Is there a type of asthma that occurs with physical exertion?

Exercise-Induced Bronchoconstriction: A Type of Asthma Triggered by Physical Activity

Exercise-induced bronchoconstriction (EIB) is the preferred term for the transient narrowing of the lower airway that occurs after exercise, which can affect individuals with or without underlying asthma. 1, 2

Definition and Pathophysiology

• EIB is characterized by airway narrowing that occurs during or after physical exertion, not a separate type of asthma but rather a trigger for bronchoconstriction 2
• The term "exercise-induced bronchoconstriction" is preferred over "exercise-induced asthma" (EIA) as it doesn't imply that exercise causes asthma but rather triggers or exacerbates symptoms 1
• EIB is triggered by the loss of water in bringing large volumes of air to body conditions in a short time during exercise 1
• The mechanisms involve thermal (cooling and rewarming) and/or osmotic effects of airway dehydration 1
• Increased osmolarity stimulates mast cell degranulation, leading to the release of inflammatory mediators such as histamine, tryptase, and leukotrienes 2

Clinical Presentation

• Symptoms typically develop 5-10 minutes after exercise, peak 8-15 minutes post-exercise, and resolve within 30-90 minutes without treatment 2, 3
• Common symptoms include chest tightness, cough, wheezing, and shortness of breath 2, 4
• A refractory period of up to 3 hours after recovery may occur, during which repeat exercise causes less bronchospasm 3
• Symptoms can range from mild to severe, with most cases being mild to moderate but potentially impairing athletic performance 2

Prevalence

• EIB occurs in approximately 90% of patients with asthma and up to 40% of patients with allergic rhinitis 4
• The prevalence in the general population is estimated between 6-13% 4
• Elite athletes have a higher prevalence (30-70%) than the general population 2
• Specific sports carry higher risk due to environmental exposures:
  • Ice rink athletes: ~30% prevalence due to cold dry air and pollutants 2
  • Nordic skiers: high prevalence due to inhalation of cold, dry air 2
  • Competitive swimmers: 11-29% prevalence associated with trichloramine exposure 2

Diagnosis

• Diagnosis of EIB should be confirmed by demonstration of airways reversibility or challenge testing, as self-reported symptoms are not reliable for diagnosis 1, 2
• A positive diagnosis requires a decrease in FEV1 of ≥10% after exercise and symptoms consistent with bronchospasm 2
• Exercise challenge testing should ensure ventilation reaches at least 60% of maximum voluntary ventilation using dry air 1
• Alternative testing methods include:
  • Eucapnic voluntary hyperpnea (EVH) - more sensitive for detection of EIB than direct challenges like methacholine 1
  • Inhaled mannitol challenge - useful for assessing EIB in recreational or elite athletes 1

Management

Pharmacologic Treatment

• First-line treatment: Short-acting β2-agonists (SABAs) 15 minutes before exercise, providing protection in 80-95% of affected individuals 2, 4
• For persistent symptoms despite pre-exercise SABA:
  • Daily inhaled corticosteroids (ICS) 2
  • Leukotriene receptor antagonists (LTRAs) like montelukast 2, 5
• Mast cell stabilizing agents (cromolyn sodium or nedocromil) may be used before exercise 2, 4
• Avoid daily use of long-acting β2-agonists (LABAs) as monotherapy due to risk of side effects and tolerance development 2

Non-Pharmacologic Approaches

• Warm-up exercise before planned activity can help prevent EIB 2, 3
• Use of a face mask or scarf to warm and humidify air during cold weather exercise 2, 3
• Dietary modifications that may help include:
  • Low-salt diet
  • Fish oil supplementation
  • Vitamin C supplementation 2
• Avoid known triggers and high-pollution environments 2
• Choose sports with lower minute ventilation when possible 2, 5

Important Clinical Considerations

• EIB in asthmatic patients can indicate poor control of underlying asthma and suggests the need to initiate or step up therapy 1
• Approximately 9% of individuals with EIB have no history of asthma or allergy 4
• If symptoms persist despite appropriate treatment, consider alternative diagnoses such as cardiac conditions, other pulmonary disorders, vocal cord dysfunction, or anxiety 5
• The severity of EIB is related to the level of ventilation, heat and water loss from the respiratory tree, and the rate of airway rewarming and rehydration after exercise 4