Sleep During Infancy, Inhibitory Control and Working Memory in Toddlers: Findings from the FinnBrain Cohort Study

Abstract

Background: Sleep difficulties are associated with executive functioning (EF) impairment in school-aged children. However, much less is known about how sleep in infancy relates to EF in infants and/or toddlers. The aim of this study was to investigate whether parent-reported sleep patterns in infants at 6 and 12 months of age were associated with inhibitory control (IC) and working memory (WM) performances at 30 months. Methods: The children were divided into three sleep groups (i.e., “bad sleepers”, “intermediate sleepers” and “good sleepers”) based on percentile cut-off points in order to have a comprehensive understanding of the direction and nature of the associations between sleep and aspects of EF in early childhood. Sleep was assessed using the Brief Infant Sleep Questionnaire, IC was measured using a modified version of the Snack Delay task (N=425), and WM by using the Spin the Pots task (N=430). Results: Our results reported an inverted U-shaped association between proportion of daytime sleep at 12 months and IC at 30 months, indicating that average proportions of daytime sleep were longitudinally associated with better IC performance. Furthermore, a linear relation between time awake during night at 12 months and WM at 30 months was found, with more time awake at night associating with worse WM. Conclusions: Our findings support the hypothesis that sleep disruption in early childhood is associated with the development of later EF and suggest that different sleep difficulties at 12 months distinctively affect WM and IC in toddlers, possibly also in a non-linear manner.