Sleep and Movement Behaviours in Preschool Children: A Cross-Sectional Study With Compositional Data Analysis.

Reciprocal relations between physical activity and sleep in early childhood are inconsistent relative to reports in adolescents and adults. Compositional data analysis research highlights the need to examine 24-h behaviours holistically. Yet, studies often focus on daytime metrics, neglecting sleep components. This study aimed to determine if the compositions of overnight sleep, 24-h sleep, and nap sleep stages are associated with physical activity in preschool children and if behaviours of a complete 24-h cycle (sleep and wake) vary by sex or nap habituality. Actigraphy data pooled from two studies (n = 272 children; 4.2 ± 0.8 years) provided estimates of sleep and physical activity. Night and 24-h sleep composition included sleep onset latency, duration, and wake after sleep onset. Nap sleep was measured in 31 children with polysomnography (wake and non-REM sleep stages 1, 2 and 3). Nap sleep stage compositions were not associated with movement behaviours. Six multivariate regression models explored differences in compositional 24-h time use between sex and nap habitually groups. Time-use compositions that included both wake and sleep components varied by age, sex, and nap habituality for all components except total sleep time. This study demonstrates the value of CoDA for understanding 24-h behaviour patterns, revealing that nap habits, age, and sex are linked to specific sleep and activity components in preschoolers. Future research should explore these compositional associations in more diverse populations, consider additional physical activity indicators, and incorporate overnight polysomnography assessments.