Peer-reviewed article
Association of Nighttime Sleep Duration at 1.5 Years With Height at 3 Years: The Japan Environment and Children's Study.
Masanobu Kawai, Sachiko Baba, Kanami Tanigawa, Satoyo Ikehara, Ryo Kawasaki et al. ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study examined whether nighttime sleep duration at 1.5 years of age is associated with height at 3 years in Japanese children. Using data from over 52,000 children in a national birth cohort study, researchers found that children who slept longer at night (10 or more hours) were more likely to be taller at age 3, even after accounting for their height at 1.5 years and other factors. Interestingly, total sleep duration (including daytime naps) was not associated with height growth. The findings suggest that nighttime sleep, rather than overall sleep amount, may be important for normal growth in young children.
Key points
- Children sleeping ≥11.5 hours per night at 1.5 years were 1.25 times more likely to have above-average height at 3 years
- The association was dose-dependent: each additional hour of nighttime sleep was associated with incrementally higher odds of tall stature
- Total sleep duration (nighttime plus daytime naps) showed no significant association with height
- Results remained significant after adjustment for height at 1.5 years, parental height, socioeconomic factors, and environmental exposures
- The study included 52,140 term singleton births without conditions affecting growth
Limitations
The study uses caregiver-reported sleep duration from questionnaires, which may be subject to recall bias or inaccuracy. The cross-sectional nature of the sleep measurement at one timepoint cannot establish causality, and unmeasured confounders related to sleep quality or family sleep practices may influence the results.
Abstract
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% CI) 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 hours of nighttime sleep duration at 1.5 years, respectively, compared with those with ≤ 9 hours sleep (P for trend <.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.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Adequate nighttime sleep duration (≥10 hours per night)
- Population
- 52,140 Japanese term singleton births without growth-affecting conditions, assessed at 1.5 years and followed to 3 years
Key finding
Children with ≥11.5 hours nighttime sleep at 1.5 years had multivariate OR 1.25 (95% CI 1.14-1.37) for tall stature at 3 years versus those with ≤9 hours
Kawai et al. · PubMed (US National Library of Medicine) · 19 May 2025