Compositional analysis of the associations between 24-hour movement behaviours, motor skills, and executive function in Mongolian preschool children

Evidence is limited on 24-hour movement behaviour composition and health outcomes among children under 5 from low- and middle-income countries. This study aimed to explore movement behaviour composition of Mongolian preschoolers and its associations with motor skills and executive function. This cross-sectional study measured movement behaviours (physical activity, sedentary behaviour, and sleep) using ActiGraph accelerometers for 5 weekdays among 201 preschool children (3-5 years) from Mongolia. Motor skills and executive function were assessed using established tools. Compositional linear regression and isotemporal substitution models were employed to explore movement behaviour associations and reallocation effects on health outcomes. Movement behaviour composition was significantly associated with motor skills but not with executive function. Moderate-to-vigorous physical activity (MVPA) showed strongest favourable associations with motor skills. Largest effect sizes occurred when 30 minutes were reallocated to MVPA from light physical activity: lower body strength (ES = 0.64; CI = 0.22, 1.05); upper body strength (ES = 0.72; CI = 0.28, 1.15); and dexterity (ES = -0.50; CI = -0.95, -0.05) [favourable]. Reallocating time to light physical activity from other behaviours was associated with poorer strength outcomes. Time distribution across 24-hour movement behaviours impacts preschoolers' motor development. Public health policy and interventions should prioritise MVPA among young children by leveraging kindergarten settings.