WHO European Childhood Obesity Surveillance Initiative: associations between sleep duration, screen time and food consumption frequencies

Brnhorst et al. BMC Public Health WHO European Childhood Obesity Surveillance Initiative: associations between sleep duration, screen time and food consumption frequencies Background: Both sleep duration and screen time have been suggested to affect children's diet, although in different directions and presumably through different pathways. The present cross-sectional study aimed to simultaneously investigate the associations between sleep duration, screen time and food consumption frequencies in children. Methods: The analysis was based on 10 453 children aged 6-9 years from five European countries that participated in the World Health Organization European Childhood Obesity Surveillance Initiative. Logistic multilevel models were used to assess associations of parent-reported screen time as well as sleep duration (exposure variables) with consumption frequencies of 16 food items (outcome variables). All models were adjusted for age, sex, outdoor play time, maximum educational level of parents and sleep duration or screen time, depending on the exposure under investigation. Results: One additional hour of screen time was associated with increased consumption frequencies of 'soft drinks containing sugar' (1.28 [1.19;1.39]; odds ratio and 99% confidence interval), 'diet/light soft drinks' (1.21 [1.14;1.29]), 'flavoured milk' (1.18 [1.08;1.28]), 'candy bars or chocolate' (1.31 [1.22;1.40]), 'biscuits, cakes, doughnuts or pies' (1.22 [1.14;1.30]), 'potato chips (crisps), corn chips, popcorn or peanuts' (1.32 [1.20;1.45]), 'pizza, French fries (chips), hamburgers'(1.30 [1.18;1.43]) and with a reduced consumption frequency of 'vegetables (excluding potatoes)' (0.89 [0.83;0.95]) and 'fresh fruits' (0.91 [0.86;0.97]). Conversely, one additional hour of sleep duration was found to be associated with increased consumption frequencies of 'fresh fruits' (1.11 [1.04;1.18]) and 'vegetables (excluding potatoes)' (1.14 [1.07;1.23]). Conclusion: The results suggest a potential relation between high screen time exposure and increased consumption frequencies of foods high in fat, free sugar or salt whereas long sleep duration may favourably be related to children's food choices. Both screen time and sleep duration are modifiable behaviours that may be tackled in childhood obesity prevention efforts. Sleep; Screen time; Food frequency; TV viewing; Computer use; Childhood overweight; Cross-sectional study; Snacks; Europe - Background The rising prevalence of overweight and obesity in children during the last decades is alarming. Childhood obesity is likely to track into adulthood and may result in metabolic, musculoskeletal or cardiovascular diseases and increase cancer risk [1-3]. One main factor suggested for the emerging obesity epidemic relates to the changes in lifestyles. Today children may spend more time with electronic media than with any single activity other than sleeping [4]. Often televisions (TV), personal computers (PC), smart phones or game consoles are used concurrently all of which encourage sedentary behaviour. In addition, the availability of electronic media in childrens bedrooms has increased dramatically, which was found to be a significant determinant of total screen time [5]. In this context, positive associations between having a TV in a childs bedroom and overweight/ obesity were also reported [6]. To date, the pathway of the effect of screen time on overweight/obesity is not completely understood. The displacement of more active pursuits by spending time with electronic media has been suggested to lead to obesity, but this hypothesis is not fully supported by research evidence [7-9]. Screen time may further affect weight status through its impact on energy intake [10-12]. As a potential direct mechanism, Bellissimo et al. suggested TV viewing while eating to alter energy intake by delaying satiation and reducing satiety signals from previously consumed foods [11]. Another discussed pathway refers to the exposure to advertising of foods high in saturated fats, trans-fatty acids, free sugars or salt, which may increase childrens requests for those products [13]. Early socialization of children to associate TV time with snacking of unhealthy foods exemplified through parents may further explain the association of TV time with excess energy intake [14]. Consequently, screen time may operate through its effect on energy intake in addition to the displacement of high-energy-expending activities by sedentary activities [10,15]. Moreover, TV viewing and PC use were both shown to be associated with shorter sleep duration [5]. In a systematic review of world literature, consistent rapid declines in the sleep duration of children and adolescents over the last 100 years have been reported [16], which may partially be attributed to increases in total screen time. Short sleep duration is another known risk factor for obesity [17,18]. Also the exact mechanism through which sleep duration affects overweight/obesity is not yet clear. Apart from behavioural hypotheses like the less sleep more time to eat one [19,20], several endocrinological mechanisms have been discussed to explain this association including pathways via insulin, cortisol, ghrelin and leptin [21]. For example, the appetite-lowering hormone leptin was reported to be less secreted in periods of short sleep duration whereas ghrelin, an appetitestimulating hormone, was shown to be elevated. These sleep-induced hormonal changes may lead to alterations in appetite, hunger and food consumption and may hence promote overweight/obesity through its effect on diet [22-25]. Summing up, screen time and sleep duration seem to be interrelated and both have been suggested to affect childrens eating behaviours, although in different directions and presumably through different pathways [26,27]. Therefore, the present study aims to simultaneously investigate the effects of screen time and sleep duration on childrens food consumptions. Both of these exposures are modifiable behaviours, and thus the results may be of public health interest, in particular for policy-makers as they may provide insights to prevent the excessive weight gain particularly in young children. Methods World Health Organization European Childhood Obesity Surveillance Initiative In 2006, the World Health Organization (WHO) Regional Office for Europe initiated with 13 Member States the WHO European Childhood Obesity Surveillance Initiative (COSI). These 13 countries were: Belgium (Flemish region only), Bulgaria, Cyprus, Czech Republic, Ireland, Italy, Latvia, Lithuania, Malta, Norway, Portugal, Slovenia and Sweden. COSI aims to measure trends in overweight and obesity in children aged 6.09.9 years, in order to monitor the progress of the epidemic and to permit intercountry comparisons. The first COSI data collection round took place from September 2007 to December 2008. The actual measurement period within this data collection round, however, coul (...truncated)