Relation between duration of smoking cessation and bronchial inflammation in COPD

Abstract

Background: Chronic obstructive pulmonary disease (COPD) is associated with airway inflammation. Although smoking cessation improves symptoms and the decline in lung function in COPD, it is unknown whether bronchial inflammation in patients with established COPD varies with the duration of smoking cessation. Methods: 114 patients (99 men) with COPD of mean (SD) age 62 (8) years, a median (IQR) smoking history of 42 (31–55) pack years, no inhaled or oral corticosteroids, all current or ex-smokers (n = 42, quit >1 month, median cessation duration 3.5 years), post-bronchodilator FEV₁ 63 (9)% predicted, and FEV₁/IVC 48 (9)% were studied cross sectionally. The numbers of subepithelial T lymphocytes (CD3, CD4, CD8), neutrophils, macrophages, eosinophils, mast cells, and plasma cells were measured in bronchial biopsy specimens (median (IQR)/0.1 mm²) using fully automated image analysis. Results: Ex-smokers with COPD had higher CD3+, CD4+, and plasma cell numbers than current smokers with COPD (149 (88–225) v 108 (61–164), p = 0.036; 58 (32–90) v 40 (25–66), p = 0.023; and 9.0 (5.5–20) v 7.5 (3.1–14), p = 0.044, respectively), but no difference in other inflammatory cells. Short term ex-smokers (Conclusions: With longer duration of smoking cessation, CD8 cell numbers decrease and plasma cell numbers increase. This indicates that bronchial T lymphocyte and plasma cell counts, but not other inflammatory cells, are related to duration of smoking cessation in patients with COPD.