Title: Sleep and its relation to cognition and behaviour in preschool-aged children of the general population: a systematic review

Abstract: Background: While the relations between sleep, cognition and behavior have been extensively studied in adolescents and school-aged children, very little attention has been given to preschoolers. Objective: In this systematic review, our aim was to survey articles that address the link between sleep and both cognition and behavior in preschoolers (24 to 72 months old). Methods: Four electronic databases were searched, namely Medline, Web of Science, PsycINFO and ERIC, completed by forward and backward citation search. Results: Among the 1590 articles identified (minus duplicates), 26 met the inclusion criteria. Globally, studies with the largest sample sizes (N=13) found that a greater quantity or quality of sleep was associated with better behavioral and cognitive outcomes, while the others were less consistent. Conclusion: Although the current literature seems to indicate that sleep is related to behavioral and cognitive development as early as preschool years, the strength of the associations (i.e. effect sizes) was relatively small. In addition to taking stock of the available data, this systematic review identifies potential sources of improvement for future research.