMS to that of agematched typically developing children. Using temporal analysis, we identified a relationship between behavioral difficulties and daytime sleepiness and a hypothesized homeostatic relationship between nocturnal and diurnal sleep in SMS. Implications for intervention include individualized assessment of sleep for children with SMS given variation in sleep quality between children and a combination of behavioral (e.g. nap restriction) and pharmacological approaches to improve sleep quality.