Asthma

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Basics

Description

  • A heterogeneous disease characterized as chronic inflammation of the airway (1)
  • Common triggers: exercise, allergen-irritant exposure, change in weather, laughter, or viral respiratory infections
  • Patient may experience symptom-free periods alternating with sporadic flare-up (exacerbations).
  • Most common asthma phenotypes:
    • Allergic asthma: usually present since childhood and has strong family history of allergic diseases
    • Nonallergic asthma
    • Late-onset asthma: more common in females
    • Asthma with fixed airflow limitation: due to airway remodeling
    • Asthma with obesity
  • Asthma severity is assessed retrospectively from treatment required to control symptoms.
    • Mild asthma: well controlled with Step 1 or 2 treatment (i.e., with as-needed ICS-formoterol alone or with low-intensity maintenance controller treatment)
    • Moderate asthma: well controlled with Step 3 or 4 treatment (i.e., low- or medium-dose ICS-LABA
    • Severe asthma: remains “uncontrolled” with optimized treatment with high-dose ICS-LABA or that requires high-dose ICS-LABA to prevent it from becoming “uncontrolled”

Epidemiology

Incidence
Traffic-related air pollution may be attributable to 13% of global asthma incidence.

Prevalence
Asthma affects 235 million individuals worldwide.

  • 490,000 deaths worldwide reported in 2017
  • Asthma affects about 10% of children ages 5 to 18 years in the United States.
  • Asthma prevalence is greater in boys than girls; however, in adults, women are more affected.
  • Obesity is associated with increased prevalence and incidence of asthma.
  • Rate of asthma deaths largest among those aged >65

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.

Genetics
Genetic association with increased interleukin (IL) or IgE production and airway hyperresponsiveness leading to asthma

Risk Factors

  • Host factors: genetic predisposition, sex, race, obesity, preterm, or small for gestational age (SGA)
  • Environmental: viral infections, animal and airborne allergens, tobacco smoke exposure, pollution, stress
  • Aspirin or NSAIDs hypersensitivity
  • Persons with food allergies and asthma are at increased risk for fatal anaphylaxis from those foods.

Commonly Associated Conditions

  • Atopy: eczema, allergic conjunctivitis, allergic rhinitis
  • Obesity (associated with higher asthma rates)
  • Gastroesophageal reflux disease (GERD)
  • Obstructive sleep apnea (OSA)

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Basics

Description

  • A heterogeneous disease characterized as chronic inflammation of the airway (1)
  • Common triggers: exercise, allergen-irritant exposure, change in weather, laughter, or viral respiratory infections
  • Patient may experience symptom-free periods alternating with sporadic flare-up (exacerbations).
  • Most common asthma phenotypes:
    • Allergic asthma: usually present since childhood and has strong family history of allergic diseases
    • Nonallergic asthma
    • Late-onset asthma: more common in females
    • Asthma with fixed airflow limitation: due to airway remodeling
    • Asthma with obesity
  • Asthma severity is assessed retrospectively from treatment required to control symptoms.
    • Mild asthma: well controlled with Step 1 or 2 treatment (i.e., with as-needed ICS-formoterol alone or with low-intensity maintenance controller treatment)
    • Moderate asthma: well controlled with Step 3 or 4 treatment (i.e., low- or medium-dose ICS-LABA
    • Severe asthma: remains “uncontrolled” with optimized treatment with high-dose ICS-LABA or that requires high-dose ICS-LABA to prevent it from becoming “uncontrolled”

Epidemiology

Incidence
Traffic-related air pollution may be attributable to 13% of global asthma incidence.

Prevalence
Asthma affects 235 million individuals worldwide.

  • 490,000 deaths worldwide reported in 2017
  • Asthma affects about 10% of children ages 5 to 18 years in the United States.
  • Asthma prevalence is greater in boys than girls; however, in adults, women are more affected.
  • Obesity is associated with increased prevalence and incidence of asthma.
  • Rate of asthma deaths largest among those aged >65

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.

Genetics
Genetic association with increased interleukin (IL) or IgE production and airway hyperresponsiveness leading to asthma

Risk Factors

  • Host factors: genetic predisposition, sex, race, obesity, preterm, or small for gestational age (SGA)
  • Environmental: viral infections, animal and airborne allergens, tobacco smoke exposure, pollution, stress
  • Aspirin or NSAIDs hypersensitivity
  • Persons with food allergies and asthma are at increased risk for fatal anaphylaxis from those foods.

Commonly Associated Conditions

  • Atopy: eczema, allergic conjunctivitis, allergic rhinitis
  • Obesity (associated with higher asthma rates)
  • Gastroesophageal reflux disease (GERD)
  • Obstructive sleep apnea (OSA)

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