title: Contextual factors associated with smoking among Brazilian adolescents.
abstract: BACKGROUND
  Very few studies have examined the role of school, household and family contexts in youth smoking in middle-income countries.
  
  
  METHODS
  This work describes smoking exposure among 59,992 high school students who took part in the Brazilian Survey of School Health and investigates contextual factors associated with regular smoking, defined as smoking cigarettes at least once in the past 30 days. The explaining variables were grouped into: socio-demographic characteristics, school context, household context and family rapport. Variables independently associated with smoking in each context were identified by multiple logistic regression analysis.
  
  
  RESULTS
  53% of the total sample were girls, 89% were aged 13-15 years. 24% had already experimented with cigarettes, 50% before the age of 12 years. The prevalence of regular smoking was 6.3% (95% CI 5.87 to 6.74), with no sex variation. Smoking was not associated with either the mother's education or the index of household assets. In the multivariable analysis, studying at a private school, the possibility of purchasing cigarettes at school and skipping of classes without parents' consent increased the chances of smoking. In the household context, living with both parents was negatively associated with smoking, while having smoking parents and exposure to other people's smoking was positively related to smoking. In the family context, parental unawareness of what the adolescent was doing increased smoking, but having meals with the mother one or more days per week and parents' negative reactions to adolescent smoking reduced the chances of smoking.
  
  
  CONCLUSIONS
  The results reinforce the role of school, household and family contexts in youth smoking behaviours and will help improve public health policies aimed at preventing smoking and health promotion in adolescents.
authors.affiliation: Faculty of Medicine, Universidade Federal de Minas Gerais, Av Alfredo Balena 190, sl 814, Belo Horizonte, CEP 30130100, Minas Gerais, Brazil. barreto@medicina.ufmg.br
authors.forename: Sandhi Maria
authors.initials: SM
authors.lastname: Barreto
authors.forename: Luana
authors.initials: L
authors.lastname: Giatti
authors.forename: Leticia
authors.initials: L
authors.lastname: Casado
authors.forename: Lenildo
authors.initials: L
authors.lastname: de Moura
authors.forename: Claudio
authors.initials: C
authors.lastname: Crespo
authors.forename: Deborah
authors.initials: D
authors.lastname: Malta
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005191:Family Characteristics; D005260:Female; D015438:Health Behavior / Q000208:ethnology; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010287:Parent-Child Relations / Q000208:ethnology; D015995:Prevalence; D017149:Private Sector / Q000706:statistics & numerical data; D017150:Public Sector / Q000706:statistics & numerical data; D012572:School Health Services; D017678:Sex Distribution; D012907:Smoking / Q000453:epidemiology*; D012923:Social Class; D012959:Socioeconomic Factors; D013334:Students / Q000523:psychology* / Q000706:statistics & numerical data; D011795:Surveys and Questionnaires; D014505:Urban Population / Q000706:statistics & numerical data