Is Previous Respiratory Disease a Risk Factor for Lung Cancer?

Rationale: Previous respiratory diseases have been associated with increased risk of lung cancer. Respiratory conditions often co-occur and few studies have investigated multiple conditions simultaneously. Objectives: Investigate lung cancer risk associated with chronic bronchitis, emphysema, tuberculosis, pneumonia and asthma. Methods and Measurements: The SYNERGY project pooled information on previous respiratory diseases from 12,739 cases and 14,945 controls from 7 case-control studies conducted in Europe and Canada. Multivariate logistic regression models were used to investigate the relationship between individual diseases adjusting for co-occurring conditions, and patterns of respiratory disease diagnoses and lung cancer. Analyses were stratified by sex, and adjusted for age, centre, ever-employed in a high-risk occupation, education, smoking status, cigarette pack-years and time-since quitting smoking. Main Results: Chronic bronchitis and emphysema were positively associated with lung cancer, after accounting for other respiratory diseases and smoking (for example in men OR=1.33; 95% CI 1.20-1.48 and 1.50; 1.21-1.87, respectively). A positive relationship was observed between lung cancer and pneumonia diagnosed 2 or fewer years prior to lung cancer (OR=3.31; 2.33-4.70 for men), but not longer. Co-occurrence of chronic bronchitis, emphysema and pneumonia had a stronger positive association with lung cancer than individual conditions. Asthma had an inverse association with lung cancer, the association being stronger with an asthma diagnosis 5 or more years prior to lung cancer compared to shorter. Conclusions: Findings from this large international case-control consortium indicate that after accounting for co-occurring respiratory diseases, chronic bronchitis and emphysema continue to have a positive association with lung cancer.