Prior tuberculosis, smoking and airflow obstruction: a cross-sectional analysis of the Guangzhou Biobank Cohort Study

BACKGROUND: Prior pulmonary tuberculosis (TB) has been shown to be associated with higher risk of airflow obstruction, the hallmark of chronic obstructive pulmonary disease (COPD), but whether smoking modifies this relationship is unclear. We investigated the relationships between prior TB, smoking and airflow obstruction in a Chinese population sample. METHODS: Participants in the Guangzhou Biobank Cohort Study underwent spirometry, chest radiography and a structured interview on lifestyle and exposures. Prior TB was defined as the presence of radiographic evidence suggestive of inactive TB. Airflow obstruction was based on spirometric criteria. RESULTS: The prevalence of prior TB in this sample (N=8,066, mean age: 61.9 years) was 24.2%. After controlling for sex, age, and smoking exposure, prior TB remained independently associated with increased risk of airflow obstruction (OR=1.37; 95% CI 1.13-1.67). Further adjustment for exposure to passive smoking, biomass fuel and dust did not alter the relationship. Smoking did not modify the relationship between prior TB and airflow obstruction. CONCLUSIONS: Prior TB is an independent risk factor for airflow obstruction, which may partly explain the higher prevalence of COPD in China. Clinicians should be aware of this long term risk in individuals with prior TB, irrespective of smoking status, particularly in patients from countries with high TB burden.