Sleep & attention profiles in children with Autism Spectrum Disorder

Sleep serves a number of vital functions for the developing child and has been shown to have a number of critical implications for neurobehavioural functioning. A large number of school-age children do not get adequate sleep; the consequences of which can manifest in poorer behaviour and attention regulation outcomes; affecting subsequent learning and academic achievement. These associations are particularly concerning in school-age children with Autism Spectrum Disorder (ASD); with rates of sleep disturbance affecting up to 80%, and an often already compromised neurobehavioural and cognitive system. The current thesis presents a series of papers which assess the profile of sleep and attentional difficulties, as well as interrelationships between the two, in school-age (6-12 years) children with and without ASD. Children’s naturally occurring sleep-wake profiles were obtained via 14-15 days of actigraphy monitoring and complimented by the parent- completed Children’s Sleep Habits Questionnaire (CSHQ) and measures of Attention-deficit hyperactivity disorder (ADHD) behaviour. Objective assessments of children’s’ cognitive attention functioning were obtained via the Attention Network Test for Children (ANT-C) and Wilding Attention Test for Children (WATT) immediately following two weeks of actigraphic monitoring. Chapter 2 reviews existing literature around the nature of sleep and cognitive attentional functioning in children with ASD, as well as research exploring the impact children’s sleep duration and sleep quality has on their subsequent behaviour, attention and intellectual functioning. This review highlights the paucity of research studies which have examined the impact sleep difficulties may have on daytime cognitive attention and intellectual functioning in school-age children with ASD. Past ASD attentional and sleep research is additionally limited by heterogeneous ASD study groups and predominant reliance on subjective sleep measures to capture sleep. vii Chapters 3 and 4 present cross-sectional comparisons of sleep and cognitive attention profiles in school-aged children with ASD and an age-matched subgroup of the TD cohort. The results of Paper 1 (Chapter 3) serve to reinforce difficulties in the initiation of sleep, as measured by actigraphy, as a core and persistent feature of the ASD sleep profile, as well as increased severity across all aspects of the parent-reported behavioural sleep profile. In addition to these core findings, actigraphic measurement revealed more between and within- child variability in sleep onset latency (SOL) in ASD compared to TD children, which has not been documented previously, and age-related differences in children’s sleep profiles. These findings not only emphasise the importance of exploring developmental differences when investigating sleep across the school-aged years but also demonstrate the unique contribution of including multi-modal sleep assessment measures to investigate sleep in children with ASD. Analysis of children’s cognitive attention development over middle childhood via the ANT-C and WATT (Chapter 4) revealed that children with ASD exhibit deficit functioning in aspects of both the orienting and alerting attention networks, and are less responsive to visual orienting cues in early childhood, compared to TD children. In addition, analysis of both tasks together suggest that switching and sustained attention subtests from the WATT are more sensitive to the attentional problems experienced by younger and older children with ASD. The findings of this paper not only serve to highlight the importance of considering developmental trajectories when examining attentional processes but also highlight the potential utility of the ANT-C and WATT as useful tools by with which to track overt and subtle deficits and improvements in attentional functioning in children with ASD. Finally, Chapter 5 addresses gaps identified in the literature review by examination of associations between children’s objective sleep and objective/subjective attentional profiles. In both children with and without ASD, indicators of children’s sleep quality were found to viii have associations with aspects of behavioural attention; however an association between increased difficulty with sustained attention and increased sleep fragmentation was evident in TD children only. Sleep duration did not appear to have any impact on behavioural or cognitive aspects of attention for either group. Together these findings suggest that sleep interventions which are targeted at improving the quality not quantity of sleep may have greater implications for subsequent daytime functioning. Collectively, these findings address several key limitations of past research in order to more comprehensively characterise the profile of sleep and attentional problems affecting school-age children with ASD, and initiates exploration of the interrelationships between children’s naturally occurring sleep profiles and attentional functioning. The combined use of objective and subjective sleep measures served to further validate the increased frequency and severity of disturbed sleep in school-age children with ASD; suggesting that uniform screening for sleep disruption may be warranted in ASD, as well as the need for personalised, age-sensitive, and multimodal approaches to the management and treatment of sleep difficulties in this population. The early and pronounced deficits revealed in orienting attention in ASD indicate that abnormal functioning of this attention network may represent a primary disturbance of the disorder, and may, in fact, be associated with the emergence of ASD-related symptomology, and thus an appropriate target for early intervention. Together, findings support some relationship between the quality of children’s habitual sleep patterns and attentional functioning in children with and without ASD; however the increased severity and prevalence of sleep difficulties observed in ASD does not appear to be associated with increased difficulty on aspects of cognitive attention, suggesting that different brain networks may underlie difficulties in these areas.