Multi-method exploration of the relationship between sleep and infant neurocognitive development

The first year of life is a time of numerous developmental milestones. At the same time an infant’s sleep under goes many fundamental changes. Research has shown that sleep can impact aspects of development; however, findings are mixed, often fail to include objective measures of both development and sleep, and longitudinal studies are missing. This project uses a multi-method approach to exploring the relationship between sleep and neurocognitive development in the first year of life. For this purpose, longitudinal and cross-sectional experimental designs were combined with a multitude of objective and subjective methods (such as electroencephalography(EEG), actigraphy, eye-tracking, near-infrared spectroscopy(NIRS), parent-report questionnaires),and analysis approaches (cluster analysis, mixed modelling, and functional connectivity analysis). Key insights from the longitudinal study showed that cross-method agreement between different sleep measures varied depending on sleep parameters, infant age, and maternal stress. Moreover, sleep measurement choice can influence how the relationship between sleep and development is described. Associations with behavioural and parent-report measures of infant development were fragmented. However, a clearer cross-method consistent picture emerged with regard to brain measures that highlighted the importance of studying sleep fragmentation. The study also underscored the need to study the relationship between sleep and development continuously as there was evidence for age-related changes in the association between sleep and development. The second, cross-sectional study contributed a new methodology to studying the relationship between sleep (quality) and neurocognitive development. A customised NIRS-EEG system was used as a novel way to study infant brain activity during sleep. This project enables further research into sleep in a developmental context including the potential use of a wireless NIRS-EEG system to study sleep in naturalistic settings and of sleep fragmentation as a target for sleep-based interventions for children with neurodevelopmental disorders