title: Airway hyperresponsiveness and risk of chest symptoms in an occupational model.
abstract: BACKGROUND
  The clinical outcome of asymptomatic airway hyperresponsiveness (AHR) remains unclear. A study was undertaken to evaluate the incidence of respiratory symptoms in a cohort of asymptomatic subjects with AHR at baseline.
  
  
  METHODS
  A 3 year prospective study involving methacholine challenge tests and serially administered questionnaires was undertaken in 769 apprentices exposed to high molecular weight allergens. Analyses were performed on 428 initially asymptomatic subjects.
  
  
  RESULTS
  Thirty eight subjects (8.9%) were airway hyperresponsive (PC(20) < or =8 mg/ml) and asymptomatic at the start of the study. Forty four apprentices (10.3%) developed two or more respiratory symptoms unrelated to work, 13 (34.2%) in the AHR group and 31 (7.9%) in the non-AHR group (risk ratio (RR) 7.88 (95% CI 2.53 to 24.55) among subjects with AHR). The RR of developing two or more respiratory symptoms increased as the degree of PC(20) decreased with a significant trend (p<0.001). In a multivariate analysis, AHR (RR 8.33, 95% CI 2.65 to 26.16) and self-reported rhinitis on exposure to pollen through an interaction with a family history of asthma (RR 6.3, 95% CI 1.29 to 31.89) were associated with the incidence of two or more respiratory symptoms; atopy was not a significant covariate.
  
  
  CONCLUSIONS
  AHR in asymptomatic subjects is an important determinant for the development of respiratory symptoms outside the workplace among apprentices exposed to high molecular weight allergens in their training environment.
authors.affiliation: Department of Chest Medicine, Hôpital du Sacré-Coeur, 5400 Gouin Blvd West, Montreal, Canada, H4J 1C5.
authors.forename: K
authors.initials: K
authors.lastname: Boutet
authors.forename: J-L
authors.initials: JL
authors.lastname: Malo
authors.forename: H
authors.initials: H
authors.lastname: Ghezzo
authors.forename: D
authors.initials: D
authors.lastname: Gautrin
mesh_terms: D000293:Adolescent; D000328:Adult; D000485:Allergens / Q000633:toxicity*; D016535:Bronchial Hyperreactivity / Q000139:chemically induced* / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000379:methods; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D009784:Occupational Diseases / Q000139:chemically induced* / Q000503:physiopathology; D016273:Occupational Exposure; D011446:Prospective Studies; D012120:Respiration Disorders / Q000139:chemically induced* / Q000503:physiopathology; D012130:Respiratory Hypersensitivity / Q000175:diagnosis* / Q000503:physiopathology; D012307:Risk Factors; D012882:Skin Tests; D014797:Vital Capacity / Q000502:physiology
chemical_list: D000485:Allergens