Inclusion criteria

COPD participantsChronic bronchitis participantsHealthy participants
Inclusion criteria (all the following criteria apply)
 Aged 50–80 years inclusive
 Baseline (post-bronchodilator) FEV1/FVC ratio<70%≥70%≥70%
 CAT score <10
 BMI <35 (for CT scanning reasons)
 Chronic mucus hypersecretion (≥3 months of cough and phlegm in a year in the past 2 years)
 No exacerbations for ≥1 month prior to recruitment
 Ever-smoker (lifetime exposure of ≥1 pack-year) or never-smoker (lifetime exposure of <1 pack-year) (for healthy participants, ever-smokers and passive smokers are not eligible)
Additional criteria for sub-cohort of COPD participants
 150 COPD participants with ≥1 moderate or severe exacerbation event within the past 2 yearsN/AN/A
 60 COPD participants without inhaler maintenance treatment history for ≥12 months prior to the entry of the studyN/AN/A

FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; CAT: COPD Assessment Test; BMI: body mass index.