Landmark Australian Study Tracks How Children Move, Sleep and Sit From Toddlerhood to Teens

Only 8 percent of preschool-aged children meet all three components of Australia’s 24-hour Movement Guidelines for the Early Years, according to new findings from one of the world’s largest longitudinal studies of children’s movement behaviours. The finding comes from the PLAY Spaces and Environments for Children’s Physical Activity, Sedentary Behaviour and Sleep (PLAYCE) cohort study, a decade-spanning research programme in Western Australia that has now published a detailed profile of its methods, participants and results in the Journal of Activity, Sedentary and Sleep Behaviors. The study follows nearly 2,000 children from their preschool years into early adolescence, combining wearable sensors, satellite positioning, geographic mapping and parental surveys to build one of the most comprehensive pictures ever assembled of how young children move through their days, and how the places they inhabit shape those patterns.

The PLAYCE cohort was established to address a fundamental gap in child health research. Childhood is a critical period for establishing movement behaviours, including regular physical activity, adequate sleep and limited sedentary time, and these behaviours provide the foundation for lifelong health. They influence weight status, cardiorespiratory fitness, the musculoskeletal system, and cognitive and psychosocial development. Yet most research on children’s movement behaviours has been cross-sectional, capturing a single moment in time rather than tracking how behaviours change and interact as children grow. Australia and Canada were the first countries to release integrated 24-hour movement guidelines for young children in 2018, treating physical activity, sedentary behaviour and sleep as three co-dependent behaviours rather than isolated targets. Meeting all three recommendations together is considered optimal for child health, but until now it has been unclear whether children who achieve this balance in their early years sustain it as they move into middle childhood, or what that trajectory means for their health and development.

The scale of the measurement challenge is considerable. Between April 2015 and April 2018, researchers recruited 1,918 children aged 2 to 5 years through early childhood education and care services across Perth, Western Australia. Services were randomly sampled and evenly distributed across low, medium and high socio-economic areas and across service sizes. Of 273 services invited, 126 directors consented, a response rate of 46.2 percent. At the first wave, the median age of participating children was 3.3 years and 53 percent were male. The cohort has since been followed through junior primary school at ages 5 to 7, middle childhood at ages 8 to 10, and a fourth wave of data collection at ages 11 to 13 is underway and expected to be completed in early 2026. In total, 434 children have participated at all three completed waves, providing the kind of sustained individual tracking that longitudinal behavioural science depends on.

The technical core of the study is its use of ActiGraph GT3X+ accelerometers, small devices worn on the right hip that record acceleration in three dimensions. Children wore the devices for seven consecutive days, initially excluding water activities and sleep, and from the second wave onward across the full 24-hour cycle to capture sleep as well as waking movement. Valid wear time was defined as a minimum of eight hours on at least three weekdays and one weekend day. Rather than relying on traditional cut-point methods, which classify activity intensity using fixed thresholds, the researchers applied a random forest machine learning model to the raw tri-axial acceleration signals. This algorithm classifies behaviour into sedentary activity, light-intensity games, walking, running and moderate-to-vigorous activity with an overall accuracy exceeding 80 percent, agreeing more closely with measured intensity than cut-point approaches and showing equivalence with direct observation. The distinction matters because young children’s activity is notoriously sporadic and difficult to categorise, and more accurate classification yields a sharper picture of the actual doses and combinations of movement linked to health outcomes.

The environmental measurement is equally ambitious. A subset of 237 children at the first wave also wore Qstarz GPS devices on the same belt as their accelerometers, recording location coordinates, distance, speed and elevation with a median dynamic accuracy of 2.9 metres. Combining these spatial traces with Geographic Information Systems data allowed researchers to calculate measures around each child’s home and care centre, including outdoor space, vegetation, public open space quality, blue space, traffic exposure, public transport, street connectivity, residential density and access to child-relevant services, all within 500-metre and 1,600-metre buffers. Physical and policy audits of early childhood education and care centres assessed indoor and outdoor play spaces, play and media equipment, built and natural features, and the presence of service policies on physical activity, screen time and sun protection. Educator surveys captured staff practices, and parent surveys recorded structured and unstructured activity, sleep, screen time, diet, social-emotional development measured with the Strengths and Difficulties Questionnaire, motor development, and neighbourhood perceptions using the Neighbourhood Walkability Scale for Youth.

