Association between sleep duration and child development: the Japan Environment and Children's Study

Few studies have examined the association between total sleep duration and general child development, as well as the environmental factors influencing sleep duration among children. To elucidate this issue, we investigated the association between sleep duration, child development, and the sleep environment. We used data from an ongoing nationwide prospective birth cohort study in Japan. Developmental delays were measured using the Ages and Stages Questionnaires, third edition (ASQ-3). Sleep duration was assessed using a questionnaire completed by the children's caregivers. To assess the associations, we performed logistic regression and generalized linear mixed model analysis. Shorter sleep duration (< 10 h) at multiple time points was associated with an increased likelihood of developmental delay at 3 years of age (Sleep@6 m: Odds ratio (OR) 1.11, p < 0.001; Sleep@1y: OR 1.09, p = 0.01; Sleep@3y: OR 1.15, p < 0.001). These associations were still observed after adjusting for individual characteristics and relevant covariates (coefficient: 0.054; p < 0.001). In analyses examining the sleep environment, sleep location was associated with shorter sleep duration, whereas other environmental factors showed no significant associations (coefficient: 0.13; p = 0.049). These findings suggest that shorter sleep duration during early childhood is associated with developmental outcomes and that sleep location may be related to sleep duration. Further studies are needed to clarify the underlying mechanisms and potential bidirectional relationships involved.