Objectives. We examined changes in sleep-onset difficulties over time, and associations with physical activity and screen time behavior among adolescents.Methods. We used data from last four survey waves of the Health Behavior of School-aged Children (HBSC) study (2002-2006-2010-2014). Multilevel logistic regression analyses were conducted to explore associations between regular sleeping difficulties, excessive screen time exposure, and being insufficiently physically active (i.e. < 60 min daily) among 33 European and non-European countries. Results.Findings indicate an increase in the prevalence of sleep-onset difficulties and in excessive screen time exposure, and a small but significant increase in physical activity levels. Additionally, adolescents exceeding 2h daily screen time had 20% higher odds of reporting sleep-onset difficulties, while no association was found for physical activity. The strength of the association between screen time and sleep-onset difficulties increased over time, which may reflect a change in type of screen time use (e.g. the increased use of easy accessible screens such as smartphones and tablets). Conclusions. Effective strategies to reduce screen time are key to reverse the detrimental trend in sleeponset difficulties among adolescents.Trends in sleeping difficulties among European adolescents: are these associated with physical inactivity and excessive screen time?

This study examines the mediating role of sleep duration and sleep onset difficulties in the association of school pressure, physical activity, and screen time with psychological symptoms in early adolescents. Data were retrieved from 49,403 children (13.7 ± 1.6 years old, 48.1% boys) from 12 countries participating in the World Health Organization (WHO) “Health Behaviour in School-aged Children” 2013/2014 study. A validated self-report questionnaire assessed psychological symptoms (feeling low, irritability or bad temper, feeling nervous), school pressure, physical activity (number of days/week 60 min moderate-to-vigorous), screen time, sleep duration on week- and weekend days, and perceived difficulties in getting asleep. Multilevel mediation analyses were conducted. School pressure and screen time were positively associated with psychological symptoms, whereas physical activity was negatively associated. With the exception of sleep duration in the association between physical activity and psychological symptoms, all associations were significantly mediated by sleep duration on week- and weekend days and sleep onset difficulties. Percentages mediated ranged from 0.66% to 34.13%. This study partly explains how school pressure, physical activity, and screen time are related to adolescents’ psychological symptoms. Future interventions improving adolescents’ mental well-being could target schoolwork, physical activity, and screen time, as these behaviours are directly and indirectly (through sleep) related to psychological symptoms.

Background Wearable trackers for monitoring physical activity (PA) and total sleep time (TST) are increasingly popular. These devices are used not only by consumers to monitor their behavior but also by researchers to track the behavior of large samples and by health professionals to implement interventions aimed at health promotion and to remotely monitor patients. However, high costs and accuracy concerns may be barriers to widespread adoption. Objective This study aimed to investigate the concurrent validity of 6 low-cost activity trackers for measuring steps, moderate-to-vigorous physical activity (MVPA), and TST: Geonaut On Coach, iWown i5 Plus, MyKronoz ZeFit4, Nokia GO, VeryFit 2.0, and Xiaomi MiBand 2. Methods A free-living protocol was used in which 20 adults engaged in their usual daily activities and sleep. For 3 days and 3 nights, they simultaneously wore a low-cost tracker and a high-cost tracker (Fitbit Charge HR) on the nondominant wrist. Participants wore an ActiGraph GT3X+ accelerometer on the hip at daytime and a BodyMedia SenseWear device on the nondominant upper arm at nighttime. Validity was assessed by comparing each tracker with the ActiGraph GT3X+ and BodyMedia SenseWear using mean absolute percentage error scores, correlations, and Bland-Altman plots in IBM SPSS 24.0. Results Large variations were shown between trackers. Low-cost trackers showed moderate-to-strong correlations (Spearman r=0.53-0.91) and low-to-good agreement (intraclass correlation coefficient [ICC]=0.51-0.90) for measuring steps. Weak-to-moderate correlations (Spearman r=0.24-0.56) and low agreement (ICC=0.18-0.56) were shown for measuring MVPA. For measuring TST, the low-cost trackers showed weak-to-strong correlations (Spearman r=0.04-0.73) and low agreement (ICC=0.05-0.52). The Bland-Altman plot revealed a variation between overcounting and undercounting for measuring steps, MVPA, and TST, depending on the used low-cost tracker. None of the trackers, including Fitbit (a high-cost tracker), showed high validity to measure MVPA. Conclusions This study was the first to examine the concurrent validity of low-cost trackers. Validity was strongest for the measurement of steps; there was evidence of validity for measurement of sleep in some trackers, and validity for measurement of MVPA time was weak throughout all devices. Validity ranged between devices, with Xiaomi having the highest validity for measurement of steps and VeryFit performing relatively strong across both sleep and steps domains. Low-cost trackers hold promise for monitoring and measurement of movement and sleep behaviors, both for consumers and researchers.

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Samenvatting Achtergrond. Omdat het slaapgedrag van adolescenten in de afgelopen decennia verslechterd is en dit samenhangt met negatieve gezondheidsgevolgen, zijn interventies nodig. Voor de ontwikkeling daarvan is kennis nodig over de belangrijkste factoren die het slaapgedrag beïnvloeden. Het doel van dit kwalitatieve onderzoek was de determinanten van slaapgedrag bij Vlaamse adolescenten te onderzoeken. Methode. Er werden negen focusgroepgesprekken met telkens acht adolescenten georganiseerd (63,9 % meisjes, 14,8 ± 1,0 jaar) met behulp van een gestandaardiseerde vragenroute. Op de transcripties van de focusgroepgesprekken werd een thematische inhoudsanalyse uitgevoerd met Nvivo 11. Resultaten. Adolescenten hadden voldoende kennis van de kortetermijngevolgen van slaaptekort, maar beperkte kennis van slaaprichtlijnen, slaaphygiëne en