Inter- and intra-variability of sleep patterns in infancy and early childhood

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Sleep is one of the major sources of brain activity in childhood and plays a crucial role in neurodevelopment. In children and adults, shorter nocturnal sleep duration is associated with poorer cognitive performance. However, this relationship remains to clarify in infancy. Moreover, our work and others have shown major inter-variability and intra-variability in infant sleep patterns. This variability was only studied for specific sleep variables or with subjective variables, or during a few nights. Therefore, more work is needed to understand the variability of sleep variables in infancy, as well as its evolution across development. The long-term goal of this research program is to advance knowledge on the sleep-wake cycle variability across development, from infancy to adolescence, as well as the interplay between sleep variability and cognitive development. The short-term goals of this present proposal are to: AIM 1: To characterize sleep patterns variability within the same individuals during a two-week period of consecutive nights, using objective sleep measurements (actigraphy) and several sleep variables (duration, fragmentation). Hypothesis 1.1 High inter-variability will be observed between the different individuals. Within the same participants, sleep variables will also show high variability. Hypothesis 1.2 Variables linked to fragmentation will show higher inter- and intra-variability than variables linked to duration. AIM 2: To evaluate if sleep variability remains stable throughout development (using a longitudinal design with multiple timepoints - 3, 6, 12, 24, 36 months). Hypothesis 2.1 Variability will be observed at all timepoints, but it will decrease over time. Hypothesis 2.2 The rank of a specific infant will remain stable over time. AIM 3: To investigate which sleep variables are specifically predicting cognitive function at different stages of development (both concurrently and longitudinally). Hypothesis 3.1 Sleep consolidation at 6 months will not predict cognitive function at 6 months nor at 36 months. Hypothesis 3.2 Sleep duration at 36 months will predict cognitive function at 36 months old. Hypothesis 3.3 Considering the small number of studies on that topic, an exploratory analysis of the association between sleep patterns variability and cognitive function will be conducted (6, 36 months). Considering the major and accelerated development of sleep and cognitive functions in the first years of life, this program of research will advance our mechanistic understanding of these dynamic processes and their interaction. I am well prepared to undertake this proposed program in my laboratory, with my team of HQP. The results are expected to significantly advance the fields of sleep and developmental neuroscience in describing and understanding the importance of sleep patterns variability in infancy. The program will also offer to students a unique training opportunity, at different stages of training.