Impact of sleep duration on daytime sleepiness in children: A meta-analysis.

Whilst previous reviews have identified that shorter sleep duration is associated with poorer cognition in children, it is not known whether short sleep duration increases daytime sleepiness compared with sufficient or extended sleep. A systematic search of the literature identified 17 studies to be included in the meta-analysis. When excluding two sleep deprivation studies, short sleep duration was associated with higher daytime sleepiness compared with sufficient or extended sleep duration, standardised mean difference: 0.74 (95 % CI 0.45; 1.02). There was substantial variation in the extent of sleep restriction in the short sleep duration group compared to the sufficient/extended group. This was a significant moderator, accounting for 7 % of the effect size. As the effect size was lower for children compared to adolescents, it suggests that adolescents are particularly vulnerable to the effects of short sleep. For individual studies, the standardised mean difference had wide confidence intervals, suggesting that there are substantial inter-individual differences in response to short sleep duration compared to sufficient sleep duration. Further research is needed to identify whether daytime sleepiness mediates the relationship between sleep duration and cognitive outcomes.