Previous pulmonary diseases and risk of lung cancer in Gansu Province, China

Backgrounds Although active smoking is well established as the main cause o f lung cancer, there is accumulating evidence that history of prior lung di seases may be an independent risk factor for lung cancer. Methods A population-based case-control study in Gansu Province, China iden tified 886 lung cancer cases (656 male, 230 female) diagnosed between Janua ry 1994 and April 1998. A standardized interview collected information on a variety of potential risk factors including a history of physician-diagnos ed non-malignant lung diseases (pulmonary tuberculosis, chronic bronchitis/ emphysema, asthma, pneumonia), age and year in which each condition was fir st diagnosed, and any therapy or hospitalization received. Results Pulmonary tuberculosis (odds ratio [OR] = 2.1, 95% CI:1.4-3.1) and chronic bronchitis/emphysema (OR = 1.4 95% CI : 1.1-1.8) were associated wi th increased risk of lung cancer, after adjustment for active smoking and s ocioeconomic status. The OR for asthma (OR = 1.4, 95% CI : 0.9-2.1) and pne umonia (OR = 1.5, 95% CI: 1.0-2.3) were also elevated. The risk of lung can cer remained significant for pulmonary tuberculosis and chronic bronchitis/ emphysema when analysis was limited to the pathologically confirmed cases a nd self-responders. Conclusions This study provides additional evidence that previous pulmonary tuberculosis and chronic bronchitis/emphysema are causally related to lung cancer, although the precise mechanism is still unclear. The results for a sthma and pneumonia, while suggestive of a positive association, did not re ach the traditional level of statistical significance and should be interpr eted with caution.