A Retrospective Multimodal Analysis of Sleep in Children With Tourette Syndrome: Integrating Clinical History, Blood Biomarkers (Vitamin D and Ferritin Levels), Actigraphy, Video Polysomnography, and Subjective Tic Assessments

Gilles de la Tourette Syndrome (TS) is a neurobehavioural condition characterised by persistent motor and vocal tics, with symptom onset typically around the age of six. Tics are described as sudden, rapid, and repetitive involuntary movements. While the core clinical features of TS are well established, the effects of TS on sleep in children remain poorly understood.

Difficulties with sleep are frequently reported in children, including trouble initiating sleep, frequent night-time awakenings, decreased sleep efficiency, excessive sleep duration, and parasomnias such as night terrors and sleepwalking. Increasing evidence suggests that sleep problems are highly common among children with TS, with reported rates of sleep disorders ranging widely from 9% to 80%. The most frequent sleep disorders reported in this population include insomnia, excessive daytime sleepiness, and disorders of arousal. Beyond the diagnosis of specific sleep disorders, studies have shown that children with TS most commonly exhibit prolonged sleep onset and reduced total sleep efficiency compared to typically developing peers. Considering sleep plays a critical role in daytime functioning and is predictive of neurodevelopment, cognitive performance, and emotional wellbeing, understanding sleep problems in children with TS is of vital importance.

Previous studies of sleep problems in children with TS have primarily used a single objective sleep study. The primary method of sleep assessment is polysomnography (PSG), a sleep study that measures brain activity, heart activity, eye movements, muscle tone, limb movements, and respiratory patterns. One study using PSG found that children with TS had reduced sleep efficiency and increased arousals compared to healthy controls. Similarly, another study that utilised a different sleep study named actigraphy, a watch that tracks movement and light exposure to estimate sleep and wake, also found low sleep efficiency and a higher fragmentation index in children with TS. However, the heightened arousals observed in these studies were scored according to standard criteria for all sleep study analyses. Thus, these arousals cannot be directly attributed to tics, as they represent a general measure of wakefulness during sleep. Moreover, actigraphy has demonstrated low specificity for detecting wakefulness during sleep, although it provides a long-term and naturalistic representation of an individual's sleep. This contrasts with PSG, which may be influenced by the "first night effect", where sleep is altered by the unfamiliar sleep lab environment. Therefore, integrating findings from both PSG and actigraphy will provide a more thorough assessment of sleep in this population.

Furthermore, these objective methods of assessing sleep do not capture how the child or their parents perceive sleep quality and its effect on everyday life. Parent-report studies in TS show high rates of reported sleep disturbance and demonstrate that greater tic severity predicts increased sleep problems and worsening daytime functioning. Moreover, research comparing the concordance of objective and subjective measures of sleep has shown a discrepancy. Subjective reports of sleep in children with TS have consistently underestimated night-time awakenings and overestimated total sleep time compared with actigraphy and PSG results. This discrepancy highlights that subjective measures capture perceptual and experiential aspects of sleep that are not captured in physiological recordings, underscoring the value of including targeted subjective measures when investigating sleep problems in TS.

Previous research investigating sleep problems in children with TS has not examined arousals attributable to tics, has relied on a single objective method to assess sleep patterns, and has not combined objective and subjective measures of sleep to provide a comprehensive characterisation of sleep in this population. This highlights a gap in the research with respect to combining objective data from PSG and actigraphy with subjective reports. To address this, the present study will apply novel Tic indices during PSG analysis of children with TS to quantify tic-related sleep disruption, alongside a newly developed Tic in Sleep questionnaire to provide a holistic evaluation of how TS affects sleep and daytime functioning. The investigators will test the hypothesis that children with TS will exhibit poorer sleep quality, both objectively and subjectively, compared to historical control data from healthy children.