Association of Nighttime Sleep Duration at 1.5 Years with Height at 3 Years: The Japan Environment and Children's Study

Context: Adequate nighttime sleep duration has been considered beneficial for linear growth in children; however, there is limited and conflicting evidence regarding the association between sleep duration and subsequent linear growth.

Objective: To investigate the association between sleep duration at 1.5 years and height at 3 years of age.

Methods: The Japan Environment and Children's Study is a nationwide prospective birth cohort study. Data from 52,140 term singleton births born at an appropriate-for-gestational age without background disorders that could potentially affect linear growth in the analyses were included. Nighttime and total sleep durations were calculated based on a self-administered questionnaire completed by caregivers. Tall stature was defined as height at or above the 75th percentile among participants.

Results: After adjustment for height at 1.5 years, sex, monthly age, mother's height, presence of siblings at 1.5 years, environmental tobacco smoke at 1.5 years, daily TV/DVD screen time at 2 years, attendance at nursery at 2 years, household annual income at birth, and parents' educational status, multivariate odds ratio (95% confidence interval) for tall stature at 3 years were 1.09 (1.01-1.17), 1.09 (1.01-1.17), and 1.25 (1.14-1.37) for 9.5 or 10, 10.5 or 11, and ≥ 11.5 h of nighttime sleep duration at 1.5 years, respectively, compared with those with ≤ 9 h sleep (p for trend <0.0001). Total sleep duration was not associated with tall stature.

Conclusion: This study underscores the importance of nighttime sleep duration, not total sleep duration, in the linear growth of very young children.