title: Overestimation of peer smoking prevalence predicts smoking initiation among primary school students in Hong Kong.
abstract: OBJECTIVE
  To investigate the relationship between perceived prevalence of smoking and smoking initiation among Hong Kong primary second- to fourth-grade-students.
  
  
  METHODS
  A cohort of 2,171 students was surveyed in 2006 and again in 2008. Students who perceived ever-smoking prevalence in peers as "none" or "some" were considered as correct (reference group), whereas those who perceived it as "half" (overestimation) or "most/all" (gross overestimation) were considered as incorrect.
  
  
  RESULTS
  At baseline, overestimation was found to be cross-sectionally associated with ever-smoking (p < .01). At follow-up, 7.2% of never-smoking students with incorrect estimation at baseline had started smoking, which was 79% (95% confidence interval: 3%-213%), greater than that of 3.7% for those with correct estimation. Among the never-smoking students with incorrect estimation, subsequent correct estimation was associated with 70% (95% confidence interval: 47%-83%) lower risk of smoking initiation compared with persistent incorrect estimation.
  
  
  CONCLUSIONS
  Overestimation of the prevalence of peer smoking predicted smoking initiation among children. Interventions should be carried out to evaluate whether correcting children's overestimation of peer smoking could reduce smoking initiation.
authors.affiliation: School of Public Health, University of Hong Kong, Hong Kong, PR China.
authors.forename: Man Ping
authors.initials: MP
authors.lastname: Wang
authors.forename: Sai Yin
authors.initials: SY
authors.lastname: Ho
authors.forename: Wing Sze
authors.initials: WS
authors.lastname: Lo
authors.forename: Tai Hing
authors.initials: TH
authors.lastname: Lam
mesh_terms: D015982:Bias; D002648:Child; D015331:Cohort Studies; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D005260:Female; D005544:Forecasting; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D008297:Male; D016017:Odds Ratio; D010379:Peer Group; D012907:Smoking / Q000453:epidemiology*