title: [Smoking initiation in students: cross-sectional and longitudinal study of predictive factors].
abstract: BACKGROUND
  This study examines the evolution of tobacco use among schoolchildren in sixth and seventh grades in Barcelona (11-13 years) and identifies smoking risk factors through cross-sectional and follow-up analysis. POBLATION AND METHODS: The cohort consists of 1,003 students attending 13 schools who served as control units for a study assessing the effects of a school-based addictive substances prevention program. Participants answered the same questionnaire in 1990 and 1991. Risk factors for the experimentation and for regular smoking are studied through cross-sectional and prospective studies.
  
  
  RESULTS
  In a year, smokers increase from 9.7% to 18.9% and regular smokers rise from 1.1% to 5.5%. The initial cross-sectional analysis finds stronger associations than the follow-up one. Some variables loose their significance in the longitudinal analysis. Among non-smokers, the strongest predictors to emerge are intention to smoke, the belief that smoking is fun, peers, siblings and mother consumption, and being male; however girls appear to consolidate the consumption more than boys among the cohort of triers.
  
  
  CONCLUSIONS
  Tobacco use prevalences are consistent with other studies developed in our city. Social environment emerges as an important predictor; friends, siblings and mothers tobacco use and gender are the main risk factors.
authors.affiliation: Institut Municipal de la Salut, Ajuntament de Barcelona.
authors.forename: E
authors.initials: E
authors.lastname: Díaz
authors.forename: J R
authors.initials: JR
authors.lastname: Villalbí
authors.forename: M
authors.initials: M
authors.lastname: Nebot
authors.forename: J
authors.initials: J
authors.lastname: Aubà
authors.forename: F
authors.initials: F
authors.lastname: Sanz
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D012907:Smoking / Q000453:epidemiology*