Changes in 24-hour movement behaviours during the transition from primary to secondary school among Australian children

This study examined concurrent changes in all components of 24-h movement behaviours (24-h MB) (sleep, sedentary behaviour [SB] and physical activity [PA]) and compliance with the Australian 24-Hour Movement Guidelines over the primary to the secondary school transition period. The analytical sample included 83 children (60.2% girls) who provided valid accelerometer-measured 24-h MB data during their final year of primary school (T1) and first year of secondary school (T2). Self-reported participation in domain-specific SB and PA, socio-demographic characteristics and weight status were also assessed. Change in 24-h MB composition from T1 to T2 was analysed using a compositional multivariate linear model for repeated measures. The difference in the proportion of meeting the 24-hour integrated movement guidelines was assessed using a McNemar-Bowker test. An unfavourable change was observed in the 24-h MB composition (p < .0001), with increased time spent in SB (+58 min/day) and decreased time in sleep (-13 min/day), Iight-intensity PA (-13 min/day) and moderate- to vigorous-intensity PA (-14 min/day). Domain-specific SB results indicated an increase in recreational screen time (+45 min/day) and out-of-school educational activities (+25 min/day). No significant changes were observed for domain-specific PA. The proportion of children meeting the 24-hour integrated movement guidelines also declined (20.5% vs. 3.6%; p < .0001). Change in 24-h MB was larger on weekdays than weekends (p < .0001); but this was not moderated by socio-demographic characteristics or weight status. These findings suggest that an integrated intervention approach targeting weekdays may be beneficial to promote adherence to healthy 24-h MB during the primary to the secondary school transition period.