Geneviève Leduc

Identifying children's nocturnal sleep using 24-h waist accelerometry.

PURPOSE The purposes of this study were 1) to add layers and features to a previously published fully automated algorithm designed to identify childrens nocturnal sleep and to exclude episodes of nighttime nonwear/wakefulness and potentially misclassified daytime sleep episodes and 2) to validate this refined sleep algorithm (RSA) against sleep logs. METHODS Forty-five fourth-grade school children (51% female) participants were asked to log evening bedtime and morning wake time and wear an ActiGraph GT3X+ (ActiGraph LLC, Pensacola, FL) accelerometer at their waist for seven consecutive days. Accelerometers were distributed through a single school participating in the Baton Rouge, USA, site of the International Study of Childhood Obesity, Lifestyle, and the Environment. We compared log-based variables of sleep period time (SPT), bedtime, and wake time to corresponding accelerometer-determined variables of total sleep episode time, sleep onset, and sleep offset estimated with the RSA. In addition, SPT and sleep onset estimated using standard procedures combining sleep logs and accelerometry (Log + Accel) were compared to the RSA-derived values. RESULTS RSA total sleep episode time (540 ± 36 min) was significantly different from Log SPT (560 ± 24 min), P = 0.003, but not different from Log + Accel SPT (549 ± 24 min), P = 0.15. Significant and moderately high correlations were apparent between RSA-determined variables and those using the other methods (r = 0.61 to 0.74). There were no differences between RSA and Log + Accel estimates of sleep onset (P = 0.15) or RSA sleep offset and log wake time (P = 0.16). CONCLUSIONS The RSA is a refinement of our previous algorithm, allowing researchers who use a 24-h waist-worn accelerometry protocol to distinguish childrens nocturnal sleep (including night time wake episodes) from daytime activities.

Independent and combined associations of total sedentary time and television viewing time with food intake patterns of 9- to 11-year-old Canadian children

The relationships among sedentary time, television viewing time, and dietary patterns in children are not fully understood. The aim of this paper was to determine which of self-reported television viewing time or objectively measured sedentary time is a better correlate of the frequency of consumption of healthy and unhealthy foods. A cross-sectional study was conducted of 9- to 11-year-old children (n = 523; 57.1% female) from Ottawa, Ontario, Canada. Accelerometers were used to determine total sedentary time, and questionnaires were used to determine the number of hours of television watching and the frequency of consumption of foods per week. Television viewing was negatively associated with the frequency of consumption of fruits, vegetables, and green vegetables, and positively associated with the frequency of consumption of sweets, soft drinks, diet soft drinks, pastries, potato chips, French fries, fruit juices, ice cream, fried foods, and fast food. Except for diet soft drinks and fruit juices, these associations were independent of covariates, including sedentary time. Total sedentary time was negatively associated with the frequency of consumption of sports drinks, independent of covariates, including television viewing. In combined sedentary time and television viewing analyses, children watching >2 h of television per day consumed several unhealthy food items more frequently than did children watching ≤2 h of television, regardless of sedentary time. In conclusion, this paper provides evidence to suggest that television viewing time is more strongly associated with unhealthy dietary patterns than is total sedentary time. Future research should focus on reducing television viewing time, as a means of improving dietary patterns and potentially reducing childhood obesity.

Correlates of objectively measured sedentary time and self-reported screen time in Canadian children

BackgroundDemographic, family, and home characteristics play an important role in determining childhood sedentary behaviour. The objective of this paper was to identify correlates of total sedentary time (SED) and correlates of self-reported screen time (ST) in Canadian children.MethodsChild- and parent-reported household, socio-demographic, behavioural, and diet related data were collected; directly measured anthropometric and accelerometer data were also collected for each child. Participants with complete demographic, anthropometric, and either SED (n=524, 41% boys) or ST (n=567, 42% boys) data from the Canadian site of the International Study of Childhood Obesity Lifestyle and the Environment (ISCOLE) were included in analysis. Sixteen potential correlates of SED and ST were examined using multilevel general linear models, adjusting for sex, ethnicity, number of siblings, and socio-economic status. All explanatory variables moderately associated (p<0.10) with SED and/or ST in univariate analyses were included in the final, fully-adjusted models. Variables that remained significant in the final models (p<0.05) were considered correlates of SED and/or ST.ResultsChildren averaged 8.5hours of daily SED; no differences in total SED, or total ST were seen between girls and boys, but boys reported significantly more video game/computer usage than girls. Boys also had higher waist circumference and BMI z-scores than girls. In the final models, waist circumference and number of TVs in the home were the only common correlates of both SED and ST. SED was also negatively associated with sleep duration. ST was also positively associated with mother’s weight status, father’s education, and unhealthy eating pattern score and negatively associated with healthy eating pattern score, and weekend breakfast consumption. Few common correlates existed between boys and girls.ConclusionSeveral factors were identified as correlates of SED and/or of ST in Canadian children; however, few correlates were common for both SED and ST, and for both boys and girls. This suggests that a single strategy to reduce SED and ST is unlikely to be effective. Future work should examine a variety of other, non-screen based sedentary behaviours and their potential correlates in the hopes of creating tailored public health messages to reduce SED and ST in both boys, and girls.

