Sedentary behavior in a cohort of 8- to 10-year-old children at elevated risk of obesity
Introduction
Sedentary behavior (SB) has emerged as a separate construct from physical inactivity, rather than simply representing the low end of the physical activity (PA) continuum or an absence of moderate-to-vigorous PA (MVPA) (Tremblay et al., 2010). SB refers to any waking behavior characterized by low energy expenditure (≤ 1.5 METs) while in a sitting or reclining posture (Owen et al., 2010, Pate et al., 2008, Sedentary Behaviour Research Network, 2012). This includes sitting for long periods, use of motorized transportation, television viewing, playing passive video games or using the computer (Tremblay et al., 2011a). Importantly, even individuals classified as “active” or meeting PA guidelines can simultaneously be highly sedentary, as the former accounts for minimal time per day (Tremblay et al., 2011c). SB is associated with health consequences distinct from those of inactivity and independent from the health benefits of PA (Ekelund et al., 2006, Healy et al., 2008, Owen et al., 2010, Tremblay et al., 2010).
On average, Canadian children spend 8.6 h/day (62% of their waking hours) in SB (Colley et al., 2011). Further, ≥ 6 h/day are spent in front of a screen (television or computer) (Active Healthy Kids Canada, 2012), despite current guidelines recommending ≤ 2 h/day of recreational screen time (Tremblay et al., 2011a). Among different SBs, screen time specifically has been shown to be associated with weight status and obesity in children (Epstein et al., 2008, Fulton et al., 2009, Saelens et al., 2002). Studies routinely assess SB either objectively by accelerometry, or subjectively by self-report. Accelerometers may accurately identify time spent in SB, but do not provide information about the type of SB engaged in, of importance as not all SBs show the same negative associations with health outcomes. (Gopinath et al., 2012, Sisson et al., 2011) On the other hand, more descriptive self-report measures may suffer from recall biases with respect to time spent. It has been recommended that these two methods be used in conjunction, providing complimentary information thereby more accurately describing SB (Lubans et al., 2011). However, to date, few studies have attempted to comprehensively describe SB in children using both objective and subjective measures. Improved the understanding of childhood SB is critical in order to identify targets for intervention, particularly since SB may track better than PA over time (Biddle et al., 2010, Janz et al., 2005).
The objectives of this study were to comprehensively describe SB in a cohort of children aged 8–10 years at elevated risk of obesity due to parental obesity, using both objective and subjective measures of SB. Specifically, (a) to describe time spent in different SBs according to total objectively measured SB time, including differences by sex and weight status, and (b) to investigate the concept of SB in otherwise active children, by estimating prevalence in various combined PA/SB groups. A subobjective of the study was to evaluate the association between SB time and accelerometer wear time.
Section snippets
Study sample
Data were from the baseline visit of the Quebec Adipose and Lifestyle Investigation in Youth (QUALITY) study; in-depth methodology has previously been published. (Lambert et al., 2012) Briefly, the QUALITY study aims to describe the development of childhood obesity and its metabolic and cardiovascular consequences. The cohort includes 630 Caucasian children aged 8–10 years at baseline (2005–2008), and their 2 biological parents of whom at least 1 is clinically obese (BMI ≥ 30 kg/m2, or waist
Results
Approximately 40% of the children were overweight/obese, and close to 25% had a waist circumference exceeding the 90th percentile (Table 1). Only 56% of girls and 38% of boys met screen time guidelines (≤ 2 h/day), and children accumulated a mean of approximately 6 h/day total SB time (no difference boys vs. girls). About 46% of boys but only 15% of girls accumulated a mean of ≥ 60 min/day MVPA. With respect to both total accelerometer SB time as well as television and total screen time,
Discussion
The objectives of this study were to describe SB in 8- to 10-year-old Canadian children at elevated risk of obesity due to parental obesity, using objectively measured SB time as an outcome by which to describe and compare specific self-reported SBs, and to investigate the concept that high levels of SB are possible even in “active” children. The results indicate that overweight/obese children have higher overall SB time and screen time compared to normal weight 7children. Much total SB time
Conclusions
Overweight/obese children are more sedentary and report more screen time than normal weight children; however, much total SB time in children remains unaccounted for by self-reports of specific behaviors, especially in the most sedentary children. Further research is needed to continue to develop means of gathering more comprehensive data in order to better elucidate the full nature of SB. Public health efforts aimed at reducing screen time and increasing PA in children should consider sex and
Conflict of Interest Statement
The authors declare that there are no conflicts of interest.
Acknowledgments
The research team is grateful to all the children and their families who took part in this study as well as the technicians, research assistants and coordinators involved in the QUALITY cohort project. Dr. Marie Lambert (July 1952–February 2012), pediatric geneticist and researcher, initiated the QUALITY cohort. Her leadership and devotion to QUALITY will always be remembered and appreciated. The QUALITY study is funded by the Canadian Institutes of Health Research, the Heart and Stroke
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