Overestimation of peer smoking prevalence predicts smoking initiation among primary school students in Hong Kong.

PURPOSE 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. CONCLUSION 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.