Asthma

Descriptive text is not available for this imageBASICS

DESCRIPTION

  • Asthma is a chronic condition characterized by reversible bronchoconstriction/hyperresponsiveness of the airways, often with the presence of airway inflammation.
  • Diagnosis (Look for the three Rs.)
    • Recurrence: repeated episodes of cough, wheeze, or shortness of breath
    • Reactivity: Symptoms are brought on by a specific occurrence or exposure (trigger).
    • Responsiveness: Symptoms diminish in response to bronchodilator or anti-inflammatory agent.

EPIDEMIOLOGY

  • 6 million children are currently living with asthma in the United States.
  • 1 out of 10 school-aged children has asthma, making it one of the most common chronic illnesses among children.
  • The greatest burden of asthma falls disproportionately on children of racial/ethnic minority groups and those living below the national poverty line.
  • The incidence of asthma decreases with age and is 5 times higher in younger children (age 0 to 4 years) than older children (age 5 to 17 years).
  • Most adolescents who wheeze will have asthma that persists into adulthood, especially if comorbidities are present.
  • Impact
    • Asthma is common and costly, with an estimated annual loss of $82 billion due to mortality, medical care, and lost work.
    • Asthma accounts for 25% of all emergency department visits annually and is the 3rd highest cause of hospitalization in children aged <15 years.
  • Disparities
    • Morbidity and mortality are disproportionately higher among low-income, inner-city children, likely due to a combination of structural and social inequities.
    • Children living in low-income communities and communities of color are more likely to be exposed to both indoor and outdoor triggers including mold, pests, air pollution, and particulate matter, leaving these groups at higher risk of poor asthma-related outcomes.
    • Despite advances in policy and research, there are persistent gaps in asthma outcomes between Black, Hispanic, and indigenous children compared to White children in the United States.
      • Black and Puerto Rican children are nearly 3 times more likely to be hospitalized or die from asthma.
      • Black and Hispanic children have been found less likely to be prescribed appropriate asthma medications for preventive care or acute exacerbations.
      • Higher asthma prevalence is noted among American Indian/Alaska Native children who are also twice as likely to experience daily symptoms.
  • Mortality
    • Death from asthma may occur in asthma of any severity, including intermittent asthma, but is more likely when symptoms are poorly recognized and undercontrolled.
    • Overall, death from asthma in children has steadily decreased in recent decades due partly to better recognition and increased use of effective preventive medications.

RISK FACTORS

  • Complex interactions between biologic and environmental factors can increase susceptibility to asthma.
    • Family history of asthma
    • Prematurity
    • Allergic rhinitis and atopic dermatitis
    • Obesity/overweight
    • Tobacco smoke exposure
    • Exposure to inhaled indoor/outdoor allergens, chemicals, or pollutants
    • Severe respiratory syncytial virus (RSV)/rhinovirus infection or hospitalization for bronchiolitis
  • Genetics
    • Asthma is a heterogenous condition; identification of phenotype may help stratify asthma subgroups and better predict individual clinical response to therapy.
    • Studies suggest that epigenetics may have a role in the pathogenesis of asthma via mechanisms such as DNA methylation (reversible DNA modification in response to environmental influence).
    • Emerging research identifies genetic polymorphisms that may help explain certain ethnic disparities in outcomes as well as variations in asthma susceptibility, severity, and response to medications.

GENERAL PREVENTION

  • Currently, there are no established methods for primary prevention of asthma, although reduced exposure to tobacco smoke is recommended.
  • Farm residence, cohabitation with dogs, birth by vaginal delivery, and breastfeeding could confer some protection due to alteration of the developing microbiome in young children; studies are limited.
  • Once asthma is diagnosed, aim to prevent severe exacerbations and lost work/school days as well as comorbidities such as obesity and depression.
  • Effective measures (see “Patient Education” section) include the following:
    • Supported adherence to environmental, behavioral, and medical treatment plan
    • Written asthma action plan: shown to reduce emergency department visits and lost school/work days
    • Education about and avoidance of triggers
  • In addition to standard recommended vaccines, children with asthma should receive seasonal vaccines such as influenza and COVID-19.

PATHOPHYSIOLOGY

  • Immune and inflammatory responses in the airways are triggered by an array of environmental antigens, irritants, or infectious organisms.
  • Airway is stimulated and primary inflammatory mediators released.
  • Airway is invaded by inflammatory cells (mast cells, basophils, eosinophils, macrophages, neutrophils, B and T lymphocytes).
  • Inflammatory cells respond to and produce various mediators (cytokines, leukotrienes, lymphokines), augmenting the inflammatory response.
  • Airway epithelium is inflamed and becomes disrupted, and basal membrane is thickened.
  • Airway smooth muscle is hyperresponsive, and bronchoconstriction ensues.
  • Eosinophilia and the ability to make excess immunoglobulin E (IgE) in response to antigen are associated with increased airway reactivity.
  • Viral infections, particularly RSV during infancy, may play a role in the development of asthma or may modify the severity of asthma.
  • Airway smooth muscle hypertrophy and airway epithelial hyperplasia are characteristic chronic changes resulting from poorly controlled asthma.

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