Immunity, Inflammation and Airway Dysfunction in Elite Cross-Country Skiers and Ice Hockey Players: A Systematic Review.

Strenuous exercise in elite sports impacts the immune system, leading to high rates of upper respiratory tract infections and airway dysfunction, such as asthma and exercise-induced bronchoconstriction (EIB). Cross-country (XC) skiers and ice hockey (IH) players are particularly affected due to their training environments and sports disciplines. This systematic review (SR) evaluates immune and inflammatory responses and the risk of developing airway dysfunction in these athletes. Original articles focusing on immune response, systemic inflammation, and airway dysfunction in competitive XC skiers and IH players were retrieved from MEDLINE/Ovid, EMBASE, and the Cochrane Library. Risk of bias was assessed using the Cochrane Risk of Bias Tool. Of 3582 studies screened, 50 met the inclusion criteria. Both elite XC skiers and IH players exhibit increased cortisol levels and altered systemic immune cell compositions in response to training and competition. Both groups show neutrophilic or mixed neutrophilic/eosinophilic airway inflammation, in contrast to the primarily eosinophilic inflammation associated with allergic asthma. Both XC skiers (27%) and IH players (14%) had a high prevalence of physician-diagnosed asthma. This SR highlights the notable burden of airway dysfunction in elite winter athletes, with elevated rates of asthma and EIB. The observed inflammatory patterns support the concept of a "sport asthma" endotype, which may be a result of chronic exposure to cold, dry air. Effective management may benefit from refined diagnostic criteria, the identification of specific biomarkers, and tailored prevention and treatment strategies for asthma and EIB.