title: Smoking and asthma: disentangling their mutual influences using a longitudinal approach.
abstract: BACKGROUND
  The association between smoking and asthma remains unclear and has mostly been assessed in cross-sectional studies, with potential selection bias ("healthy smoker effect").
  
  
  OBJECTIVE
  Using a longitudinal approach, the aims were to assess whether 1) childhood asthma modifies smoking initiation, 2) active smoking influences asthma incidence in adults and 3) active smoking among subjects with asthma influences the persistence of the disease or the 12-year evolution in lung function in children and adults.
  
  
  METHODS
  Subjects (513 children and 1190 adults) were recruited and followed-up for 12 years in the context of the EGEA study (Epidemiological study on the Genetics and Environment of Asthma).
  
  
  RESULTS
  Childhood asthma was not associated with a decreased probability of starting active smoking (Hazard Ratio, HR = 0.96; 95% confidence interval (CI): 0.72, 1.27). Smoking at baseline was associated with a higher risk for asthma incidence in adulthood (HR = 1.95, 95% CI: 1.00, 3.77). Among subjects with asthma, smoking was unrelated to lung function evolution; however, among children with moderate to severe asthma at inclusion, smoking tended to slow down the lung function growth (P = 0.04).
  
  
  CONCLUSIONS
  These findings support the hypothesis that childhood asthma does not prevent smoking initiation and confirm that active smoking has a deleterious role on asthma. Altogether this study emphasizes the importance of active smoking as a serious public health problem particularly for children and women.
authors.affiliation: Centre de Recherche INSERM/UJF U823, Institut Albert Bonniot, BP 170, 38042 Grenoble Cedex 9, La Tronche, France. lucile.vignoud@ujf-grenoble.fr
authors.forename: Lucile
authors.initials: L
authors.lastname: Vignoud
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pin
authors.forename: Anne
authors.initials: A
authors.lastname: Boudier
authors.forename: Christophe
authors.initials: C
authors.lastname: Pison
authors.forename: Rachel
authors.initials: R
authors.lastname: Nadif
authors.forename: Nicole
authors.initials: N
authors.lastname: Le Moual
authors.forename: Remy
authors.initials: R
authors.lastname: Slama
authors.forename: Molière Nguile
authors.initials: MN
authors.lastname: Makao
authors.forename: Francine
authors.initials: F
authors.lastname: Kauffmann
authors.forename: Valérie
authors.initials: V
authors.lastname: Siroux
mesh_terms: D000328:Adult; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D002648:Child; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012129:Respiratory Function Tests; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology* / Q000503:physiopathology; D013997:Time Factors