This is a prospective cohort study that aims to determine the current demographics, clinical characteristics, comorbidities, treatment status and exacerbations of asthma patients.

The primary objective of this study is to determine the current demographics, clinical characteristics, comorbidities, treatment status and exacerbations of asthma patients.

The secondary objectives include: (1) to review the current practices of symptom control assessment, (2) to determine the choice of pharmacological regimen, rate of guideline adherence and real-world clinical practice in managing asthma patients, (3) to evaluate the pattern of lung function parameters (spirometry and forced oscillometry technique [FOT]) in adult asthma patients, (4) to evaluate the effect of ageing on the trend of change in lung function parameters (spirometry and FOT) in adult asthma patients, (5) to identify biomarkers that help to categorize different asthma phenotypes and predict subsequent prognosis, (6) to determine the risk factors of uncontrolled asthma and asthma exacerbation, (7) to evaluate the impact of comorbidities on asthma control.

400 out-patient asthma patients are planned to be recruited and they will be followed up for 3 years.

Asthma is a common respiratory disease worldwide and in Hong Kong. According to the estimation by the Center for Disease Control and Prevention in 2015, 7.6% adults in the United States have asthma. In Hong Kong, the prevalence of asthma was estimated to be 10.1% among 13 to 14 years old children and 5.8% in randomly selected Chinese elderly aged more than 70. With a rising trend of life expectancy in Hong Kong, the epidemiology of asthma in adult and elderly population may change over time. In addition, elderly patients with asthma may present with a different spectrum of clinical characteristics and pharmacological response.

Asthmatic exacerbation is one of the untoward complications and hospitalization for exacerbations requiring ICU care and mechanical ventilation are both predictors for near-fatal asthma. After the acute attack, its unfavourable impact continues and can lead to multiple sequelae. Exacerbation of asthma is associated with a more rapid decline in the post-bronchodilator forced expiratory volume in 1 second and worse quality of life. Without adjustment of medical treatment, they are prone to develop another episode of exacerbation within a short period of time. In addition, individuals with uncontrolled asthma had higher medical expenditures and decreased productivity, contributing to a greater economic burden when compared with individuals without asthma. In contrary, patients with controlled asthma had lower hospitalization rate, mortality rate and less lung function decline. Many risk factors for exacerbation had been identified including upper airway diseases, gastroesophageal reflux, poor inhaler technique, medication non-compliance. Many of these factors are potentially reversible. A model of better asthma care may be established by improving the understanding on these risk factors, leading to less exacerbation events.

Asthma is not simply an airway disease. Accumulating evidence showed its coexistence with other upper airway and systemic diseases, both atopic and non-atopic. These comorbidities independently or linked together to impose negative impact on patients' health status and quality of life. Knowing about the burden of asthma related comorbidities may help to guide clinician in managing these complications in a more effective way, and even prediction of subsequent prognosis.

Since the launching of GINA guideline in year 1993, its regular evidence-based update on pharmacological treatment had revolutionize the care of asthma patients. The use of asthma medications by both specialists and primary care physicians became more structured and the asthma control was improved. However, there is still a significant proportion of asthma patients experiencing recurrent exacerbation despite optimization of pharmacological treatment. Both the guideline adherence by physicians and drug compliance by patient are subjects of concern.

Previous evidence showed that the compliance rate of GINA guideline is far from satisfactory, which is a shared phenomenon among different common diseases even the presence of well-established international guideline. Patient's drug compliance also contributes to negative disease outcome, especially non-adherence to inhaled corticosteroid. Currently, a comprehensive view on the treatment status in and level of asthma control in Hong Kong is still lacking.

A large knowledge gap exists between the current demographics, comorbidities, treatment status, level of asthma control and exacerbations in Hong Kong. An updated study on these aspects is definitely warranted to enhance patient care and guide further research.

Inclusion Criteria:

1. All patients with confirmed diagnosis of asthma (defined as those with a consistent history and prior documented evidence of variable airflow obstruction, with evidence of an increase in FEV1 greater than 12% or 200 mL following bronchodilator or bronchial hyperresponsiveness on bronchial provocation testing, when stable (reference)
2. Age greater than 18 years old
3. Signed written informed consent to participate in the study

Exclusion Criteria:

1. Patients currently with acute exacerbation of asthma by GINA guideline (they can join the study after 6 weeks post recovery from the exacerbation)
2. Patients with respiratory diseases that can show similar symptoms to asthma such as bronchiectasis, tuberculosis-destroyed lung parenchyma, endobronchial TB, and lung cancer, or those who have history of these diseases based on physician's judgment
3. Patients with respiratory diseases that may confound the lung function parameters such as pleural diseases, interstitial lung diseases, and previous lung surgery, or those who have history of these diseases based on physician's judgment
4. Patients with neuromuscular diseases that may affect the seal off the mouthpiece during spirometry and forced oscillometry technique (FOT)
5. Patients with uncontrolled or active contagious respiratory infection diseases
6. Patients with smoking history more than 10 pack years
7. Significant comorbid illnesses that limit the life expectancy to less than 1 year
8. Patients who are mentally not fit or physically contraindicated for spirometry and FOT
9. Patients with psychiatric disease or cognitive impairment that may limit their ability of understanding or giving consent to the study
10. Patients currently randomized in other clinical studies

Patients are recruited from the medical out-patient clinic by the physicians in the Prince of Wales Hospital. As the physicians will both attend general medical clinics and respiratory clinics, they will recruit patients from these clinics

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Starting 6 months after publication

upon individual approach for metaanalysis or related study