title: Longitudinal sedentary behavior changes in adolescents in Ho Chi Minh City.
abstract: BACKGROUND
  Sedentary behavior is associated with increased risk of chronic disease and sedentary behavior is increasing among adolescents. Data on changes in sedentary behavior in developing countries are limited.
  
  
  OBJECTIVE
  To describe 5-year longitudinal changes in nonschool sedentary hours among urban adolescents in Ho Chi Minh City, and to identify correlates with this change.
  
  
  METHODS
  This is a 5-year longitudinal cohort with systematic random sampling of 759 students from 18 junior high schools. All measures were taken annually between 2004 and 2009. Sedentary behavior was assessed by self-report and accelerometry. Generalized linear latent and mixed models were used to analyze the data in 2011.
  
  
  RESULTS
  Between 2004 and 2009, self-reported time spent in nonschool sedentary behavior increased from 498 to 603 minutes/day. In the 5th survey year, boys and girls (aged 16 years) were, respectively, 3.6 times (95% CI=2.3, 6.0) and 3.1 times (95% CI= 1.8, 5.0) more likely to spend ≥2 hours/day on screen time compared with baseline (aged 12 years). Accelerometer data adjusted for wearing time revealed that boys and girls aged 16 years had, respectively, 78 minutes/day (95% CI=48, 104) and 69 minutes/day (95% CI=34, 95) more nonschool sedentary time than those at the first accelerometer assessment (at age 13 years). Girls in the highest socioeconomic quartile spent an additional 90 minutes/day in sedentary behavior compared with girls in the lowest quartile (95% CI=52, 128).
  
  
  CONCLUSIONS
  Nonschool sedentary behavior increased among Vietnamese adolescents with age. The largest increase was in recreational screen time (28%), which would be the most obvious target for preventive health strategies.
authors: Department of Community Health, Pham Ngoc Thach University of Medicine, Ho Chi Minh City, Vietnam. nguyenhoang_doantrang@yahoo.com
authors: Nguyen H H D
authors: NH
authors: Trang
authors: Tang K
authors: TK
authors: Hong
authors: Hidde P
authors: HP
authors: van der Ploeg
authors: Louise L
authors: LL
authors: Hardy
authors: Patrick J
authors: PJ
authors: Kelly
authors: Michael J
authors: MJ
authors: Dibley
mesh_terms: D061725:Accelerometry; D000293:Adolescent; D000367:Age Factors; D015992:Body Mass Index; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012307:Risk Factors; D057185:Sedentary Behavior; D057566:Self Report; D012737:Sex Factors; D012959:Socioeconomic Factors; D014505:Urban Population / Q000706:statistics & numerical data*; D014744:Vietnam / Q000453:epidemiology