Inclusion criteria:  Male or female participants, aged 50-80 years inclusive. A female is eligible only if she is of non-child bearing potential. Body mass index (BMI) less than (<)35. A signed and dated written informed consent is obtained prior to participation.  Additional inclusion criteria for COPD participants:  A Baseline (post-bronchodilator) (FEV1/FVC) ratio <70 percent (%). Clinically stable and has no exacerbations for at least 1 month prior to recruitment. Ever smoker or never smoker.  Additional inclusion criteria for chronic bronchitis participants:  Free from other significant diseases. Baseline post-bronchodilator FEV1/FVC ratio more than (>)70%. Chronic bronchitis is defined as at least 3 months of cough and phlegm in a year in the past 2 years. Clinically stable and has no exacerbations for at least 1 month prior to recruitment. Ever smoker or never smoker  Additional inclusion criteria for healthy participants:  Free from any significant diseases Baseline post-bronchodilator FEV1/FVC ratio >70%. A CAT score <10. Never smoker. Passive smoker is not eligible.  Exclusion criteria:  Having undergone lung surgery. Known respiratory disorders or significant inflammatory disease other than COPD. Serious, uncontrolled disease (including serious psychological disorders) Confirmed cancer, unless participants in remission for more than or equal to (>=)5 years. Participating or plan to participant in any clinical studies where investigational drugs were tested. Unable or unwilling to use required digital devices (sub- cohort only). Have evidence of alcohol or drug abuse. Have received a blood transfusion in the 4 weeks prior to study start. On long-term oral corticosteroids. Unable to walk. Unable to read and understand Mandarin Chinese.  Additional exclusion criteria for COPD participants:  Current primary diagnosis of asthma (participants with a primary diagnosis of COPD but who also had asthma [Asthma COPD overlap {ACO}] could be included). Known disorders other than COPD that may significantly impact clinical assessments  Additional exclusion criteria for chronic bronchitis participants and healthy participants:  Known disorders that may significantly impact clinical assessments. FVC <80% Predicted.