title: [Smoking and its associated factors in Portuguese adolescent students].
abstract: OBJECTIVE
  To describe smoking habits and to identify their determinants in adolescent students.
  
  
  METHODS
  A cross-sectional study was carried out on smoking habits comprising 1,052 girls and 984 boys aged 13 years attending public and private schools in the city of Porto, Portugal. The proportion of participation was 77.5%. Information on sociodemographic and behavioral characteristics was obtained from a questionnaire filled out at home by participants and their parents. At school, another self-administered questionnaire was used to obtain information about tobacco use. Several independent samples were compared using the Kruskal-Wallis test and proportions were compared by Chi-square test. Odds ratio and 95% confidence intervals were calculated by unconditional logistic regression.
  
  
  RESULTS
  Overall, 19.9% (22.4% of girls and 17.1% of boys) students only had ever experimented smoking but were not smokers; 1.8% (2.0% of girls and 1.5% of boys) were occasional smokers and 1.3% (2.0% of girls and 0.4% of boys) smoked at least one cigarette/day. Curiosity was the main reason given by adolescents to experiment smoking (48.4% of girls and 45.6% of boys). After adjustment to parental, siblings' and friends' smoking habits, the stronger association was with the smoking habits of their friends for both girls (OR=4.03; 95% CI: 2.69-6.04) and boys (OR=5.39; 95% CI: 3.34-8.70).
  
  
  CONCLUSIONS
  A high proportion of students had ever experimented smoking. Smoking habits among peers proved to be the strongest determinant of smoking during adolescence.
authors.affiliation: Serviço de Higiene e Epidemiologia, Faculdade de Medicina, Universidade do Porto, Porto, Portugal. silfraga@med.up.pt
authors.forename: Sílvia
authors.initials: S
authors.lastname: Fraga
authors.forename: Elisabete
authors.initials: E
authors.lastname: Ramos
authors.forename: Henrique
authors.initials: H
authors.lastname: Barros
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D004812:Epidemiologic Methods; D005195:Family Relations; D005260:Female; D006801:Humans; D008297:Male; D011174:Portugal / Q000453:epidemiology; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D012959:Socioeconomic Factors; D013334:Students / Q000706:statistics & numerical data*