Several studies have demonstrated that sleep during the early years (i.e. prior to formal school entry) can predict later language skills, cognition and wellbeing during childhood and adolescence. However, these studies have typically only examined a few sleep parameters (e.g. Dionne et al., 2011; Knowland et al., in press;), with some mixed findings emerging (Kocevska et al., 2017; Touchette et al., 2007). Moreover, research exploring the effects on later mental wellbeing have generally relied on a composite ‘sleep problems’ variable (reflecting various individual sleep parameters; e.g. frequent wakings, early wakings, nightmares; e.g. Gregory & O’Connor, 2002), making it difficult to conclude which sleep parameters are important. Further research is therefore needed to systematically examine the effects of early sleep on these critical cognitive and wellbeing outcomes. Nevertheless, based on existing evidence, it appears that sleep quality and quantity parameters can predict key outcomes during childhood and adolescence.

However, the effects of early sleep have only been considered on a limited number of outcomes to date. Notably, extant investigations into the effects of sleep on cognitive outcomes have relied on standardised test performance. It is therefore unclear whether early sleep parameters predict real-world cognitive outcomes, such as educational performance. Although there is evidence that sleep parameters are predictive of school readiness and academic achievement (e.g. Drake et al., 2003; Tso et al., 2016), these studies have either been cross-sectional in nature (measuring sleep close in time to the educational assessments) or longitudinal studies that commenced at or after the point of school entry. Longitudinal investigations of the effects of early sleep (i.e. before school entry) on later educational outcomes are lacking. The planned research will address these questions, by examining whether sleep during early development (i.e. at 6-42 months of age) predicts performance on a school entry assessment and academic achievement.

The project will also investigate factors that drive the effects of early sleep on later educational outcomes. As school readiness and academic achievement are closely linked to language abilities, cognitive skills, and mental wellbeing (e.g. Agnafors et al., 2020; Duncan et al., 2007; Romano et al., 2010), these factors may mediate the relationship between early sleep and educational outcomes. Alternatively, or additionally, it is possible that the longitudinal effects on educational outcomes may be driven by persistent sleep patterns. Indeed, there is some evidence that sleep parameters show continuity throughout childhood and adolescence (e.g. Stein et al., 2001). As such, it is possible that early sleep patterns may predict sleep parameters measured close in time to the school readiness and academic assessments, with sleep at these latter timepoints affecting educational performance. The current research will investigate these research questions by: (i) further examining how early sleep relates to language, cognitive, and wellbeing outcomes at school entry; and (ii) investigating whether these factors drive the relationship between early sleep and later educational outcomes.

Finally, from both a theoretical and practical perspective, the project will examine whether effects of sleep are equivalent for different groups of children. As cross-sectional studies have found that sleep is particularly important for cognitive functioning and academic outcomes in children from disadvantaged backgrounds (e.g. Wetter et al., 2019), this analysis will focus on examining whether the longitudinal effects of early sleep are moderated by maternal education and self-reported financial difficulties.