title: Prevalence of airflow limitation among employees in Norwegian smelters: a longitudinal study.
abstract: OBJECTIVE
  To investigate the association between airflow limitation and occupational exposure and to compare a fixed limit with an age adjusted limit for airflow limitation.
  
  
  METHODS
  3924 employees in 24 Norwegian smelters and related workplaces were investigated annually over 5 years (n=16, 570) using spirometry and a respiratory questionnaire on smoking habits and job category. Employees working full time on the production line were classified as line operators; subjects who never worked on the production line were regarded as non-exposed. A job exposure matrix (JEM) was available in most smelters. Airflow limitation was expressed as (i) forced expiratory volume in 1 s/forced vital capacity (FEV(1)/FVC ratio) <0.7 and (ii) FEV(1)/FVC ratio less than the lower limit of normal (LLN). Longitudinal analyses on the prevalence of airflow limitation were performed using a generalised linear mixed model.
  
  
  RESULTS
  The prevalence of airflow limitation was stable during follow-up. The OR of airflow limitation during follow-up was 1.24 (95% CI 1.03 to 1.50) in line operators compared with unexposed subjects for FEV(1)/FVC ratio <0.7 and 1.44 (1.14 to 1.81) for FEV(1)/FVC ratio <LLN. A dose-response relationship was also found between prevalence of airflow limitation and dust exposure. The annual decline in FEV(1) was -77.5 (SD 99.9) ml/year in subjects with FEV(1)/FVC ratio <0.7 and -83.8 (114.2) ml/year in subjects with FEV(1)/FVC ratio <LLN.
  
  
  CONCLUSIONS
  Prevalence of airflow limitation was higher in exposed than non-exposed employees. Both the FEV(1)/FVC ratio <0.7 and FEV(1)/FVC ratio <LLN identify subjects with accelerated annual decline in FEV(1).
authors.affiliation: Department of Medicine, Akershus University Hospital, University of Oslo, Lørenskog N-1478, Norway. vidar.soyseth@medisin.uio.no
authors.forename: Vidar
authors.initials: V
authors.lastname: Søyseth
authors.forename: Helle Laier
authors.initials: HL
authors.lastname: Johnsen
authors.forename: Merete Drevvatne
authors.initials: MD
authors.lastname: Bugge
authors.forename: Siri Merete
authors.initials: SM
authors.lastname: Hetland
authors.forename: Johny
authors.initials: J
authors.lastname: Kongerud
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000009:adverse effects* / Q000032:analysis; D004391:Dust; D004812:Epidemiologic Methods; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008669:Metallurgy; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D013147:Spirometry / Q000379:methods; D014797:Vital Capacity; D055815:Young Adult
chemical_list: D000395:Air Pollutants, Occupational; D004391:Dust