| AsthmaDefinition - A chronic inflammatory disease of airways, characterized by increased responsiveness of the tracheobronchial tree to various stimuli
- Bronchospasm, once thought to be the primary event in asthma, is now recognized as a secondary phenomenon caused by the underlying inflammatory process.
- Manifested physiologically by widespread narrowing of the air passages, and clinically by paroxysms of dyspnea, cough, chest tightness and wheezing
- Episodic disease, with acute exacerbations interspersed with symptom-free periods
- Most attacks are short-lived, lasting minutes to hours, and can be managed relatively easily.
- Less often, patients develop persistent disease necessitating aggressive therapy.
- Status asthmaticus is the most severe form of asthma.
- Severe obstruction persists for days or weeks
- Can be life threatening
 Epidemiology - Prevalence
- Increasing in many parts of the world, but it is unclear whether this is due to an actual increase in incidence or to overall population growth
- Worldwide: 300 million people
- Affluent countries:
- Adults: 10–12%
- Children: 15%
- Developing countries: lower prevalence but may be rising due to increased urbanization
- Incidence in the U.S.
- 10–11 million persons had acute attacks in 1998.
- 13.9 million outpatient visits
- 2 million requests for urgent care
- 423,000 hospitalizations
- Total cost: >$6 billion
- Ethnic distribution
- More prevalent in minorities and inner-city African-American and Hispanic populations
- Age
- All ages affected, but more prevalent in early life
- ~50% of cases develop before 10 years of age.
- Another one-third of cases occur before 40 years of age.
- Sex
- 2:1 male-to-female ratio in childhood
- Sex ratio equalizes by 30 years of age.
Risk Factors - First-degree relative with a history of asthma
- Personal or family history of atopy
- History of multiple respiratory infections during childhood
- Obesity[1]
- Other risk factors that may be implicated
- Breast feeding during infancy appears to reduce risk of childhood asthma.
Etiology - Airway hyperresponsiveness to both specific and nonspecific stimuli is the hallmark of asthma.
- Etiology is unknown, but genetic susceptibility and airway inflammation are believed to play fundamental roles.
- Cells thought to be important in the inflammatory response include mast cells, eosinophils, lymphocytes, and airway epithelial cells.
- Allergic (extrinsic) asthma
- Associated with a personal and/or family history of allergic diseases, such as rhinitis, urticaria, or eczema
- Immunoglobulin E (IgE) mediated
- Precipitants
- Dust mites (often found in pillows, mattresses, carpets and drapes)
- Cockroaches
- Animal dander, especially cats
- Seasonal pollens
- Idiosyncratic (intrinsic) asthma
- No defined immunologic mechanism
- Precipitants
- Upper respiratory infections
- Exercise
- Gastroesophageal reflux (rarely causes asthma symptoms)
- Exposure to cold air
- Tobacco smoke
- Pollutants: ozone, nitrogen dioxide, sulfur dioxide
- Sulfites in food
- Emotional stress
- Pharmacologic agents
- Aspirin
- NSAIDs
- Tartrazine dyes
- β-Adrenergic antagonists
- Dietary factors (controversial)
- Diets low in antioxidants (vitamin A, vitamin C, magnesium, selenium, omega-3 polyunsaturated fats)
- Diets high in sodium, omega-6 polyunsaturated fats
- Occupational asthma can be both allergic and nonallergic, with hundreds of precipitants having been identified.
Associated Conditions | |
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