Like it sounds, exercise-induced asthma is asthma that is triggered by vigorous or prolonged exercise or physical exertion. Most people with chronic asthma experience symptoms of asthma during exercise. However, there are many people without chronic asthma who develop symptoms only during exercise.
What is Exercise-induced Asthma?
Exercise-induced bronchoconstriction affects 40%-90% of people with asthma, compared with 3-15% of the general population. Exercise-induced asthma (EIA) is diagnosed on the basis of subjective symptoms of airflow obstruction during and after exercise, objective measures of airflow obstruction and the exclusion of alternative diagnoses.
Although the pathogenesis of EIA has not been fully elucidated, two major theories have been proposed : the airway rewarming theory and the hyperosmolarity theory. Increasing evidence suggests that airway inflammation plays a major role in the pathogenesis of EIA.
Of the many non-pharmacologic and non-immunologic contributors to airway obstruction in patients with asthma, exercise is one of the most common stimuli, ranking second only to viral respiratory tract infections.
Exercise-induced airway narrowing, exercise-induced asthma (EIA) and exercise-induced bronchospasm/bronchoconstriction (EIB) are synonymous terms that are used to describe acute narrowing of the airway triggered by vigorous physical activity in people with bronchial hyper-responsiveness (BHR).
Although the pathogenesis of EIA is not fully understood, this condition probably results from exercise-induced hyperventilation and changes in airway physiology. The prevalence of asthma and other similar phenotypes have been investigated using written and video questionnaires, developed for the International Study of Asthma and Allergies in Childhood (ISAAC).
The prevalence of exercise-induced wheeze ranges from 5.4% to 31.4%, depending on the time of the investigation and the characteristics of the study population (i.e., age and location). Traditionally, EIA is evaluated on the basis of a 10-15% decrement in the forced expiratory volume in 1 s (FEV1) or the peak expiratory flow (PEF).
Epidemiological surveys have determined that the prevalence of EIA in children from the general population ranges from 3.1% to 16%. In addition, some studies have observed a slightly higher incidence in girls and children living in urban areas. These observations suggest that social and environmental factors (e.g., wealth, lifestyle and housing environment) are important determinants of EIA.
Approximately 40%-90% of people with asthma experience EIA. The wide range in percentiles probably reflects study-specific differences regarding the intensity of the exercise used to produce obstruction (as well as variations in the definition of EIA) and in the methods used to detect the response (as well as a failure to standardize environmental variables, such as temperature and humidity, which can influence the magnitude of the obstruction).
Symptoms of exercise-induced asthma include wheezing, tightness or pain in the chest, coughing, and in some cases, prolonged shortness of breath. Some symptoms are more noticeable than others, which mean exercise-induced asthma can sometimes go undiagnosed.
Someone may have exercise-induced asthma if he or she :
- gets tired easily during or after exercise
- coughs after coming inside from being active outdoors
- can’t run for more than a few minutes without stopping
Kids with exercise-induced asthma often begin having symptoms 5 to 10 minutes after starting to exercise. Symptoms usually peak 5 to 10 minutes after stopping the activity and may take an hour or longer to end. Some people with EIA even have symptoms for hours after exercise. Although symptoms often appear while kids are active, sometimes they can appear only after the activity has stopped.
Of course, there’s a difference between someone with exercise-induced asthma and someone who’s out of shape and is simply winded. Out-of-shape people can catch their breath within minutes, whereas it takes much longer for someone with EIA to recover. And extremes of temperature, especially cold weather, can make it even worse.