Objectively-measured sleep and its association with adiposity and physical activity in a sample of Canadian children JESSICA MCNEIL 1,2 , MARK S. TREMBLAY 1,2,3,4 , GENEVI  EVE LEDUC 1 , CHARLES BOYER 1 , PRISCILLA B  ELANGER 1 , ALLANA G. LEBLANC 1,4 , MICHAEL M. BORGHESE 1,2 andJEAN-PHILIPPECHAPUT 1,2,3,4 1 Healthy Active Living and Obesity Research Group, Children’s Hospital of Eastern Ontario Research Institute, Ottawa, ON, Canada; 2 School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, Ottawa, ON, Canada; 3 Department of Pediatrics, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada; 4 Population Health, Faculty of Graduate and Postdoctoral Studies, University of Ottawa, Ottawa, ON, Canada Keywords anthropometric measurements, exercise, sedentary behavior, sleep patterns Correspondence Jean-Philippe Chaput, PhD, Healthy Active Living and Obesity Research Group (HALO), Children’s Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Room R240, Ottawa, Ontario, K1H 8L1, Canada. Tel.: 1-613-737-7600 ext. 3683; fax: 1-613-738-4800; e-mail: jpchaput@cheo.on.ca Accepted in revised form 10 August 2014; received 15 April 2014 DOI: 10.1111/jsr.12241 SUMMARY Cross-sectional associations between objectively-measured sleep dura- tion, 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 Æ 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. INTRODUCTION Many cross-sectional studies have previously noted that children who sleep less than the recommended 10 h per night have a greater body mass index (BMI) z-score (Bornhorst et al., 2012; Chaput et al., 2011; Colley et al., 2012; Ekstedt et al., 2013; Meng et al., 2012; Nixon et al., 2008; Stone et al., 2013), waist circumference (Chaput et al., 2011; Jarrin et al., 2013; Meng et al., 2012) and fat mass (Bornhorst et al., 2012; Chaput et al., 2011; Nixon et al., 2008) than children who sleep >10 h per night. Furthermore, studies have observed that short sleep duration (<9 or 10 h per night) is associated with an increased risk of being overweight/obese in children (adjusted odds ratios ranging from 1.29 to 4.96), indepen- dently of a number of well-known covariates such as physical activity, energy intake, family income and parental BMI (Chaput et al., 2011; de Jong et al., 2012; Meng et al., 2012; Nixon et al., 2008; Shi et al., 2010). Studies assessing the ª 2014 European Sleep Research Society 1 J Sleep Res. (2014) Regular Research Paper