Associations between a 24-hour movement behaviour composition including screen time and physical development in pre-schoolers

Abstract Background It remains unclear how movement behaviour compositions that include screen-based sedentary behaviour (SED) and non-screen-based SED relate to physical development in young children. This study examined associations between a five-component time-use composition, including moderate-to-vigorous-intensity physical activity (MVPA), light-intensity physical activity (LPA), screen-based SED, non-screen-based SED, and sleep, and key physical development indicators in an international sample of pre-schoolers, and estimated optimal time-use compositions. Methods Participants were 4,856 pre-schoolers (mean age = 52.6 ± 9.0 months) from the Sleep and Activity Database for the Early Years (SADEY). MVPA, LPA, and total SED were measured using accelerometery, while screen time and sleep were parent-reported. Screen time was operationalised as occurring while sedentary and subtracted from total SED to derive non-screen-based SED. Physical development indicators included body mass index z-score (zBMI), waist-to-height ratio (WHtR), systolic and diastolic blood pressure, and locomotor, object control, and overall gross motor skills. Compositional data analysis was used to examine associations, model time reallocations, and estimate optimal time-use compositions. Results The five-component time-use composition was associated with all physical development indicators except for locomotor skills, explaining small proportions of variance (marginal R 2 = 0.01–0.11). Across component time reallocations ranging from − 60 to + 60 min, generally small favourable dose-response associations were observed for reallocations to MVPA (WHtR; diastolic blood pressure; object control skills; overall gross motor skills) and sleep (WHtR; object control skills; overall gross motor skills). Reallocations of screen-based SED showed predominantly null associations, reallocations of non-screen-based SED showed mixed associations, and reallocations of LPA showed generally unfavourable associations. The estimated multidomain optimal composition corresponded to 129 (110–150) min/d of MVPA, 250 (230–270) min/d of LPA, 78 (50–130) min/d of screen-based SED, 389 (330–470) min/d of non-screen-based SED, and 594 (560–640) min/d of sleep. Conclusion The five-component time-use compositions showed associations, generally small in magnitude, with key physical development indicators in pre-schoolers. Among time-use behaviours, prioritising both MVPA and sleep appears a beneficial strategy for supporting physical development, such as healthy adiposity, blood pressure, and gross motor skills, in this age group.