Isotemporal substitution analysis of the effects of in-kindergarten structured and unstructured activity behaviors on sleep problems in preschool children

OBJECTIVE: Using an isotemporal substitution model, this study analyzed the mutual substitution relationships among structured and unstructured physical activities of different intensities and sedentary behavior in kindergarten settings, and explored their associations with sleep problems in young children. METHODS: A cross-sectional sample of 336 children aged 3-6 years was recruited. Five behavioral variables-SB, S-LPA, US-LPA, S-MVPA, and US-MVPA (LPA, light physical activity; MVPA, moderate-to-vigorous physical activity)-were measured using video observation, accelerometry, and a standardized assessment tool. Sleep problems were assessed with the Children's Sleep Habits Questionnaire (CSHQ). Linear regression and isotemporal substitution models were used to analyze the data. RESULTS: Univariate model results showed that US-LPA (β=-0.440, 95%CI:-0.829 to -0.050, P = 0.027) and US-MVPA (β=-0.598, 95%CI:-1.092 to -0.104, P = 0.018) were significantly negatively associated with total sleep problems in preschool children. S-MVPA (β=-0.110, 95%CI:-0.212 to -0.008, P = 0.034) and US-MVPA (β=-0.064, 95%CI:-0.122 to -0.007, P = 0.029) were significantly negatively associated with SOD, and US-LPA (β=-0.172, 95%CI:-0.272 to -0.073, P = 0.001) and US-MVPA (β=-0.234, 95%CI:-0.361 to - 0.108, P < 0.001) were significantly negatively associated with SD. In the partition models and isotemporal substitution models, after Bonferroni correction, no other significant associations were observed. CONCLUSION: Increasing levels of unstructured LPA and unstructured MVPA helps preschool children maintain sufficient sleep duration and alleviate sleep onset delay, thereby improving their overall sleep problems.