The course of early smoking: a population-based cohort study over three years

Aims. To examine the uptake and course of smoking in a representative adolescent cohort. Design. Six-wave cohort study. Participants. Secondary school students initially aged 14-15 years at 44 schools in the state of Victoria, Australia. Measurements. Computerized questionnaire including 7-day retrospective recall for tobacco use. Findings. Prevalence rates for smoking in the past month rose from 25% to 31% and daily smoking 9% to 18% across the 3-year follow-up. Forty-five per cent of the sample smoked at some point but only 18% were daily smokers at the end-point. High rates of short-term cessation were observed for both experimental and daily smokers, but 70% of daily smokers relapsed within 12 months. Occasional smoking at the outset was the strongest predictor of later daily smoking and was also predictive of lower cessation and higher relapse rates. Parental divorce and parental daily smoking were associated with smoking at the outset and parental smoking was strongly predictive of the course of daily smoking. In contrast, prevalence rates of smoking in a subject's school did not significantly predict either smoking initiation or subsequent course. Female daily smokers were half as likely as males to cease smoking, a finding that accounted for gender differences in smoking prevalence in this sample. Conclusions. The strength of association between occasional and later daily smoking indicates the importance of primary prevention but the variability in the early course indicates that there should be much scope for promotion of adolescent efforts to quit. Both the diminished likelihood of smoking cessation in young women and parental influences on smoking course deserve further exploration.