title: Physical activity inversely associated with the presence of depression among urban adolescents in regional China.
abstract: BACKGROUND
  An inverse relationship between physical activity (PA) and depression among adolescents has been reported in developed communities without consideration of sedentary behaviors (SB, including sitting for course study, viewing TV, and sleeping). We explored the association between recreational PA time (hr/wk) and depression after adjustment with SB and other possible confounders among Chinese adolescents.
  
  
  METHODS
  A population-based cross-sectional study was conducted in Nanjing municipality of China in 2004 using a multi-stage cluster sampling approach. A total of 72 classes were randomly selected from 24 urban junior high schools and all students completed the structured questionnaire. Adolescent depression was examined by the Children's Depression Inventory (CDI) of Chinese version with cutoff point value of 20 or above as the presence of depression. Recreational PA time was measured by a question on weekly hours of PA outside of school. Descriptive statistics, multivariate logistic and linear regression models were used in analysis.
  
  
  RESULTS
  The overall prevalence of depression was 15.7% (95%CI: 14.3%, 17.1%) among 2,444 eligible participants. It was found that physical activity was negatively associated with depression. After adjustment for sedentary behaviors and other potential confounders, participants who spent 1-7 hr/wk, 8-14 hr/wk and 15+ hr/wk for recreational PA, respectively, had odds ratios of 0.70 (95% CI = 0.57, 0.86), 0.68 (95% CI = 0.53, 0.88) and 0.66 (95% CI = 0.50, 0.87) for likelihood of being depressive, compared to their counterparts who spent 0-0.9 hr/wk for PA. This inverse relationship between PA time and depression remained statistically significant by gender and grade.
  
  
  CONCLUSIONS
  This study, conducted among Chinese adolescents, strengthened the evidence that physical activity was inversely associated with depression. Our study has important implications for health officers and public health professionals to pay much attention to the relationship between physical activity and depression in Mainland China.
authors.affiliation: Nanjing Municipal Center for Disease Control & Prevention, Nanjing, PR China. nj_hongxin@hotmail.com
authors.forename: Xin
authors.initials: X
authors.lastname: Hong
authors.forename: JieQuan
authors.initials: J
authors.lastname: Li
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.forename: Lap Ah
authors.initials: LA
authors.lastname: Tse
authors.forename: YaQiong
authors.initials: Y
authors.lastname: Liang
authors.forename: ZhiYong
authors.initials: Z
authors.lastname: Wang
authors.forename: Ignatius Tak-sun
authors.initials: IT
authors.lastname: Yu
authors.forename: Sian
authors.initials: S
authors.lastname: Griffiths
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D015992:Body Mass Index; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003863:Depression / Q000453:epidemiology* / Q000517:prevention & control / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D015999:Multivariate Analysis; D015995:Prevalence; D011998:Recreation / Q000502:physiology / Q000523:psychology; D012923:Social Class; D011795:Surveys and Questionnaires; D014504:Urban Health