Asthma is a chronic respiratory disease, influenced by a combination of genetic and environmental factors and can impact patients at different points or throughout their lives.1 It is defined by airway inflammation, hyperactivity and airway obstruction, epithelial remodelling and excess mucus production.2
In 2007, the US National Asthma Education and Prevention Program Expert Panel Report 3 (NAEPPR3) defined asthma as:3
A chronic inflammatory disorder of the airways in which many cells and cellular elements play a role: in particular, mast cells, eosinophils, neutrophils (especially in sudden onset, fatal exacerbations, occupational asthma, and patients who smoke), T cells, macrophages, and epithelial cells.
In susceptible individuals, this inflammation causes recurrent episodes of coughing (particularly at night or early in the morning), wheezing, breathlessness, and chest tightness. These episodes are usually associated with widespread but variable airflow obstruction that is often reversible either spontaneously or with treatment.
Asthma presents in a heterogeneous way but can be categorised into two forms, Type 2 asthma and non-Type 2 asthma.2 Within these two divisions are further subdivisions, known as “phenotypes”.
The heterogeneity of asthma means it can present with a variety of clinical features.4 Symptoms include intermittent shortness of breath, wheeze, coughing and chest tightness.5
Asthma is a chronic respiratory disease characterised by:
More severe forms are characterised by asthma exacerbations where asthma is poorly controlled and manifests in symptoms such as wheezing, sputum creation and coughing, in addition to shortness of breath. The most severe cases of asthma exacerbations can lead to fatal respiratory failure.2
In clinical trials, the Asthma Quality of Life Questionnaire (AQLQ) is a validated instrument measuring functional problems associated with asthmatic individuals.6
The 2019 Global Strategy for Asthma Management and Prevention by the Global Initiative for Asthma (GINA) defined asthma as “a heterogeneous disease, usually characterised by chronic airway inflammation. It is defined by the history of respiratory symptoms such as wheeze, shortness of breath, chest tightness and cough that vary over time and in intensity, together with variable expiratory airflow limitation.”7
Globally, 339 million adults and children suffer with asthma5 and it is the most common chronic childhood disease. Asthma is a public health concern and healthcare burden for countries of all income brackets, is commonly underdiagnosed, and patients are often inadequately treated.1,7
However, accurate assessment on the prevalence of asthma has been hindered by the condition’s heterogeneity1, varying definitions of asthma and methods of data collection, each combining to make data comparison across studies challenging.
While deaths from asthma have been decreasing globally, asthma deaths in the UK have increased more than 20% in the past 5 years. A lack of awareness regarding the severity of asthma, alongside a lack of basic care, are thought to be contributing factors.8
This is not only a public health concern but also a financial burden, as the cost of managing asthma in Europe ranges from €509 to €2,281 per patient, depending on how well the asthma is controlled, and the number and degree of asthma exacerbations.9
An association has been suggested between asthma and several other diseases including allergic rhinitis, GORD and obesity.1,10,11 Consequently, there is an additional burden on healthcare providers because of these comorbidities.
Asthma can be broadly divided into 2 categories, Type 2 asthma and non-Type 2 asthma, both of which can be subdivided into further subtypes: eosinophilic, neutrophilic and allergic.17
Type 2 is a nomenclature characterising a type of asthma that involves the role of Type 2 innate immune cells such as ILC2, in addition to adaptive immune cells such as Th2 cells.17
Type 2 asthma is the most commonly diagnosed form in childhood with non-Type 2 typically associated with a later onset.
Type 2 asthma is associated with Type 2 inflammatory conditions such as atopic dermatitis. In contrast, development of non-Type 2 asthma can be caused by non-immune factors such as smoking and obesity and is characterised by a low Type 2 cytokine expression in the lungs, lower influx of eosinophils in the airways as well as a lack of response to Type 2 asthma medication, such as glucocorticoids and Type 2 inflammation inhibitors.17
Learn about the key drivers of
Type 2 inflammation.
Discover how asthma control goes beyond exacerbation reduction.Get more information
Type 2 inflammation has been associated with several chronic conditions. Find out how they can present additional challenges.Learn about comorbidities
AQLQ, Asthma Quality of Life Questionnaire; BMI, body mass index; DALYs, disability adjusted life years; GINA, Global Initiative for Asthma; GORD, gastro-oesophageal reflux disease; IgE, immunoglobulin E; ILC2, Type 2 innate lymphoid cells; QoL, quality of life; NAEPRR3, National Asthma Education and Prevention Program Expert Panel Report 3; Th2, T helper cell type 2; UK, United Kingdom; US, United States test.References: