The incidence of and risk factors for acute repiratory illness in athletes, and exercise-induced laryngeal obstruction

SEMLI researchers are part of an International Olympic Committee (IOC) Consensus Group on Acute
Respiratory Illness in the Athlete. They have recently published 3 Reviews detailing different aspects of
acute respiratory illness. These included: risk factors associated with acute respiratory illness, the
incidence of acute respiratory illness in athletes, and a review of exercise-induced laryngeal obstruction
(EILO) in athletes.

Approximately half of all medical consultations at international sports events such as the Olympic,
Paralympic and Youth Olympic Games are due to acute illness in athletes, of which the respiratory
system is the area most commonly affected. Acute respiratory illness may occur at various stages of
training, during competition and in recovery periods. These illnesses can interrupt training, impact
competition performance and may even pose a serious threat to the athlete’s health. It is therefore
important for clinicians to know how many acute respiratory illnesses they can expect in their team,
over what period and which athletes may be more susceptible to acute respiratory illnesses. A Sub-
group of the IOC Consensus Group aimed to answer these questions by performing a systematic review
and meta-analysis to determine the overall incidence of acute respiratory illness, including subgroups
categorised by pathology (acute respiratory infection vs undiagnosed acute respiratory illness),
predominant anatomical region affected (upper vs lower respiratory tract or general), different levels of
athletic performance (elite vs non-elite athletes), age groups (15–35 years vs >35 years) and season
(summer vs winter). They found that the overall incidence of acute respiratory infections among
athletes was 4.9 per 1000 athlete days, which translates to approximately 1.8 infections per athlete per
year. Upper respiratory tract infections were the most common, and the incidence of acute respiratory
infections in studies in elite athletes was significantly lower compared to non-elite athletes. The
incidence was found to be similar in older and younger athletes, and across studies conducted in
summer and winter. The researchers recommended that the diagnosis of acute respiratory infections in
clinical practice should be based on physician clinical assessment and laboratory confirmation of the
pathogen where possible, since pathogen confirmation is the most definitive diagnostic method.

Since acute respiratory illness and infections are common medical complaints in athletes, it is important
for clinicians and training staff to understand the types and magnitude of risk factors predisposing
athletes to these illnesses/infections. Risk factors associated with acute respiratory illness and infections
can be categorised by individual athlete factors (age, gender, medical history and co-morbidities), sport
(type and level of participation), training and competition factors, nutritional factors, environmental
factors (season, air temperature, pollution, altitude), exposure factors (international travel, household
exposure, personal hygiene, physical distancing, crowded and indoor environments), and
immune/haematological risk factors and biomarkers. A Sub-group of the IOC Consensus Group
performed a systematic review of risk factors associated with general (undiagnosed) acute respiratory
illness and infections (suspected or confirmed by laboratory identification of the pathogen) in athletes.
The review identified several modifiable risk factors that could be considered by sports coaches when
preparing training programmes, particularly for athletes who experience recurrent episodes of acute
respiratory illness/infection and those at a less competitive level. Risk factors included increased training
monotony, endurance training, lack of tapering, training during winter and at altitude, and international
travel. It is also important for clinicians working with athletes to consider vitamin D deficits, particularly
those prone to repeated acute respiratory illness/infections. Biomarkers for monitoring athletes at a higher risk of acute respiratory illness/infection included low tear-SIgA concentrations and low salivary-
IgA concentrations.

A third review by a Sub-group of the IOC Consensus Group on Acute Respiratory Illness in the Athlete
presents an overview of exercise-induced laryngeal obstruction (EILO), and guidance on how to evaluate
and treat suspected cases of EILO in athletes. EILO is increasingly recognised as an important cause of
exertional breathing problems or upper airway obstruction/dysfunction, particularly affecting athletes
and physically active young individuals. EILO is common, it has an impact on exercise performance and
quality of life, and tends to be confused with and inappropriately diagnosed or treated as lower airway
dysfunction (ie, asthma, exercise-induced bronchoconstriction, airway hyper-responsiveness). The
incorrect diagnosis and management of EILO can result in individuals being incorrectly prescribed
asthma medications, with an associated potential to cause adverse effects. The review focuses on the
pathophysiology of EILO, outlines a diagnostic approach and presents some of the most applied
treatment strategies. The ‘gold standard’ to diagnose and categorise EILO in athletes is by means of
continuous laryngoscopy performed during high-intensity exercise. Subtypes of EILO in athletes
(supraglottic and glottic) are described and may require different therapeutic approaches. New
algorithms for evaluation and treatment of EILO in athletes are presented, based on expert opinion and
best available evidence.

References used in this summary:
Derman W, Badenhorst M, Eken M, et al. Br J Sports Med Epub ahead of print: doi:10.1136/bjsports-
2021-104795
Derman W, Badenhorst M, Eken MM, et al. Br J Sports Med Epub ahead of print: doi:10.1136/
bjsports-2021-104737
Clemm HH, Olin JT, McIntosh C, et al. Br J Sports Med Epub ahead of print: doi:10.1136/
bjsports-2021-104704