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- A heterogeneous disease characterized as chronic inflammation of the airway; patients present with history of wheeze, shortness of breath (SOB), chest tightness, and cough which varies in time and intensity along with variable expiratory flow (1).
- Common triggers: exercise, allergen-irritant exposure, change in weather, laughter, or viral respiratory infections
- Patient may experience symptoms-free periods alternating with sporadic flare-up (exacerbations).
- Most common asthma phenotypes (1):
- Allergic asthma: present since childhood and has strong family history
- Non-allergic asthma
- Late onset asthma: particularly in females
- Asthma with fixed airflow limitation: due to airway remodeling
- Asthma with obesity
- Four major classifications of asthma severity used primarily to initiate therapy (2,3):
- Intermittent: symptoms ≤2 days/week, nighttime awakenings ≤2 times per month, short-acting β-agonist (SABA) use ≤2 days/week, no interference with normal activity, and normal forced expiratory volume in 1 second (FEV1) between exacerbations with FEV1 (predicted) >80% and FEV1/forced vital capacity (FVC) >80%
- Mild persistent: symptoms >2 days/week but not daily, nighttime awakenings 3 to 4 times per month, SABA use >2 days/week but not daily, minor limitations in normal activity, and FEV1 (predicted) >80% and FEV1/FVC >80%
- Moderate persistent: daily symptoms, nighttime awakenings ≥1 times per week but not nightly, daily use of SABA, some limitation in normal activity, and FEV1 (predicted) 60–80% and FEV1/FVC 75–80%
- Severe persistent: symptoms throughout the day, nighttime awakenings often 7 times per week, SABA use several times a day, extremely limited normal activity, and FEV1 (predicted) <60% and FEV1/FVC <75%
Asthma affects 300 million individuals worldwide.
- 345,000 deaths every year
- Asthma affects 11.1% of children aged 13 to 14 years (2000 to 2003) in United States.
- Asthma prevalence is greater in boys than girls; however, in adult, women are more affected.
- Obesity is associated with increased prevalence and incidence of asthma, especially in woman with abdominal obesity.
Etiology and Pathophysiology
Airway hyperreaction begins with inflammatory cell infiltration and degranulation, subbasement fibrosis, mucus hypersecretion, epithelial injury, significant smooth muscle hypertrophy and hyperreactivity, angiogenesis that then leads to intermittent airflow obstruction due to reversible bronchospasm (3).
- Genetic association with increased interleukin production and airway hyperresponsiveness leading to asthma; genome-wide association studies (GWAS) show genetic predisposition leading to increased production of IgE, which increased chances of developing the disease.
- Variation in genetic coding has also shown the different level of response to treatment, which is a key factor for controlling the disease and to decrease the rate or exacerbation.
- Host factors: genetic predisposition, gender, race, BMI/obesity
- Environmental: viral infections, animal and airborne allergens, tobacco exposure
- Exercise, obesity, and emotional stress
- Aspirin or NSAIDs hypersensitivity or β-blockers
- Food allergies and asthma increased risk for fatal anaphylaxis from those foods (1,2)
Commonly Associated Conditions
- Atopy: eczema, allergic conjunctivitis, allergic rhinitis
- Obesity (associated with higher asthma rates)
- Gastroesophageal reflux disease (GERD)
- Obstructive sleep apnea (OSA)