Chronic bronchitis worsens all measured outcomes in mild–moderate COPD

Objectives Chronic bronchitis in COPD is associated with worse outcomes. Previous studies were performed in patients with severe airflow limitation; less is known about its impact in milder disease. Methods Data are from the COMPASS cohort study. Patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) I and II COPD were categorised into the presence (CB+) or absence (CB−) of chronic bronchitis. Clinical characteristics were assessed in all patients; quantitative computed tomography (CT) and sputum microbiome were analysed in a subset of the main cohort. Differences between groups were compared using ANCOVA and generalised linear models. Results 1375 COPD patients were included: 88.7% male, mean age 65.0 years, mean post-FEV 1 74.8% pred. Prevalence of CB+ was 63.7%. CB+ patients had a higher annualised rate of moderate or severe exacerbations (rate ratio 2.24, 95% CI 1.64–3.06). Overall, CB+ patients had worse post-bronchodilator forced expiratory volume in 1 s (72.6% pred versus 76.0% pred, p<0.001). COPD Assessment Test and St George's Respiratory Questionnaire scores were higher in the CB+ cohort by more than their minimal clinically important differences. Notably, CB+ patients in GOLD I had more exacerbations and worse health status than CB− patients in GOLD II. On quantitative CT scan, CB+ had a higher expiratory/inspiratory ratio and more evidence of functional small airways disease. Sputum microbiome in CB+ showed significantly increased relative abundances of Streptococcus and Pseudomonas . Conclusion The presence of chronic bronchitis in mild–moderate airflow limitation was associated with significantly greater severity in every clinical domain. Mechanisms may include gas-trapping due to small airways disease and its resulting overinflation, together with changes in airway microbiome.