title: Body Mass Index of First Nations youth in Ontario, Canada: influence of sleep and screen time.
abstract: BACKGROUND
  Prevalence rates of overweight and obesity in Canada have risen rapidly in the past 20 years. Concurrent with the obesity epidemic, sleep time and physical activity levels have decreased among youth. Aboriginal youth experience disproportionately high obesity prevalence but there is inadequate knowledge of contributing factors. This research aimed to examine sleep and screen time behavior and their relationship to Body Mass Index (BMI) in on-reserve First Nations youth from Ontario, Canada.
  
  
  METHODS
  This was an observational population-based study of cross-sectional design. Self-reported physical activity, screen time, and lifestyle information was collected from 348 youth aged 10-18 years residing in five northern, remote First Nations communities and one southern First Nations community in Ontario, Canada, from October 2004 to June 2010. Data were collected in the school setting using the Waterloo Web-based Eating Behaviour Questionnaire. Based on self-reported height and weight, youth were classified normal (including underweight), overweight and obese according to BMI. Descriptive cross-tabulations and Pearson's χ² tests were used to compare screen time, sleep habits, and physical activity across BMI categories.
  
  
  RESULTS
  Participants demonstrated low levels of after-school physical activity, and screen time in excess of national guidelines. Overall, 75.5% reported being active in the evening three or less times per week. Approximately one-quarter of the surveyed youth watched more than 2 hours of television daily and 33.9% spent more than 2 hours on the internet or playing video games. For boys, time using the internet/video games (p=0.022) was positively associated with BMI category, with a greater than expected proportion of obese boys spending more than 2 hours using the internet or video games daily (56.7%). Also for boys, time spent outside after school (p=0.033) was negatively associated with BMI category, with a lesser than expected proportion spending 'most of the time' outside (presumably being active) after school. These relationships were not observed in girls. Adjusted standardized residuals suggest a greater than expected proportion of obese individuals had a television in their bedroom (66.7%) as compared with the rest of the population.
  
  
  CONCLUSIONS
  The current study adds to the limited information about contributors to overweight and obesity in First Nations youth living on-reserve in Canada. Concerns about inadequate sleep, excess screen time, and inadequate physical activity mirror those of the general population. Further investigation is warranted to improve the understanding of how various lifestyle behaviors influence overweight, obesity, and the development of chronic disease among First Nations youth. Initiatives to reduce screen time, increase physical activity, and encourage adequate sleep among on-reserve First Nations youth are recommended.
authors.affiliation: School of Public Health and Health Systems, University of Waterloo, Waterloo, Ontario, Canada. m2gates@uwaterloo.ca.
authors.forename: M
authors.initials: M
authors.lastname: Gates
authors.forename: R M
authors.initials: RM
authors.lastname: Hanning
authors.forename: I D
authors.initials: ID
authors.lastname: Martin
authors.forename: A
authors.initials: A
authors.lastname: Gates
authors.forename: L J S
authors.initials: LJ
authors.lastname: Tsuji
mesh_terms: D000293:Adolescent; D015992:Body Mass Index; D002648:Child; D015444:Exercise; D005260:Female; D006801:Humans; D007198:Indians, North American / Q000706:statistics & numerical data*; D020407:Internet; D008297:Male; D009765:Obesity / Q000208:ethnology; D009864:Ontario / Q000453:epidemiology; D050177:Overweight / Q000208:ethnology*; D015995:Prevalence; D057185:Sedentary Behavior / Q000208:ethnology; D012890:Sleep