Physical activity is widely promoted as an effective method to improve sleep quality [∗[1], [2], [3], [4], [5], [6]]. Recent meta-analyses offer support for this premise, with positive associations between physical activity and sleep found in adolescents and young adults (e.g., effect size between objectively measured physical activity and objectively measured sleep; d = 1.02, 95% CI = 0.16 to 2.20) [7] and in adults (e.g., effect size between regular exercise and total sleep time; d = 0.25, 95% CI = 0.07 to 0.43) [8]. However, the evidence among children is unclear with inconsistent findings among empirical studies and no meta-analytical review conducted to date [9].
International guidelines recommend that children 3–5 years of age obtain between 10 and 13 h of sleep per night and that children 6–13 years of age sleep between 9 and 11 h per night [10]. However, there is evidence that young people worldwide tend to sleep less than these recommended levels [[11], ∗[12], [13]]. For example, in their examination across 12 different countries, Roman-Vinas et al. [14], reported only 42% of children met this recommendation. Moreover, 20–30% of children experience paediatric sleep problems (e.g., bedtime problems, night awakenings, etc.) [15]. These sleep deficits are concerning because adequate sleep is important for children's growth, maturation and development [16].
Buysse proposed five components of sleep that are important when considering sleep health: duration, efficiency, timing, subjective quality, and daytime tiredness [17]. Shortened sleep duration, poor sleep efficiency, and erratic sleep timing are associated with impaired concentration and poorer academic performance [18], information retention, and working memory [19,20]. Short sleep duration and poor sleep quality are also linked to affective disorders, such as depression, anxiety and attention deficit disorder [21,22]. Furthermore, short sleep duration, daytime tiredness, and poor sleep quality in children are linked with an increased risk of injuries and accidents [23], alcohol and drug use later in adolescence [24], and obesity [25,26].
Physical activity is widely promoted for its many health benefits for people of all ages [27,28]. International physical activity guidelines for children aged 5–17 years recommend at least 60 min of at least moderate-intensity physical activity per day [29]. In a systematic review of children and adolescents aged 5–17 years, Janssen and Leblanc reported that physical activity positively influences bone health, cholesterol, blood pressure, weight management, obesity, and metabolic syndrome [30]. Physical activity also benefits children's mental health, showing positive associations on depression and anxiety [31].
Physical activity and sleep are individually important for health; however, it is also important to understand how these behaviours interact [[32], [33], [34], [35]]. Lang et al. [7] demonstrated that both subjective ratings and objective recording of time spent being physically active had a positive impact on subjective ratings and objective recording of time spent sleeping in adolescents and young adults, with objective measurements showing the strongest effects. In adults, Kredlow et al. [8] have also shown positive effects from acute and regular exercise on a variety of sleep outcomes including sleep duration, sleep efficiency, and sleep quality. In their meta-analysis, Kredlow et al. [8] also show that effects were moderated by gender, age, baseline fitness level, and a variety of exercise characteristics. However, both these meta-analyses have focused on the effect of physical activity or exercise on sleep and not the other direction. Additionally, no meta-analysis examining the relationship between physical activity and sleep has included children under 13-years-old [∗[1], [2], [3], [4], [5], [6]]. Thus, the efficacy of physical activity as a method to improve sleep in children is unknown. It is also unknown if the association between physical activity and sleep is bidirectional [36]. Indeed, some evidence suggests that poor sleep may decrease the amount of physical activity that children accumulate [37]. As this association between physical activity and sleep in children is unclear, a meta-analysis of the existing literature is needed for this age group [9,38,39].
Our objectives in this systematic review were to 1) investigate the associations between physical activity and sleep behaviour among healthy children, 2) if these associations exist, examine evidence regarding direction of the associations, and 3) identify potential moderators in the associations between physical activity and sleep. Based on findings from meta-analyses involving adolescents and adults [7,8], we hypothesized that there would be 1) a positive association between physical activity and sleep in healthy children, 2) that the associations would be stronger for males, for older children, for children who are regularly physically active, and for children with regular sleep patterns, and 3) that stronger associations would be found between objectively measured effects than subjectively measured effects. We also investigated whether the relationship between physical activity and sleep in children is bidirectional.
We prospectively registered this review with the International Prospective Register of Ongoing Systematic Reviews (PROSPERO ID: CRD42017057217) and report our findings according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [40].
We included articles if they: 1) reported results from a sample of 3–13-year-old children (i.e., the study reported a sample mean age between 2.50 and 13.49 years); 2) employed a cross-sectional, longitudinal, or
We identified 29,720 records, of which Covidence removed 13,514 duplicates. After screening titles and abstracts, we removed a further 15,820 records. We considered the full-text version of the remaining 386 records against our inclusion criteria. At the final stage, we included 47 studies in the meta-analysis (see Fig. 1) [9,38,39,[59], [60], [61], [62], [63], [64], [65], [66], [67], [68], [69], [70], [71], [72], [73], [74], [75], [76], [77], [78], [79], [80], [81], [82], [83], [84], [85], [86]
To our knowledge, this is the first meta-analysis to investigate the association between physical activity and sleep in healthy children. We quantitatively examined several different physical activity and sleep outcomes in an overall multilevel meta-analytical model and in individual outcome category meta-analyses. In addition, we investigated whether the findings were moderated by gender, age, direction of association, study design, risk of bias, study quality, year of publication, or
Our aim was to meta-analyse the current literature on physical activity and sleep in healthy children. We found little evidence of an association overall with some weak positive associations between vigorous physical activity and sleep. While further investigation into moderators yielded some significant associations for age and the direction of association, these associations were also weak and were found only within specific categories of the data. Due to high heterogeneity in our models,
DA, CL, TS, PP, and MD conceived and designed the study. DA performed all searches. DA, JL, TH, and RH screened included studies and extracted the data. DA drafted the first version of the manuscript. DA, TS, CL, MD, BdPC, and PP contributed to subsequent versions of the manuscript. TS, CL, BdPC, and PP gave advice in performing analyses and interpreting the results. All authors contributed critically to subsequent revisions and approved the final manuscript. DA attests that all listed authors
MJD has received research grants from National Health and Medical Research Council during the conduct of the study. Our study suggests that there is little association between physical activity and sleep behaviour in children. Some evidence suggests that vigorous physical activity may have a positive influence on sleep, specifically sleep duration. However, the current findings are weak. Few longitudinal and experimental studies have examined children's physical activity and sleepPractice points
The authors do not have any conflicts of interest to disclose.
We thank the library staff at Australian Catholic University for the assistance with developing the database search strategy.
The most important references are denoted by an asterisk.
