Daytime sleep duration during infancy as an indicator for cognitive development at school age: a prospective cohort study

Study Objectives: The reduction in daytime sleep during early life is considered one of the indicators of the maturation of sleep patterns, which is closely associated with cognitive development. The current study aims to analyze the relationships between daytime sleep duration (DSD) during infancy and cognitive development at 6 and 10 years. Methods: The study included 262 mothers with their newborns from the Shanghai Sleep Birth Cohort Study, spanning 11 follow-ups from 42 days to 10 years. Sleep parameters were assessed using parent-reported questionnaires at each follow-up, and cognitive development was evaluated with the Wechsler Intelligence Scale for Children, fourth edition at 6 and 10 years. Results: Two distinct DSD trajectories in early childhood were identified: "typical DSD " (66.7%) and "infancy excessive DSD " (33.3%). Children in the "infancy excessive DSD " trajectory exhibited lower working memory scores than those in the "typical DSD " trajectory at 6 years (mean difference = 5.90, 95% confidence interval [1.83, 9.96], P = .005) and 10 years (mean difference = 4.37, 95% confidence interval [0.26, 8.48], P = .037). Additional analysis in a relatively homogeneous sample consistently showed correlations between DSD trajectories and working memory performance. No consistent significant differences were found in other domains of cognitive development. Conclusions: Excessive daytime sleep during infancy may serve as an early indicator for poor working memory at school age. These findings raise concerns about the long-term cognitive development of infants with excessive DSD.