Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous and multisystemic disease with progressive increasing morbidity and mortality. COPD is now widely accepted as a heterogeneous condition with multiple phenotypes and endotypes.The recognition of COPD phenotypes and endotypes has significantly impacted the management of the disease. Furthermore, treatable traits (TTs) are recognizable phenotypic or endotypic characteristics that can be assessed and successfully targeted by therapy to improve a clinical outcome in a patient with airway disease. The healthcare system in Hong Kong is different from that of other places. Previous studies in Hong Kong only looked at specific endotypes; an example is the eosinophils cut-off to predict COPD exacerbations and the treatment effect of applying interventions to certain phenotypes, e.g. approaching the exacerbation phenotype with a comprehensive care programme. There is not much information on the overall phenotypes, endotypes, and TTs of COPD patients in Hong Kong. The characteristics of the patients would help to further assess whether the multi-TT approach can improve their outcomes. This study aims to assess 1. the phenotypes, endotypes and treatable traits of COPD patients over time 2. Outcome of patients according to their phenotypes, endotypes and treatable traits over a period of 3 years. 4\) Clustering analyses will also be employed to assess groups of patients with similar characteristics and to assess the change in their outcome over time.