Sleep and cognition in children with Down Syndrome and Williams Syndrome

This thesis provides a novel contribution to cognitive and developmental psychology by investigating\ud the relationship between sleep, behaviour and cognition in 41 healthy typically developing (TD)\ud children, 22 children with Down syndrome (DS) and 22 with Williams syndrome (WS). In addition,\ud developmental changes in sleep and cognition, and the importance of sleep for consolidation of new\ud memories were assessed in these groups. Finally, the influence of children's sleep and behaviour on\ud their mothers' sleep and wellbeing were examined. The research used a battery of standardised and\ud novel cognitive tasks, objective measures of sleep, and questionnaires.\ud Sleep problems were syndrome-specific, with poor sleep quality and oxyhaemoglobin desaturation\ud occurring more frequently in DS, suggestive of breathing difficulties during sleep, and long sleep\ud latencies in the WS group. TD children performed well on cognitive tasks of short term memory,\ud working memory and sustained attention compared to children with DS and WS, and their\ud performance generally improved with increasing age, which tended not to be the case for the clinical\ud groups. In the TD group, improved sleep quality and higher, less variable oxyhaemoglobin saturation\ud related to better performance on cognitive tasks and fewer behavioural problems. Few associations\ud between sleep, cognition and behaviour were found in the DS and WS groups. TD children and\ud children with WS showed evidence of sleep-dependent memory consolidation for explicitly learnt\ud material on two tasks. Mothers of children with DS had the poorest sleep and most daytime\ud sleepiness, though not related to children's sleep or daytime behaviour.\ud The findings indicate that sleep problems should be assessed and managed in clinical groups.\ud Educational strategies should be implemented to reinforce sleep-related learning gains. Future\ud research could examine whether sleep-dependent learning occurs in relation to specific aspects of\ud sleep architecture in children with DS and WS, as it does in adults and TD children