title: Previous lung diseases and lung cancer risk: a systematic review and meta-analysis.
abstract: BACKGROUND
  In order to review the epidemiologic evidence concerning previous lung diseases as risk factors for lung cancer, a meta-analysis and systematic review was conducted.
  
  
  METHODS
  Relevant studies were identified through MEDLINE searches. Using random effects models, summary effects of specific previous conditions were evaluated separately and combined. Stratified analyses were conducted based on smoking status, gender, control sources and continent.
  
  
  RESULTS
  A previous history of COPD, chronic bronchitis or emphysema conferred relative risks (RR) of 2.22 (95% confidence interval (CI): 1.66, 2.97) (from 16 studies), 1.52 (95% CI: 1.25, 1.84) (from 23 studies) and 2.04 (95% CI: 1.72, 2.41) (from 20 studies), respectively, and for all these diseases combined 1.80 (95% CI: 1.60, 2.11) (from 39 studies). The RR of lung cancer for subjects with a previous history of pneumonia was 1.43 (95% CI: 1.22-1.68) (from 22 studies) and for subjects with a previous history of tuberculosis was 1.76 (95% CI=1.49, 2.08), (from 30 studies). Effects were attenuated when restricting analysis to never smokers only for COPD/emphysema/chronic bronchitis (RR=1.22, 0.97-1.53), however remained significant for pneumonia 1.36 (95% CI: 1.10, 1.69) (from 8 studies) and tuberculosis 1.90 (95% CI: 1.45, 2.50) (from 11 studies).
  
  
  CONCLUSIONS
  Previous lung diseases are associated with an increased risk of lung cancer with the evidence among never smokers supporting a direct relationship between previous lung diseases and lung cancer.
authors.affiliation: Samuel Lunenfeld Research Institute of Mount Sinai Hospital, and The Dalla Lana School of Public Health, University of Toronto, Toronto, Canada.
authors.forename: Darren R
authors.initials: DR
authors.lastname: Brenner
authors.forename: John R
authors.initials: JR
authors.lastname: McLaughlin
authors.forename: Rayjean J
authors.initials: RJ
authors.lastname: Hung
mesh_terms: D000368:Aged; D029481:Bronchitis, Chronic / Q000150:complications / Q000453:epidemiology; D004646:Emphysema / Q000150:complications / Q000453:epidemiology; D005260:Female; D006801:Humans; D008171:Lung Diseases / Q000150:complications / Q000453:epidemiology; D008175:Lung Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D016239:MEDLINE; D008297:Male; D011014:Pneumonia / Q000150:complications / Q000453:epidemiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000453:epidemiology