TABLE 1

Inclusion criteria

	COPD participants	Chronic bronchitis participants	Healthy 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 years	✓	N/A	N/A
60 COPD participants without inhaler maintenance treatment history for ≥12 months prior to the entry of the study	✓	N/A	N/A

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