Asthma
Chronic airway inflammation with variable symptoms and airflow obstruction.
Asthma is a common long-term inflammatory disease of the airways characterized by variable and recurring symptoms and reduced lung function. It is notable as a widespread condition affecting hundreds of millions of people worldwide, with no known cure but manageable through various treatments including inhaled corticosteroids.
Quick Facts
- Field
- Pulmonology
- Symptoms
- Recurring episodes of wheezing
- coughing
- chest tightness
- shortness of breath
- Complications
- Gastroesophageal reflux disease (GERD)
- sinusitis
- obstructive sleep apnea
- Onset
- Childhood
- Duration
- Long term
- Causes
- Genetic and environmental factors
- Risks
- Air pollution
- allergens
- urban environments
- Diagnosis
- Based on symptoms and spirometry
Facts from the source article.
Classification
Asthma is often considered a syndrome rather than a single condition due to diversity in onset, symptoms, outcomes, and treatment response. Historically classified as extrinsic (caused by external factors such as allergens) or intrinsic (unrelated to allergies), asthma is now most commonly classified according to severity, control of symptoms, phenotypes, and endotypes. Asthma and chronic obstructive pulmonary disease (COPD) both cause airway restriction, but in asthma expiratory airflow fluctuates over time, whereas in COPD airflow obstruction is chronic and often worsens over time. Asthma severity is determined by how much medication is required to control symptoms and exacerbations, while asthma control assesses the burden of symptoms and inflammation without depending on medication usage. Control is evaluated through symptom frequency and severity, impairment, rescue inhaler use, questionnaires, healthcare usage, and objective tests such as spirometry, FeNO, sputum eosinophils, and hyperresponsiveness studies. Severity can only be measured once the disorder is under control; mild asthma may require only as-needed medication, while severe asthma requires high doses or remains uncontrolled. Phenotypes describe how the condition presents, and endotypes describe underlying mechanisms. Asthma is divided into two main endotypes: T2-high and T2-low (non-T2), with subpopulations that may overlap.
Causes
Asthma results from a mixture of genetic and external factors, manifesting when genetic susceptibility is combined with specific environmental exposures. Factors during pregnancy linked to asthma development include maternal weight gain or obesity, stressful pregnancy, smoking while pregnant, certain medications, and caesarean section. Early childhood exposure to secondhand smoke, high parental stress, respiratory infections, and indoor mold or fungi are also associated. Prenatal or childhood cigarette smoke exposure increases asthma likelihood, and maternal grandmother smoking during pregnancy raises risk regardless of the mother's asthma or smoking status; nicotine is believed responsible, linked to DNA changes. Respiratory tract infections, especially severe or recurring ones in early childhood, can decrease lung function and lead to asthma, though some infections may lessen risk (the hygiene hypothesis). Chronic exposure to outdoor air pollution (nitrogen dioxide, traffic pollution) and indoor pollution (biomass, pesticides, building materials, mold, dust mites, cockroaches, endotoxins) increases asthma risk. Asthma is more common in urban than rural environments, attributed to higher risk factors in urban settings and protective factors in rural ones.
Diagnosis
Diagnostic guidelines for asthma vary regarding testing methods, timing, and criteria; no single test confirms the diagnosis, which is based on a combination of symptoms and respiratory function testing. Guidelines advise objective tests for people with suggestive symptoms, including spirometry, bronchodilator reversibility (BDR) testing, and peak flow variability. Characteristic symptoms include wheezing, shortness of breath, chest tightness, and coughing that fluctuate with time of day and triggers. Personal or family history of allergic conditions can help identify asthma. Physical findings are rare unless the person is symptomatic; if someone is unwell or highly symptomatic, guidelines recommend treating before testing. For children above five and adults, GINA guidelines suggest confirming variable expiratory airflow in those with suggestive symptoms, using spirometry, peak expiratory flow, or bronchial provocation testing. Spirometry measures how much air a person can forcefully exhale in one second (FEV1) compared to total exhaled air (FEV1/FVC ratio); testing is performed before and after medication, with an increase in FEV1 after medication indicating asthma. If spirometry is unavailable, peak expiratory flow measured twice daily for two weeks showing daily changes greater than 10% may suggest asthma.
Management
The goal of asthma management is to reduce symptoms and minimize risks of complications such as exacerbations, reduced lung function, and medication side effects. This involves evaluating asthma control and exacerbation risk, providing education and guidance, identifying and minimizing triggers, and using medication. Asthma control should be reviewed during appointments to adjust treatment. After diagnosis, the person and family should receive education about the disease and a management plan, including trigger avoidance, self-monitoring of symptoms or peak expiratory flow, an asthma action plan, and treatment options. School-based education programs decrease hospitalizations in school-aged children. Non-medical strategies include avoiding cigarette smoke (both smoking and secondhand smoke) and, for occupational asthma, avoiding workplace sensitizers and allergens. Guidelines do not recommend avoiding all indoor or outdoor allergens due to the variety and difficulty of elimination. Certain medications (aspirin, beta-blockers, NSAIDs) can worsen symptoms in some individuals but are considered safe unless they have caused past adverse reactions.
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