Sleep variability and learning outcomes in preterm and full-term children: An observational study

Advances in perinatal care have improved survival rates of preterm infants; however, concerns regarding their neurodevelopmental outcomes persist. This study investigates the relationship between intraindividual variability (IIV) in sleep duration and crystallized intelligence in very low birth weight (VLBW) children at the preschool stage. This study had 38 participants, including 18 VLBW children and 20 full-term children aged 5 to 6 years. Sleep duration was assessed using actigraphy and sleep diaries, while crystallized intelligence was evaluated using the Achievement Scale (ACH) of the Kaufman Assessment Battery for Children (K-ABC). Statistical analyses, including correlation and multiple regression analyses, were conducted to examine the effect of preterm birth on the relationship between sleep variability and learning outcomes. The results revealed that sleep duration IIV adversely affected ACH scores of preterm children but had no impact on those of full-term children. In multiple regression analysis, the interaction term between sleep variability and preterm birth significantly predicted ACH scores (p = 0.032), suggesting that early childhood learning in preterm children is more vulnerable to the effects of sleep instability. Additionally, among VLBW children, older age was associated with lower ACH scores, implying that learning difficulties may become more pronounced with age. These results show the potential role of sleep regulatory mechanisms in cognitive development. The findings show the importance of monitoring and supporting healthy sleep habits in preterm children to mitigate potential learning difficulties. Early interventions targeting sleep stability may play a critical role in improving academic performance in this high-risk population.