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BackgroundPhysical activity and sedentary behaviour among children should be measured accurately in order to investigate their relationship with health. Accelerometry provides objective and accurate measurement of body movement, which can be converted to meaningful behavioural outcomes. The aim of this study was to evaluate the best evidence for the decisions on data collection and data processing with accelerometers among children resulting in a standardized protocol for use in the participating countries.Methods/DesignThis cross-sectional accelerometer study was conducted as part of the European ENERGY-project that aimed to produce an obesity prevention intervention among schoolchildren. Five countries, namely Belgium, Greece, Hungary, Switzerland and the Netherlands participated in the accelerometer study. We used three different Actigraph models-Actitrainers (triaxial), GT3Xs and GT1Ms. Children wore the device for six consecutive days including two weekend days. We selected an epoch length of 15 seconds. Accelerometers were placed at children's waist at the right side of the body in an elastic belt.In total, 1082 children participated in the study (mean age = 11.7 ± 0.75 y, 51% girls). Non-wearing time was calculated as periods of more than 20 minutes of consecutive zero counts. The minimum daily wearing time was set to 10 hours for weekdays and 8 hours for weekend days. The inclusion criterion for further analysis was having at least three valid weekdays and one valid weekend day. We selected a cut-point (count per minute (cpm)) of <100 cpm for sedentary behaviour, <3000 cpm for light, <5200 cpm for moderate, and >5200 cpm for vigorous physical activity. We also created time filters for school-time during data cleaning in order to explore school-time physical activity and sedentary behaviour patterns in particular.DiscussionThis paper describes the decisions for data collection and processing. Use of standardized protocols would ease future use of accelerometry and the comparability of results between studies.

Research on associations of positive mental health, in contrast to mental ill‐health, with sleep duration and sleep disturbances in young populations is scarce. In particular, longitudinal studies focussing on the influence of positive mental health on sleep characteristics are lacking. Therefore, we investigated cross‐sectional and longitudinal associations of psychosocial well‐being with sleep duration and sleep disturbances. For the cross‐sectional analysis, we used data of 3‐15‐year‐old children and adolescents participating in the 2013/14 examination of the European IDEFICS/I.Family cohort study (N = 6,336). The longitudinal analysis was restricted to children who also participated in the 2009/10 examination (N = 3,379). Associations between a psychosocial well‐being score created from 16 items of the KINDLR Health‐Related Quality of Life Questionnaire covering emotional well‐being, self‐esteem and social relationships, an age‐standardized nocturnal sleep duration z‐score and two sleep disturbance indicators (“trouble getting up in the morning”, “difficulties falling asleep”) were estimated using linear and logistic mixed‐effects models. Cross‐sectionally, a higher well‐being score was associated with longer sleep duration and lower odds of sleep disturbances. A positive change in the well‐being score over the 4‐year period was associated with longer sleep duration and lower odds of sleep disturbances at follow‐up. However, there was only weak evidence that higher psychosocial well‐being at baseline was associated with better sleep 4 years later. Thus, our results suggest that increases in well‐being are associated with improvements in both sleep duration and sleep disturbances, but that well‐being measured at one point in time does not predict sleep characteristics several years later.

¶ Membership of the IDEFICS and I.Family Consortia is listed in the Acknowledgments.

Food intake among European children varied with different levels of daily MVPA. Low time spent in MVPA was associated with lowest consumption of both high- and low-energy-dense foods and high fast-food consumption.