title: Association between chronic obstructive pulmonary disease and lung cancer: a case-control study in Southern Chinese and a meta-analysis.
abstract: BACKGROUND
  Lung cancer and chronic obstructive pulmonary disease (COPD) share a common risk factor in cigarette smoking and a large portion of patients with lung cancer suffer from COPD synchronously. We therefore hypothesized that COPD is an independent risk factor for lung cancer. Our aim was to investigate the intrinsic linkage of COPD (or emphysema, chronic bronchitis and asthma) and lung cancer.
  
  
  METHODS
  The present hospital-based case-control study included 1,069 patients with newly diagnosed lung cancer and 1,132 age frequency matched cancer-free controls. The odds ratios (ORs) for the associations between each previous pulmonary disease and lung cancer were estimated with logistic regression models, adjusting for age, sex, family history of cancer, BMI and pack year smoking. In meta-analysis, the pooled effects of previous pulmonary diseases were analyzed with random effects models; and stratification analyses were conducted on smoking status and ethnicity.
  
  
  RESULTS
  In the case-control study, previous COPD was associated with the odds for increased risk of lung cancer (OR = 1.29, 95% confidence interval [CI] = 1.00∼1.68); so were emphysema (OR = 1.55, 95%CI = 1.03∼2.32) and chronic bronchitis (OR = 1.22, 95%CI = 0.99∼1.67); while asthma was associated with odds for decreased risk of lung cancer (OR = 0.29, 95%CI = 0.16∼0.53). These associations were more pronounced in smokers (P<.05 for all strata), but not in non-smokers. In meta-analysis, 35 studies (22,010 cases and 44,438 controls) were identified. COPD was significantly associated with the odds for increased risk of lung cancer (pooled OR = 2.76; 95% CI = 1.85-4.11), so were emphysema (OR = 3.02; 95% CI = 2.41-3.79) and chronic bronchitis (OR = 1.88; 95% CI = 1.49-2.36); and these associations were more pronounced in smokers than in non-smokers (P<.001 respectively). No significant association was observed for asthma.
  
  
  CONCLUSIONS
  Previous COPD could increase the risk of lung cancer, especially in smokers.
authors.affiliation: School of Public Health, The Institute for Chemical Carcinogenesis, The State Key Lab of Respiratory Disease, Guangzhou Medical University, Guangdong, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Yang
authors.forename: Linnan
authors.initials: L
authors.lastname: Zou
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Huang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Guo
authors.forename: Mingan
authors.initials: M
authors.lastname: Pan
authors.forename: Yigang
authors.initials: Y
authors.lastname: Tan
authors.forename: Haibo
authors.initials: H
authors.lastname: Zhong
authors.forename: Weidong
authors.initials: W
authors.lastname: Ji
authors.forename: Pixin
authors.initials: P
authors.lastname: Ran
authors.forename: Nanshan
authors.initials: N
authors.lastname: Zhong
authors.forename: Jiachun
authors.initials: J
authors.lastname: Lu
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D005260:Female; D006801:Humans; D008168:Lung / Q000473:pathology*; D008175:Lung Neoplasms / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects