title: Better understanding the influence of cigarette smoking and indoor air pollution on chronic obstructive pulmonary disease: a case-control study in Mainland China.
abstract: OBJECTIVE
  Although the association between COPD and smoking status (non-smoking, ex-smoking and current smoking) and indoor air pollution in Chinese populations is well established, the link between COPD and the number of cigarettes smoked has not been examined. This study investigated the relationship between the total amount of cigarettes smoked (TACS) and indoor air pollution, with the risk of COPD among urban and rural Chinese adults.
  
  
  METHODS
  A nested case-control study was performed using data collected in a large community survey (N = 29 319) conducted between October 2000 and March 2001 in Nanjing, China. The exposure to indoor respiratory pollutants of cooking and heating materials and to passive cigarette smoke was compared in patients diagnosed with COPD (n = 1743) and controls matched for age, gender and residence (n = 1743).
  
  
  RESULTS
  The smoking rate among COPD patients was significantly higher than that among the controls. After controlling for possible confounders, the adjusted odds ratios for COPD increased across TACS tertiles: from lower (OR = 1.40, 95% confidence interval (CI): 1.09-1.79), to middle (OR = 1.55, 95% CI: 1.21-1.99), and upper (OR = 1.77, 95% CI: 1.37-2.29). Among smokers, women were significantly more likely to develop COPD than men (OR = 1.20, 95% CI: 1.02-1.41). There were no significant associations between COPD and domestic fuels used, kitchen ventilation or passive smoking. Heating in winter with coal was weakly but positively linked with COPD among non-smokers overall, among women non-smokers, and specifically for women living in urban as well as rural areas.
  
  
  CONCLUSIONS
  A clear dose-response relationship exists between cigarette smoking and COPD; compared with men, women smokers were more susceptible to COPD. Exposure to other respiratory pollutants in the home was not significantly associated with the diagnosis of COPD.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Nanjing Medical University, Nanjing, China. f_xufei@hotmail.com
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.forename: XiaoMei
authors.initials: X
authors.lastname: Yin
authors.forename: HongBing
authors.initials: H
authors.lastname: Shen
authors.forename: YaoChu
authors.initials: Y
authors.lastname: Xu
authors.forename: Robert S
authors.initials: RS
authors.lastname: Ware
authors.forename: Neville
authors.initials: N
authors.lastname: Owen
mesh_terms: D000328:Adult; D000368:Aged; D016902:Air Pollution, Indoor / Q000706:statistics & numerical data*; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D005260:Female; D006361:Heating; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D014691:Ventilation