This study aimed to examine the associations between sleep duration, adiposity indicators, and cognitive development in young children.
Participants were 217 children aged 19-60 months in Canada in the supporting Healthy physical AcTive Childcare setting (HATCH) study. Nap duration and nighttime sleep duration were assessed using a parent questionnaire and were summed up as total sleep duration. Body mass index (BMI) z-scores and weight status were determined using the World Health Organization growth standards. Expressive vocabulary and working memory were assessed using the Early Years Toolbox in preschoolers only (36-60 months; n = 101). Mixed models (BMI z-score, expressive vocabulary) and generalized mixed models (weight status, working memory) were conducted.
A linear association between total sleep duration and BMI z-score (B = -0.12; 95% CI: -0.23, -0.01) were observed. Compared to children having nighttime sleep within ±1SD (9.13-11.13 h/d) of the mean, those having shorter nighttime sleep had higher BMI z-scores (B = 0.39; 95% CI: 0.06, 0.73) and an increased risk of being overweight (OR = 4.54; 95% CI: 1.39, 14.81). Nap duration was not associated with adiposity indicators. In preschoolers, sleep duration was not associated with expressive vocabulary. Total sleep duration and nap duration were not associated with working memory. However, non-nappers were more likely to have greater working memory (OR = 4.04; 95% CI: 1.09, 14.92) compared to those having nap duration within ±1SD (0.46-2.18 h/d) of the mean.
Promoting longer total sleep, including more than nine hours of nighttime sleep, appears important for maintaining healthy adiposity levels in young children. Cessation of napping may be associated with better working memory in preschoolers.

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