The rate and prevalence of childhood obesity and its associated morbidities, such as obstructive sleep apnoea (OSA), is increasing. Sleep disruption due to OSA has been associated with neurobehavioural impairments such as less well intelligence, memory, behaviour and executive function in younger children. However, neurobehavioural studies in obese children are lacking. Thus, the first of two main studies in this thesis, the obesity study, aimed to establish a detailed description of neurobehavioural problems that can arise due to OSA occurring in obese adolescents. There is growing evidence of the relationship between short sleep duration and risk for obesity with the dysregulation of appetite hormones leptin and ghrelin thought to be a contributing factor. However, no study that we are aware of, has looked at a sleep-only intervention as a potential weight management tool in children. Thus, the second main study, the sleep study, aimed to examine the effectiveness of a sleep-hygiene-only intervention on improving sleep hygiene, sleep quality and daytime symptoms in youth.
Methods and Results: In the obesity study, 31 participants aged 13.7 (SD ±2.49) years, with a mean (SD) BMI z-score of 3.0 (0.68) were classified into OSA (AHI ≥ 1) and non- OSA (AHI < 1) groups using overnight polysomnography (PSG). The mean (SD) obstructive AHI obtained for the OSA and non-OSA group was 4.69 (3.72) and 0.49 (0.32) respectively. Intelligence, memory & learning, academic achievement, behaviour and executive function were assessed using the Weschler Abbreviated Scale of Intelligence (WASI), Wide Range Assessment of Memory and Learning 2 (WRAML-2), Weschler Individual Achievement Test II (WIAT-II), Behavioural Assessment System for Children 2 (BASC-2) and Behavior Rating Inventory of Executive Function (BRIEF) respectively. Performance scores across most measures were statistically (but not clinically) significantly less well than the normative mean. There was also a non-significant tendency for the OSA group to perform less well across most measures compared to the non-OSA group. This seems to indicate possible additive impairments in obese children with OSA compared to their non-apenic but obese counterparts. In the sleep study, we first developed an age-appropriate sleep hygiene programme in consultation with children (10-18 years old) and then piloted this programme in 33 other children of the same age-group (mean age ±SD 12.9 ±2.19) and found significant improvements, 20 weeks post-intervention, in sleep hygiene as assessed by the Adolescent Sleep Hygiene Scale (0.19, CI 0.06 to 0.33; p = 0.005), sleep quality as reflected in the Pittsburgh Sleep Quality Index (-2.93, CI -3.61 to -2.24; p < 0.001) and Sleep Disturbances Scale for Children (-14.1, CI -17.1 to -11.1; p < 0.001) as well as daytime sleepiness as reflected in the Pediatric Daytime Sleepiness Scale (-5.1, CI -7.0 to -3.2; p < 0.001). A small but statistically significant decrease in BMI z-scores (-0.13, CI -0.20 to 0.05; p = 0.001) and sedentary/light energy expenditure (-27, CI -50 to -3; p = 0.025) were also observed.
Conclusion: Findings from the obesity study suggest that obese children tend to perform less well on neurobehavioural assessments compared to the normative population and that there is a non-significant but consistent pattern of even less well performance in the combined obesity-OSA condition. Findings of the sleep study suggest that the sleep hygiene programme developed is effective in improving sleep hygiene and quality, but more importantly highlights the potential of sleep hygiene for weight management in youth. Indeed, a follow-up randomised controlled trial investigating the long term effects of a sleep hygiene intervention on physiological, psychological and behavioural health outcomes in obese youth has been proposed and is currently being considered.
