Plain English Summary
Background and study aims
Exercise-induced dyspnea (shortness of breath) in athletes is common and is often attributed to asthma. However, all wheeze is not due to asthma and diagnosis and treatment should be based on careful clinical evaluation. Exercise-induced laryngeal obstruction (EILO) is an important differential diagnosis to asthma in athletes. In EILO, the larynx (voice box) is transiently obstructed during exercise resulting in decreased airflow and airway symptoms, typically with a sudden onset followed by rapid cessation when exercise is stopped. EILO is diagnosed with a continuous laryngoscopy during exercise (CLE) test, in which larynx is continuously visualized during peak exercise. This study aims to estimate the prevalence of EILO among athletes and to describe the natural history of EILO. Secondary aims of the study are to describe the prevalence of asthma and to what extent the conditions coexist.
Who can participate?
Healthy athletes at competitive level, 15-35 years of age
What does the study involve?
Participation in the study involves one or two visits at the Clinical Research Centre, where testing is done. Each visit includes a clinical examination by a physician, spirometry (lung function tests), asthma provocation test with a eucapnic voluntary hyperventilation test (EVH), skin prick test (only first visit), questionnaire, and continuous laryngoscopy during exercise (CLE) test.
What are the possible benefits and risks of participating?
The participants receive financial compensation of about £90 (SEK 1000). The pre-test requires exercise to exhaustion which may be uncomfortable for participants who do not frequently undertake high-intensity exercise. Oxygen uptake is measured using a mouthpiece and nose clip that might cause a little discomfort during exercise. Exposure to sub-zero temperatures is expected to cause short-lived cold-related symptoms. Blood sampling causes short-lived pain at the site of vein puncture. The lung function tests involve several large exhalations which may feel exhaustive in the moment.
Where is the study run from?
Clinical Research Centre, Östersund Hospital (Sweden)
When is the study starting and how long is it expected to run for?
April 2014 to November 2017
Who is funding the study?
1. VISARE NORR Fund, Northern Country Councils Regional Federation (Sweden)
2. Unit of Research, Education and Development, Region Jämtland Härjedalen (Sweden)
Who is the main contact?
1. Dr Tommie Irewall (public)
2. Dr Nikolai Stenfors (scientific)
Dr Tommie Irewall
+46 (0)63 153000
Dr Nikolai Stenfors
+46 (0)63 153000
EILO hos konditionsidrottare.
Prevalence of exercise-induced laryngeal obstruction and asthma among athletes
Athletes have a high prevalence of exercise-induced laryngeal obstruction (EILO).
Approved 26/03/2015, Regional Ethical Review Board Umea (Samverkanshuset Universitetsområdet, 901 87 Umeå, Sweden; +46 (0)90 786 7252; email@example.com), ref: Dnr 2015-43-31M
Single-center longitudinal cohort study
Primary study design
Secondary study design
Patient information sheet
Not available in web format, please use the contact details to request a participant information sheet
Prevalence of exercise-induced laryngeal obstruction (EILO) in athletes
Participants undergo a clinical examination by the study physician, dynamic spirometry, eucapnic voluntary hyperventilation test, skin prick test, and continuous laryngoscopy during exercise test (CLE). CLE test includes running on a treadmill at incrementing speed to >90% maximum heart rate, while video recording larynx with a nasal fiberscope.
Primary outcome measure
Prevalence and natural history of exercise-induced laryngeal obstruction (EILO), defined as laryngeal obstruction at glottic or supraglottic level using a visual scoring system, assessed with continuous laryngoscopy during exercise test (CLE), at the first and second visit (summer or winter season)
Secondary outcome measures
1. Current asthma, defined as a) physician-diagnosed asthma, and b) use of asthma medication in the last 12 months, evaluated by questionnaire at first visit
2. Bronchial hyperreactivity, defined as 10% decrease in FEV1 after EVH test, measured at the first and second visit (summer or winter season)
3. Allergy, defined as a) reaction with >2 mm wheal to skin prick test, and b) self-reported allergic symptoms, measured at first visit
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Competitive athlete ( i.e. not at recreational level)
2. Age 15-35 years
Target number of participants
Total final enrolment
Participant exclusion criteria
2. FEV1 <50% of expected value at spirometry
3. Blood pressure (mmHg) > 200 systolic or >100 diastolic at rest
4. Aortic aneurysm
5. Previous heart attack or stroke
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Clinical Research Centre, Östersund Hospital
VISARE NORR Fund, Northern Country Councils Regional Federation
Funding Body Type
Funding Body Subtype
Unit of Research, Education and Development, Region Jämtland Härjedalen
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Planned publications in peer-reviewed journals. Additional documents may be made available upon request.
IPD sharing statement
The data generated during and/or analysed during the current study are not expected to be made available due to a requirement in the ethical approval, where there is a statement that the data will not be shared with unauthorized persons. The data will be held in a server at Umeå University.
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)