The objective of this study was to examine associations for adherence to 24-h movement guidelines with physical, cognitive, social-emotional, and overall development composite scores in a sample of 3–5-year-olds. Meeting the sleep recommendation was positively associated with overall development. Meeting both the sleep and physical development recommendations was positively associated with overall and physical development. Small effect sizes were found for all significant relationships. Further, no associations were observed for sedentary behaviour recommendations.
Positive associations between adherence to 24-h movement guidelines and indicators of physical development were found in a recent longitudinal study . Specifically, meeting the physical activity, sedentary behaviour, and sleep recommendations at age 3 to 5 years was associated with lower BMI z-scores at ages 9–11 years. In contrast, while the current study found associations for the physical development composite score, no associations were found specifically for BMI z-scores. Additionally, no associations were found between guideline adherence and BMI z-scores in a Canadian nationally representative cross-sectional sample of children aged 3–4 years  and a Swedish nationally representative longitudinal study of children 4 years of age, followed-up at 1 year . However, the lack of associations in these studies when compared to Hinkley et al.  may support the argument that adiposity is accumulated over a longer time period, and movement behaviours need a longer exposure period before effects can be observed . Additionally, studying adiposity cross-sectionally in preschool-aged children is difficult due to adiposity rebound , thus observed longitudinal associations could result from assessing adiposity at an age with more stability in this regard.
Only adiposity and growth indicators were examined in the previous guideline adherence and physical development studies [18, 34, 35], whereas the current study also included motor skills. Subsequently, in this sample meeting a combination of physical activity and sleep recommendations was associated with a 5 point higher object motor skills score and an 8 point higher total motor skills score. Therefore, motor skills along with expected adult height strongly contributed to the overall physical development finding. To better understand which aspects of physical development are most related to movement behaviour patterns, more studies examining guideline adherence that continue to use a broad array of physical development indicators are needed. Further, studies using longitudinal study designs are needed to examine any bidirectional associations between movement behaviours and development.
In this study, no significant associations were observed between guideline adherence and overall cognitive development, though the number of recommendations met was associated with higher response inhibition. McNeill et al.  also used the Early Years Toolbox  to measure cognitive development in children aged 3–5 years, followed up after one year. In agreement with the presented study, no significant associations were observed for guideline adherence at baseline and visual-spatial working memory at follow-up . However, in contrast with the present study, McNeill and colleagues (2020) found no significant associations for guideline adherence at baseline and response inhibition at follow-up. Further, McNeill et al.  did find that meeting the physical activity recommendation was associated with higher cognitive shifting one year later. Unfortunately, the current study did not measure cognitive shifting, thus comparisons are not possible. Beyond the Early Years Toolbox, Hinkley et al.  found that meeting sleep guidelines for children aged 3–5 was associated with higher scores for reading, writing, spelling, numeracy, and language domains of academic achievement at ages 8–9 years. This could speak to the importance of early movement behaviour patterns for cognitive achievements (e.g., grades, academic awards) and cognitive abilities that develop later in childhood, such as cognitive shifting . Future research should confirm longitudinal findings, while continuing to explore various cognitive achievement and ability assessments.
No significant associations were observed between guideline adherence and overall social-emotional development in this study, though meeting the sleep recommendations were associated with higher behavioural self-regulation. No studies could be found examining 24-h movement behaviour guideline adherence and behavioural self-regulation in early childhood, so comparisons are difficult. However, two longitudinal studies also found null associations for guideline adherence with behavioural and emotional problems (e.g., total problems, internalizing problems, externalizing problems) [18, 37]. This contrasts with a cross-sectional study of 3-year-old children that observed associations for meeting sedentary behaviour recommendations, and combinations including sedentary behaviour recommendations, with lower total problems, externalizing problems, and internalizing problems . Future studies should explore potential mechanisms for the differences in study findings. Beyond behavioural and emotional problems, Cliff et al.  found that meeting recommendations for sleep, and combinations including sleep, were favourably associated with theory of mind and emotional comprehension. To better understand the myriad of indicators making up social-emotional development, future research should examine a broad spectrum of indicators in relation to movement behaviours.
Previous studies examining 24-h movement guidelines and development in a similar age group as this study have reported adherence as 19–94% for physical activity, 84–98% for sleep, 17–63% for sedentary behaviour, and 3–20% for all three [18, 34, 35, 37, 39, 40]. In the current study 94% of participants met the physical activity guidelines, which is similar to other studies (89%-94%) that also measured physical activity with a hip-worn ActiGraph accelerometer and used the same physical activity cut-points [18, 37, 40]. However, 94% is seemingly high compared to 19% when using a wrist-worn ActiGraph accelerometer and larger epochs , 31% when different physical activity cut-points are applied to the ActiGraph , and 62% when using the Actical accelerometer . Additionally, in the current study participants had 43% adherence to all three guidelines, compared to the previous studies that showed 3–20% adherence [18, 34, 35, 37, 39, 40]. The sample examined in the current study may not be representative of the broader population based on their healthy movement behaviour patterns. In fact, two studies reported adherence to all three guideline recommendations as 3% in Canada  and 5% in Edmonton, Alberta . Differences in findings could indicate this sample has poor generalizability or could demonstrate the issues when comparing estimates using different movement behaviour measurements. Thus, achieving consensus on the measurement of movement behaviours, especially accelerometer protocols (e.g., accelerometer brand, wear-site, cut-points), will allow for comparisons across future studies. As well, future research could examine relative-intensity accelerometer cut-points to better represent an individuals intensity of physical activity based on their fitness .
