A 3 Year Longitudinal Study of the Level of Asthma Control and Treatment of Asthma Patients in Hong Kong

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.