We searched for English language articles and reviews in PubMed and Cochrane published between inception and Oct 1, 2017. The search combined the terms “Asthma” and the subheadings “epidemiology”, “aetiology”, “exacerbations”, “pathophysiology”, “innate AND adaptive immunity”, “diagnosis”, “therapeutics”, and “prevention”. We prioritised papers published from 2013 onwards. We also searched the reference lists of articles identified by this search and selected those we deemed most relevant.
SeminarAsthma
Section snippets
Epidemiology
Asthma is one of the most common chronic, non-communicable diseases, and affects around 334 million people worldwide.1 The global prevalence of self-reported, doctor-diagnosed asthma in adults is 4·3% (95% CI 4·2–4·4), with wide variation between countries. Prevalence is highest in developed countries—eg, Australia (21·0%)2—and lowest in developing countries—eg, China (0·2%).2 Greater variation is seen for asthma symptoms in children, ranging from 2·8% (Indonesia) to 37·6% (Costa Rica) in
Pathogenesis of asthma
Asthma is a heterogeneous condition in both children and adults. Dissecting this heterogeneity is contributing to our understanding of disease pathogenesis and development of new therapeutic strategies, especially in severe disease. The observable characteristics (phenotype) of asthma—including clinical features of the disease and their underlying mechanisms (endotype)—are complex and represent a multitude of host–environment interactions that occur over different spatial scales (ie, genes to
Definition and clinical presentation
Asthma is a heterogeneous condition characterised by variable respiratory symptoms and variable airflow limitation. These features can be generated by a range of underlying mechanisms that are typically, but not always, associated with airway inflammation and airway remodelling.
Diagnosis of asthma
No gold standard exists for diagnosis of asthma. Diagnosis is probability-based, and considers symptoms and variable expiratory airflow limitation. Asthma is heterogeneous, and for some patients, one or both of these features might not be found.
Many features can increase or decrease the probability that symptoms are due to asthma (appendix). In children, accurate assessment of symptoms and rescue β2 agonist use can be difficult, because most information is given by the parents, who are not
Long-term management
Asthma treatment goals in children and adults are to minimise both the symptom burden (day-to-day symptoms, disturbed sleep, and activity limitation) and the risk of adverse asthma outcomes (exacerbations, persistent airflow limitation, and medication side-effects). Together, these two domains constitute asthma control. For many patients, these goals can be achieved with current treatment approaches. Patients' personal goals might differ from these medical goals, so the clinician should ask
Severe asthma
Severe asthma is defined in the European Respiratory Society and American Thoracic Society guidelines for adults and children aged at least 6 years as asthma that requires treatment with guidelines-suggested medication for GINA steps 4–544 for the past year, or systemic corticosteroids for at least 50% of the past year, to prevent it from becoming uncontrolled, or which remains uncontrolled despite therapy.50 Uncontrolled asthma refers to poor symptom control, frequent severe exacerbations,
Asthma exacerbations
Acute or subacute episodes of increased symptoms—known as exacerbations, asthma attacks, or flare-ups—punctuate the natural course of asthma and require a change in treatment. Exacerbations are characterised by progressively increasing shortness of breath, cough, wheezing or chest tightness, and decreasing lung function. Onset is usually rapid in children, but can develop over a week or more in adults. Exacerbations account for a substantial portion of asthma-related expenditure; they affect
Search strategy and selection criteria
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