Objectively-measured sleep and its association with adiposity and physical activity in a sample of Canadian children

Cross‐sectional associations between objectively‐measured sleep duration, sleep efficiency and sleep timing with adiposity and physical activity were examined in a cohort of 567 children from Ottawa, Canada. Five‐hundred and fifteen children (58.8% female; age: 10.0 ± 0.4 years) had valid sleep measurements and were included in the present analyses. Physical activity, sedentary time and sleep parameters were assessed over 7 days (actigraphy). Height, weight and waist circumference were measured according to standardized procedures. Percentage body fat was assessed using bioelectric impedance analysis. Light physical activity and sedentary time were greater in children with the shortest sleep durations (P < 0.0001), whereas children with the highest sleep efficiencies had lower light physical activity and more sedentary time across tertiles (P < 0.0001). In multivariable linear regression analyses, and after adjusting for a number of covariates, sleep efficiency was inversely related to all adiposity indices (P < 0.05). However, sleep duration and sleep timing were not associated with adiposity indices after controlling for covariates. Inverse associations were noted between sleep duration and light physical activity and sedentary time (P < 0.0001). Sleep efficiency (P < 0.0001), wake time and sleep timing midpoint (P < 0.05) were negatively associated with light physical activity, but positively associated with sedentary time. In conclusion, only sleep efficiency was independently correlated with adiposity in this sample of children. Participants with the shortest sleep durations or highest sleep efficiencies had greater sedentary time. More research is needed to develop better sleep recommendations in children that are based on objective measures of sleep duration, sleep efficiency and sleep timing alike.

Electronic screens in children's bedrooms and adiposity, physical activity and sleep: do the number and type of electronic devices matter?

OBJECTIVE: To examine whether the number and type of electronic screens available in children’s bedrooms matter in their relationship to adiposity, physical activity and sleep.METHODS: A cross-sectional study was conducted involving 502 children aged 9-11 years from Ottawa, Ontario. The presence (yes/no) of a television (TV), computer or video game system in the child’s bedroom was reported by the parents. Percentage body fat was measured using bioelectrical impedance. An accelerometer was worn over seven days to assess moderate-to-vigorous physical activity (MVPA), total sedentary time, sleep duration and sleep efficiency. Screen time was self-reported by the child.RESULTS: After adjustment for age, sex, ethnicity, annual household income and highest level of parental education, children with 2-3 screens in their bedroom had a significantly higher percentage of body fat than children with no screen in their bedroom. However, while children with 2-3 screens in their bedroom engaged in more screen time overall than those with no screen, total sedentary time and MVPA were not significantly different. Sleep duration was not related to the number of screens in the bedroom, but sleep efficiency was significantly lower in children with at least 2 screens in the bedroom. Finally, children having only a TV in their bedroom had significantly higher adiposity than those having no screen at all. In contrast, the presence of a computer in children’s bedrooms was not associated with higher adiposity than that of children with no screen.CONCLUSIONS: A higher number of screens in a child’s bedroom was associated with higher adiposity, more total screen time and lower sleep efficiency. Having a TV in the bedroom appears to be the type of screen presence associated with higher levels of adiposity. Given the popularity of screens among children, these findings are increasingly relevant to health promotion strategies.RésuméOBJECTIF : Examiner si le nombre et le type d’écrans électroniques disponibles dans la chambre à coucher des enfants ont un lien avec leur adiposité, leur pratique d’activités physiques et leur sommeil.MÉTHODES : Une étude transversale a été réalisée auprès de 502 enfants âgés entre 9 et 11 ans provenant de la région d’Ottawa (Ontario). La présence (oui/non) d’un téléviseur, d’un ordinateur ou d’un jeu vidéo dans la chambre à coucher de l’enfant a été rapportée par les parents. Le pourcentage de graisse corporelle a été mesuré par impédance bioélectrique. Un accéléromètre a été porté sur une période de sept jours afin d’évaluer l’activité physique d’intensité moyenne à élevée, le temps sédentaire total, la durée ainsi que la qualité du sommeil.RÉSULTATS : Après ajustement statistique pour l’âge, le sexe, l’ethnicité, le revenu familial annuel et le niveau d’éducation parental, les enfants qui avaient 2 ou 3 écrans dans leur chambre à coucher avaient un pourcentage de gras significativement plus élevé que les enfants n’ayant aucun écran dans leur chambre à coucher. Alors que les enfants ayant 2 à 3 écrans dans leur chambre à coucher s’adonnaient à plus de temps écran total que ceux n’ayant pas d’écran, le temps sédentaire total et l’activité physique d’intensité moyenne à élevée n’étaient pas différentes entre les deux groupes. La durée du sommeil n’était pas reliée au nombre d’écrans dans la chambre à coucher alors que la qualité du sommeil était significativement moins bonne chez les enfants ayant au moins 2 écrans dans leur chambre à coucher. Finalement, les enfants ayant seulement un téléviseur dans leur chambre à coucher avaient une adiposité significativement plus élevée en comparaison à ceux qui n’avaient pas d’écrans du tout. Par contraste, la présence d’un ordinateur dans la chambre à coucher des enfants n’était pas associée avec une adiposité plus élevée.CONCLUSIONS : Un nombre plus élevé d’écrans dans la chambre à coucher des enfants est associé à une adiposité plus importante, davantage de temps écran total et une qualité de sommeil moins bonne. Avoir un téléviseur dans la chambre à coucher des enfants semble être le type de présence d’écran associé avec les niveaux d’adiposité les plus élevés. Étant donné la popularité des écrans chez les enfants, ces résultats sont d’une importance grandissante pour la formulation de stratégies de promotion en santé publique.

Television viewing and food intake during television viewing in normal-weight, overweight and obese 9- to 11-year-old Canadian children: a cross-sectional analysis

It is unclear if children of different weight status differ in their nutritional habits while watching television. The objective of the present paper was to determine if children who are overweight or obese differ in their frequency of consumption of six food items while watching television compared with their normal-weight counterparts. A cross-sectional study of 550 children (57·1 % female; mean age = 10 years) from Ottawa, Canada was conducted. Childrens weight status was categorised using the Centers for Disease Control and Prevention cut-points. Questionnaires were used to determine the number of hours of television watching per day and the frequency of consumption of six types of foods while watching television. Overweight/obese children watched more television per day than normal-weight children (3·3 v. 2·7 h, respectively; P = 0·001). Obese children consumed fast food and fruits/vegetables more frequently while watching television than normal-weight or overweight children (P < 0·05). Children who watched more than 4 h of television per d had higher odds (OR 3·21; 95% CI 1·14, 9·03; P = 0·03) of being obese, independent of several covariates, but not independent of moderate-to-vigorous physical activity. The finding that both television watching and the frequency of consumption of some food items during television watching are higher in children who are obese is concerning. While the nature of the present study does not allow for the determination of causal pathways, future research should investigate these weight-status differences to identify potential areas of intervention.

Comparison of ActiGraph GT3X+ and Actical accelerometer data in 9–11-year-old Canadian children

ABSTRACT Accelerometry is the gold standard for field-based physical activity assessment in children; however, the plethora of devices, data reduction procedures, and cut-points available limits comparability between studies. This study aimed to compare physical activity variables from the ActiGraph GT3X+ and Actical accelerometers in children under free-living conditions. A cross-sectional study of 379 children aged 9–11 years from Ottawa (Canada) was conducted. Children wore the ActiGraph GT3X+ and Actical accelerometers on the hip simultaneously for 7 consecutive days (24-h protocol). Moderate-to-vigorous (MVPA), vigorous (VPA), moderate (MPA), and light (LPA) physical activity, as well as sedentary time, (SED) were derived using established data reduction protocols. Excellent agreement between devices was observed for MVPA (ICC = 0.73–0.80), with fair to good agreement for MPA, LPA and SED, and poor agreement for VPA. Bland-Altman plots showed excellent agreement for MVPA, LPA, and SED, adequate agreement for MPA, and poor agreement for VPA. MVPA derived from the Actical was 11.7% lower than the ActiGraph GT3X+. The ActiGraph GT3X+ and Actical are comparable for measuring children’s MVPA. However, comparison between devices for VPA, MPA, LPA, and SED are highly dependent on data reduction procedures and cut-points, and should be interpreted with caution.