title: Improvement in household stoves and risk of chronic obstructive pulmonary disease in Xuanwei, China: retrospective cohort study.
abstract: OBJECTIVE
  To test whether improvement in household coal stoves affected the incidence of chronic obstructive pulmonary disease (COPD) in Xuanwei County, China.
  
  
  METHODS
  Retrospective cohort study (follow-up 1976-92) comparing incidence of COPD between groups with and without chimneys.
  
  
  METHODS
  20,453 people born into homes with unvented coal stoves;16,606 (81.2%) subsequently changed to stoves with chimneys.
  
  
  METHODS
  Installation of a chimney in households in which unvented stoves had been used previously.
  
  
  RESULTS
  Installation of a chimney was associated with distinct reduction in the incidence of COPD. Compared with people who did not have chimneys, the Cox-modelled risk ratio (relative risk) was 0.58 (95% confidence interval 0.49 to 0.70, P < 0.001) in men and 0.75 (0.62 to 0.92, P = 0.005) in women. Modelled risk ratios were robust to different Cox model specifications. Relative risks decreased with time since stove improvement. In both sexes, the reduction in risk became unequivocal about 10 years after stove improvement.
  
  
  CONCLUSIONS
  In Xuanwei, incidence of COPD decreased markedly after household coal stoves were improved.
authors.affiliation: College of Public Health, Chulalongkorn University, Institute Building 3, 10th Floor, Soi Chulalongkorn 62, Phyathai Road, Patumwan, Bangkok 10330, Thailand.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Chapman
authors.forename: Xingzhou
authors.initials: X
authors.lastname: He
authors.forename: Aaron E
authors.initials: AE
authors.lastname: Blair
authors.forename: Qing
authors.initials: Q
authors.lastname: Lan
mesh_terms: D016902:Air Pollution, Indoor / Q000009:adverse effects; D002681:China / Q000453:epidemiology; D003031:Coal / Q000009:adverse effects / Q000706:statistics & numerical data; D003296:Cooking / Q000706:statistics & numerical data*; D004812:Epidemiologic Methods; D005260:Female; D006794:Household Articles / Q000706:statistics & numerical data*; D006798:Housing / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D012307:Risk Factors
chemical_list: D003031:Coal