Table 6 Summary of research needs to address gaps in relation to the development of 24-h integrated movement guidelines for the early years

General

 • Timing and consistency studies needed for sedentary behaviour, physical activity and sleep

Physical activity

 • More accurate ways of objectively measuring physical activity are needed (currently no valid and reliable accelerometer cut points for infants).

 • More research needed to determine how MVPA is defined for young children, given the sporadic nature of their activity.

 • More evidence on the associations between light-intensity physical activity and health and development outcomes is needed and how light-intensity physical activity is defined.

 • Better evidence needed for “a variety of ways” (for infant guidelines).

 • More evidence needed overall for infants.

Sedentary behaviour

 • No evidence was “high quality” (only 2 RCTs and several limitations across studies).

 • Only one longitudinal study used objective measures of sedentary behaviour (e.g., accelerometers).

 • No studies examined newer/evolving technologies that contribute to sedentary time (e.g., tablets, FaceTime/Skype, small screens); only 1 study examined mobile phone use.

 • Few studies examined certain sedentary behaviour exposures (e.g., sitting, supine position, reading, internet, sedentary quiet play).

 • Difficult to define and measure “sedentary behaviour” in infants given the child/adult concept of “breaking up sedentary behaviour” may not be relevant to non-walking infants.

Sleep

The review only focused on sleep duration

 • Many other important factors beyond sleep duration should be considered in the development of sleep recommendations, including aspects of sleep quality such as sleep efficiency (i.e., proportion of the sleep opportunity spent in sleep), timing (i.e., bedtime/wake-up time and naps), sleep architecture (i.e., the number of different sleep stages and composition of sleep in general), consistency (i.e., day-to-day variability, seasonal changes), and sleep consolidation (i.e, organization of sleep across the night, amount of waking after sleep onset, etc)

 • In addition, sleep duration in the early years is generally comprised of both daytime and night time sleep. However, it has been reported that the effects of daytime sleep on health may not be the same as night time sleep, with positive effects of sleep duration suggested to relate to the stage in sleep transition from polyphasic to monophasic sleep during which naps cease Multiple age groups (e.g., toddlers, preschoolers) were also grouped together, despite obvious differences in development

 • Development progresses rapidly during the early years and many factors could have confounded the associations that have been reported (e.g., growth, eating habits, environment, locomotion, etc.)

 • Ideally, future research should use narrower age groups that are aligned with the current sleep duration recommendations (e.g., newborns [0–3 months], infants [4–11 months], toddlers [1–2 y], preschoolers [3–5 y])

The available evidence relies heavily on cross-sectional studies that use parent-reported sleep durations

 • Subjective sleep reports are less reliable than objective measures of sleep. It is also well-known that parent-reported sleep duration overestimates actual sleep duration compared with objective measures.

 • Subjective sleep reports are therefore valid for screening, but are less consistent and reliable in estimating sleep pattern variables such as sleep duration, night wakings, and sleep onset latency (Bauer and Blunden, 2008).

 • Even when objective measurements are used, there is a wide variety of largely incommensurable metrics for duration, efficiency and fragmentation of sleep. Where possible, future research should include objective measures of sleep, with agreed metrics. Additionally, where only subjective measures are included the questions used to evaluate sleep should be carefully selected as this can greatly impact the validity of self-report