The moderating role of subjective daytime sleepiness in the associations between sleep duration and brain morphology in school-aged children

Study Objectives The alignment between greater sleep demands and heightened neuroplasticity in childhood suggests that sleep plays a key role in brain maturation. While sleep duration is commonly accepted as a marker for adequate sleep, this indicator overlooks differences in individual sleep needs. Subjective perception of sleepiness may offer additional insight into sleep insufficiency relative to individual needs. This study aimed to investigate the associations between sleep duration and brain morphology in typically developing children, and the moderating effect of subjective sleepiness in these associations.Methods In 81 children (45 boys, 10.53 years old), actigraphy-derived estimates of sleep duration were obtained over 5-7 days, and subjective daytime sleepiness was self-reported. Gray matter volume (GMV) was estimated for 11 brain regions. Linear associations between sleep duration and regional GMV were tested, along with the interaction between sleepiness and sleep duration in relation to regional GMV.Results Sleep duration negatively correlated with GMV in the insula at the group level. Subjective sleepiness moderated the relationship between sleep duration and GMV, with associations found in the hippocampus and middle temporal gyrus for children prone to sleepiness, and in the precuneus for those without sleepiness.Conclusions The current results suggest that normative variations in sleep duration may bear on child brain morphology, with distinct associations at varying levels of subjective daytime sleepiness in regions subsuming executive functioning and memory consolidation. These findings highlight the importance of incorporating both objective and subjective aspects of sleep in future research on sleep health and neurodevelopment.