Meeting sleep recommendations or combinations of recommendations that include sleep are frequently reported to be favourable for children’s development [18, 37, 39, 40], including the results presented in the current study. Interestingly, when using the same data, no significant associations were observed in a compositional analysis between sleep and development outcomes, relative to the other movement behaviours . Differences in results could exist since the previous study examined relationships linearly, whereas the current study examined guideline recommendation adherence based on a window of time. Some argue that the benefits of sleep for healthy development are not a linear relationship, instead benefits exist in a window of time (e.g., 10–13 h/day), or an inverted U shape . In other words, both too little and too much sleep could have detrimental effects on development. Interestingly, of the participants not meeting sleep recommendations in this sample, half were above, and half were below the recommendations. Therefore, findings in the current study support the rationale of choosing a window of time, instead of a threshold, when creating sleep recommendations in the 24-Hour Movement Guidelines in Canada [5, 9]. Heterogeneity in findings may also be explained by the differences in analyses, as compositional analyses consider one movement behaviour in relation to all other movement behaviours, while the current study only considered combinations of movement behaviours.
In addition to comparisons with sleep, linear regressions from our previous compositional analysis also found null associations between physical activity (i.e., LPA and MVPA) with cognitive and social-emotional development. However, favourable associations were found between MVPA and physical development . In contrast to the compositional findings, the current study did not find favourable associations between physical activity guideline adherence and physical development. It is important to note, 94% of this sample met the physical activity guidelines. Thus, in our sample the thresholds for physical activity guideline adherence are likely not sufficient to differentiate between those with higher MVPA and better physical development as seen in the previous compositional analyses. Further, our previous compositional analysis found favourable associations between accelerometer-measured stationary time and cognitive development . Compared to the current null findings for screen time, this could indicate that this sample was engaged in non-screen based sedentary behaviours that have previously demonstrated favourable associations with cognitive development. For instance, Poitras et al.  found that reading to early years children was favourably associated with cognitive development. Therefore, future research should continue measuring a range of types of sedentary behaviours (e.g., screen time, stationary time, reading time) to better understand the mechanisms of these associations.
To our knowledge, no other studies examining 24-h movement behaviours have created composite scores to represent physical, cognitive, social-emotional, and overall development. This approach can be beneficial from a public health messaging perspective, since the use of these broader domains of development creates a more succinct finding, and subsequently more succinct messaging. Further, combining scores could be protective of acute performance issues on any one task (e.g., loss of attention) or questionnaire item (e.g., parent misunderstood). However, there are also limitations with creating a composite score. For instance, one outcome (e.g., motor skills) could be overly influential and thus over representative of physical development. The technique used in this study created equal weights for each outcome domain (i.e., physical, cognitive, and social-emotional), so the overall development composite score was equally represented by the three development domains. Differential weighting could have also been explored, such as regression weights and expert consensus weighting (e.g., important = multiply scores by 2, less important = multiply scores by 1) . Future studies could compare different techniques for creating an overall development score, such as identifying a criterion measure for regression weighting and weighting based on an expert consensus process.
The main strength of this study was the inclusion of a variety of development outcomes, across the domains of physical, cognitive, and social-emotional development. Though the variety of developmental indicators measured could make replication difficult. Ideally, a future synthesis of the literature could help identify universal core measures to be included when assessing development, similar to efforts underway in the SUNRISE study . Further, this study used device-based measures of physical activity and sleep, and the total screen time measure included screen viewing and video game playing on a variety of mediums (e.g., tablet, cell phones, television), instead of only the traditional television viewing. The study also had some limitations. For instance, the cross-sectional study design prevents causation from being inferred. Additionally, the small convenience sample was recruited from a sports-based program and may not be generalizable to the broader population. Though a previous review has suggested that > 2 accelerometer wear days (regardless of weekend or weekday) is sufficient in this age group , that was based on waking day wear protocols. Thus, the use of > 2 days could lack reliability in this sample since a waking wear day protocol was not used, and future research is needed to re-examine minimum wear time and valid days needed for reliable 24-h wear protocols. The low reliability scores in this sample for externalizing and prosocial behaviours may have limited the ability to detect significant associations for the social-emotional development composite score. Lastly, the multiple comparisons in our analyses may have increased the risk for Type I error.