title: Regular smoking and asthma incidence in adolescents.
abstract: BACKGROUND
  Although involuntary exposure to maternal smoking during the in utero period and to secondhand smoke are associated with occurrence of childhood asthma, few studies have investigated the role of active cigarette smoking on asthma onset during adolescence.
  
  
  OBJECTIVE
  To determine whether regular smoking is associated with the new onset of asthma during adolescence.
  
  
  METHODS
  We conducted a prospective cohort study among 2,609 children with no lifetime history of asthma or wheezing who were recruited from fourth- and seventh-grade classrooms and followed annually in schools in 12 southern California communities. Regular smoking was defined as smoking at least seven cigarettes per day on average over the week before and 300 cigarettes in the year before each annual interview. Incident asthma was defined using new cases of physician-diagnosed asthma.
  
  
  RESULTS
  Regular smoking was associated with increased risk of new-onset asthma. Children who reported smoking 300 or more cigarettes per year had a relative risk (RR) of 3.9 (95% confidence interval [95% CI], 1.7-8.5) for new-onset asthma compared with nonsmokers. The increased risk from regular smoking was greater in nonallergic than in allergic children. Regular smokers who were exposed to maternal smoking during gestation had the largest risk from active smoking (RR, 8.8; 95% CI, 3.2-24.0).
  
  
  CONCLUSIONS
  Regular smoking increased risk for asthma among adolescents, especially for nonallergic adolescents and those exposed to maternal smoking during the in utero period.
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine of USC, 1540 Alcazar Street, CHP 236, Los Angeles, CA 90033, USA. gillilan@usc.edu
authors.forename: Frank D
authors.initials: FD
authors.lastname: Gilliland
authors.forename: Talat
authors.initials: T
authors.lastname: Islam
authors.forename: Kiros
authors.initials: K
authors.lastname: Berhane
authors.forename: W James
authors.initials: WJ
authors.lastname: Gauderman
authors.forename: Rob
authors.initials: R
authors.lastname: McConnell
authors.forename: Edward
authors.initials: E
authors.lastname: Avol
authors.forename: John M
authors.initials: JM
authors.lastname: Peters
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001249:Asthma / Q000453:epidemiology*; D002140:California / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D018811:Maternal Exposure; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012907:Smoking / Q000453:epidemiology* / Q000503:physiopathology; D014028:Tobacco Smoke Pollution
chemical_list: D014028:Tobacco Smoke Pollution