title: Modifiable characteristics associated with sedentary behaviours among youth.
abstract: OBJECTIVE
  Childhood overweight and obesity is a major public health issue. A better understanding of factors associated with sedentary behaviours would provide valuable insight for tailoring interventions to prevent or reduce overweight among youth.
  
  
  METHODS
  Data were collected from 25,416 grade 9 to 12 students attending 76 secondary schools in Ontario, Canada, using the Physical Activity Module of the School Health Action, Planning and Evaluation System (SHAPES). Sex specific multivariate logistic regression analyses were then used to examine how physical activity, BMI, social influences, and smoking behaviour were associated with screen time, time spent reading, and time spent on homework.
  
  
  RESULTS
  The average screen time per day was 2.7 (+/-1.7) hours, yet 48.1% of students reported spending less than one hour reading per week and 30.2% spent less than an hour of time on homework per week. Among males, being underweight (< or = 5% percentile BMI, adjusted for age and sex) was associated with more screen time (OR 1.23, 95%CI 1.01-1.50) and time spent reading (OR 1.19, 95%CI 1.00-1.43), whereas being at risk of overweight (> or = 85% percentile BMI, adjusted for age and sex) was associated with less time spent on homework (OR 0.75, 95%CI 0.65-0.85). Conversely, among females, being at risk of overweight was associated with more screen time (OR 1.24, 95%CI 1.10-1.41), and time spent reading (OR 1.19, 95%CI 1.05-1.35). Aside from BMI, other factors associated with sedentary behaviours included physical activity, parental encouragement and support for physical activity, close friend physical activity behaviour, and smoking status.
  
  
  CONCLUSIONS
  We found that students are highly involved in screen-based sedentary behaviours, but spend a limited time on more productive sedentary behaviours, like reading and homework. Developing a better understanding of sedentary behaviours is critical for preventing and reducing obesity among youth populations.
authors.affiliation: Division of Preventive Oncology, Cancer Care Ontario, Toronto ON, Canada, M5G 2L7. scott.leatherdale@cancercare.on.ca
authors.forename: Scott T
authors.initials: ST
authors.lastname: Leatherdale
authors.forename: Suzy L
authors.initials: SL
authors.lastname: Wong
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D015992:Body Mass Index; D003201:Computers; D003430:Cross-Sectional Studies; D005260:Female; D015438:Health Behavior; D006801:Humans; D007899:Leisure Activities; D008019:Life Style; D016015:Logistic Models; D008297:Male; D009043:Motor Activity; D009765:Obesity / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control / Q000523:psychology; D016017:Odds Ratio; D009864:Ontario / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control / Q000523:psychology; D010287:Parent-Child Relations; D011932:Reading; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects; D012919:Social Behavior; D013997:Time Factors