The baseline results are striking. On average, preschoolers in the cohort accumulated 373 minutes of total physical activity per day, of which just 39.1 minutes was energetic play such as running and vigorous games. They averaged 106.9 minutes of daily screen time and 11.5 hours of sleep. Individually, 42 percent met the physical activity guideline, 67 percent met the screen time recommendation and 92 percent met the sleep guideline, but only 8 percent satisfied all three simultaneously. Meeting all three recommendations was positively associated with social-emotional development in boys, consistent with emerging international evidence that the combination of behaviours, not any single behaviour alone, drives developmental benefit. Other analyses from the cohort have linked moderate-to-vigorous physical activity with self-regulation and cognitive school readiness, and shown that children from dog-owning households had reduced odds of social-emotional problems, with those who walked or played with their dog more often showing improved prosocial behaviours.

The environmental findings offer concrete design clues. Features of the home yard, including its size, the presence of play equipment and natural features, were positively associated with preschoolers’ outdoor play. At childcare centres, tree canopy in outdoor areas served both as sun protection and as an enabler of children’s outdoor time, while more portable play equipment was linked to greater outdoor activity. A novel analysis combining accelerometer, GPS and on-site audit data mapped physical activity hot spots within centres, finding them concentrated in open areas and adjacent outdoor play spaces where children could move freely between them. Air pollution monitoring revealed a troubling overlap: pollution concentrations at childcare centres were highest at exactly the times children were likely to be active outdoors, prompting a recommendation to avoid locating services in high-traffic areas. Neighbourhood perceptions mattered too, with parents’ positive views of traffic safety, crime safety and land use mix associated with lower odds of social-emotional difficulties in their children.

The study has not been without challenges. Retention fell to 39.9 percent of eligible and contactable participants at wave 2 and 38.7 percent at wave 3, reflecting the three-year recruitment window that left some children outside the age criteria for follow-up, the disruption of COVID-19 restrictions during wave 2 data collection, and the time burden of parental questionnaires. The researchers note, however, that the representativeness of the sample remained largely unaffected and the cohort remains sufficiently powered for longitudinal analyses. The study is limited to a single site in Perth and underrepresents families with lower relative socio-economic status, single-parent households, First Nations families and culturally and linguistically diverse communities, gaps the team identifies as priorities for future research. A community-based consumer reference group of parents now provides input into recruitment, methodology and the translation of findings, meeting at least three times a year.

As the fourth wave concludes, the team plans traditional longitudinal and compositional analyses to map in detail how movement behaviours shift across the transition from early childhood education to full-time school, a period when previous small studies have recorded increases of around 40 minutes of daily sedentary time and declines in physical activity. Whether those changes are permanent or transitional remains unknown, and the PLAYCE data should answer it. The findings are expected to inform future revisions of national and international 24-hour Movement Guidelines, which have called for more rigorous and consistent accelerometer processing methods, and to guide setting-specific and population-level interventions, from childcare policy to neighbourhood design, aimed at curbing childhood obesity and ensuring children have the opportunity to lead active, healthy lives from their earliest years through adolescence.

Subject of Research: A longitudinal cohort study of children's physical activity, sedentary behaviour and sleep across early to middle childhood in Western Australia

Article Title: Profile of the PLAY spaces & environments for children’s physical activity, sedentary behaviour and sleep (PLAYCE) cohort study, Western Australia

Article References: Christian, H., Nathan, A., Trost, S. G., Schipperijn, J., Boruff, B., Adams, E. K., George, P., Moore, H. L., & Henry, A. (2025). Profile of the PLAY spaces & environments for children’s physical activity, sedentary behaviour and sleep (PLAYCE) cohort study, Western Australia. Journal of Activity, Sedentary and Sleep Behaviors, 4(1), Article 7. https://doi.org/10.1186/s44167-025-00078-8

Image Credits: AI Generated

DOI: 10.1186/s44167-025-00078-8

Keywords: PLAYCE cohort study, children's physical activity, sedentary behaviour, sleep, 24-hour movement guidelines, accelerometry, built environment, early childhood education, child development, obesity, GPS tracking, Western Australia