Temporal and bi-directional associations between sleep duration and physical activity/sedentary time in children: An international comparison

Highlights

• The association between nocturnal sleep and daytime activity was assessed.

• Longer sleep predicted more physical activity (PA) and less sedentary time (SED).

• More moderate-to-vigorous-intensity PA and less SED predicted longer sleep.

• Child's sex and study sites modified the bi-directional associations.

• The clinical relevance of the statistically significant findings may be debated.

Abstract

The purpose of this multinational and cross-sectional study was to investigate whether nighttime sleep duration was associated with physical activity (PA) and sedentary time (SED) the following day, whether daytime PA/SED were associated with sleep duration the subsequent night, and whether the associations were modified by sex and study sites. Data from 5779 children aged 9–11 years were analyzed. A waist-worn Actigraph GT3X + accelerometer was used to assess children's 24-h movement behaviours for 7 days, i.e. sleep duration, total SED, light-intensity physical activity (LPA), and moderate- to vigorous-intensity physical activity (MVPA). Multilevel linear regression models were used to account for the repeated measures nested within participants (there were up to 7 sleep → PA/SED and PA/SED → sleep pairings per participant) and schools, and adjusted for covariates. To facilitate interpretation, all sleep and PA/SED variables were standardized. Results showed that the relationship between sleep and PA/SED is bi-directional in this international sample of children. Specifically, for each one standard deviation (SD) unit increase in sleep duration, SED the following day decreased by 0.04 SD units, while LPA and MVPA increased by 0.04 and 0.02 SD units, respectively. Sleep duration decreased by 0.02 SD units and increased by 0.04 SD units for each one SD unit increase in SED and MVPA, respectively. Sleep duration was not affected by changes in LPA. These associations differed across sex and study sites in both directions. However, since the observed effect sizes are subtle, public health initiatives should consider the clinical and practical relevance of these findings.

Introduction

Recently, the Canadian 24-Hour Movement Guidelines for Children and Youth provided evidence-informed recommendations for a healthy day, comprising an integration of sleep, physical activity (PA) and sedentary time (SED) (Tremblay et al., 2016). For instance, longer sleep duration is associated with an array of positive health outcomes among school-aged children, such as lower adiposity indicators, better emotional regulation, academic achievement and quality of life/well-being (Chaput et al., 2016). Sufficient PA, including light-intensity physical activity (LPA) and moderate- to vigorous-intensity physical activity (MVPA), is also associated with better mental and physical health outcomes (Janssen and LeBlanc, 2010, Biddle and Asare, 2011, Kwon et al., 2011); while excess SED is associated with unfavorable health indicators (Biddle and Asare, 2011, Carson et al., 2016). However, in recent decades, there has been declines in sleep duration and PA levels, and increases in SED among children worldwide (Matricciani et al., 2012, Dollman et al., 2005, Hallal et al., 2012).

There is a growing interest to determine whether there is a virtuous/vicious cycle between children's nighttime sleep duration and daytime PA/SED in the context of the 24-hour lifestyle recommendations. Thus far, research examining the possible bi-directional connection between sleep duration and PA/SED within the pediatric population has produced inconsistent findings. Studies have reported that nighttime sleep duration positively (Hart et al., 2016), negatively (Sorić et al., 2015, Pesonen et al., 2011), or did not (Ekstedt et al., 2013, Vincent et al., 2017) predict the next day's PA. Similarly, studies have reported that PA/SED during the day positively (Nixon et al., 2008), negatively (Pesonen et al., 2011), or did not (Ekstedt et al., 2013, Vincent et al., 2017, Nixon et al., 2008, Dworak et al., 2008) predict the subsequent night's sleep duration. Reasons for these inconsistency remain unclear. Also, research surrounding the association between sleep duration and SED is limited to only one study (Nixon et al., 2008). More epidemiological inquiry is clearly needed based on the available equivocal evidence.

Furthermore, existing research has been mainly conducted in developed countries (Sorić et al., 2015, Pesonen et al., 2011, Ekstedt et al., 2013, Vincent et al., 2017, Nixon et al., 2008, Nixon et al., 2009), with only one study from a developing country (Sorić et al., 2015). The role of higher-order environmental correlates of children's daily lifestyle behaviours are not well understood due to the limited socio-cultural variability. The present multinational study is unique in its international diversity and provides an opportunity to determine whether the relationships of interest differ across countries and socio-cultural settings. Such information is key to informing the development of interventions that can be culturally adapted for implementation around the world.

The objective of this study was to examine the temporal and bi-directional associations between sleep duration and PA/SED in children from 12 countries representing a wide range of geographic and social contexts. Specifically, this study examined whether sleep duration the preceding night was associated with total SED/LPA/MVPA accumulated the following day, and whether SED/LPA/MVPA during the day were associated with sleep duration the subsequent night. We hypothesized that longer sleep duration would be temporally and bi-directionally associated with less SED and more LPA/MVPA. Based on the available evidence, we also hypothesized that the associations of interest would differ across sex (Sorić et al., 2015, Pesonen et al., 2011) and study sites (Sorić et al., 2015, Pesonen et al., 2011, Vincent et al., 2017).