[Factors associated with smoking onset: 3-year cohort study of schoolchildren]

To analyze the predictors of smoking onset among schoolchildren.

A cohort study of 1056 children starting in first year secondary school at 44 schools in Barcelona was carried out. Participating children were invited to answer a lifestyle questionnaire every year for 4 years. Each questionnaire carried a personal code to allow the 4 questionnaires to be matched. Matching questionnaires were found for 729 children, 70% of the initial sample.

Over the study period, the prevalence of regular smokers increased from 1.7% to 22% among boys and from 1.6% to 38.2% among girls. The predictors of smoking onset among boys were scoring high on the pro-smoking attitudes index (odds ratio [OR]=1.2; 95% confidence interval [CI], 1.1-1.3), intention to smoke in the future (OR=2.2; 95% CI, 1.0-4.9), low self-efficacy in resisting pressures to smoke (OR=0.98; 95% CI, 0.96-0.99), having siblings that smoke (OR=2.5; 95% CI, 1.2-5.4), and spending some free time in bars (OR=2.4; CI, 1.1-4.9). Among girls, the predictors were having low self-esteem (OR=0.94; 95% CI, 0.88-0.99), scoring low on the anti-tobacco attitudes index (OR=0.92; 95% CI, 0.88-0.97), having siblings who smoke (OR=2.5; 95% CI, 1.2-5.5), spending some free time in discotheques (OR=4.5; 95% CI, 1.9-11.8), and living in high socioeconomic-status neighborhoods (OR=3.1; 95% CI, 1.4-10.9).

The results show the importance of cognitive variables as well as a variety of environmental variables, particularly the pattern of free time use and the influence of sibling models. Prevention programs must take into account smoking onset risk factors as a whole.