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Background: Airway disorders related to exercise are common in adolescents but remain underrecognized. This thesis investigates the prevalence, course, and characteristics of exercise-induced bronchoconstriction (EIB) and exercise-induced laryngeal obstruction (EILO) in adolescent athletes as well as postexercise airway responses in athlete and nonathlete adolescents focusing on aspects of airway physiology and inflammation. 

Aim: The aim was to improve understanding of exercise-related airway responses in adolescents using epidemiological, clinical, and biomarker approaches. Objectives included assessing the prevalence and course of EIB and EILO in athletes, examining links between symptoms, fractional exhaled nitric oxide (FeNO), and postexercise airway responses in athletes and nonathletes, and exploring associations between systemic inflammation proteins, lung function, and airway responses in nonathletes.

Methods: Two adolescent groups were studied: athletes from a national sports high school (N=98) and nonathletes from the general population (N=143). All completed questionnaires, exercise challenge tests, FeNO measurement, and lung function assessment by spirometry and oscillometry; nonathletes also underwent plasma proteomic analysis. Studies I–II examined EIB and EILO prevalence and progression in athletes; Study III explored links between symptoms, FeNO, and postexercise airway responses in both groups; Study IV investigated associations between inflammatory proteins, lung function, and airway responses in nonathletes.

Results: Estimated EIB prevalence among athletes was 23% (95% confidence interval (CI) 14.5–33.8) and EILO 8% (95% CI 2.5–18.5). Self-reported exercise-induced dyspnea poorly predicted either condition. Both EIB and EILO were dynamic over two years. Ten participants had incident EIB, eight had persistent EIB, and five remitted. Reporting more asthma-like symptoms at baseline increased the risk of incident EIB (odds ratio (OR) 2.78; 95% CI: 1.16–6.58), while FeNO, aeroallergy, and sex were not associated with incident EIB. Incident EILO occurred in three and persistent EILO in two of 27 tested. Postexercise airway responses measured by spirometry and oscillometry showed modest concordance, indicating complementary insights into airway physiology by the two methods. Elevated FeNO was associated with EIB by both spirometric (adjusted OR 2.54; 95% CI: 1.05–6.12) and oscillometric criteria (adjusted OR 3.05; 95% CI: 1.18–7.9) in nonathletes, but not in athletes. Proteomic analyses identified the chemokine CCL19 as related to reduced baseline lung function, though no systemic proteins were associated with postexercise responses. 

Conclusions: Exercise-induced airway disorders like EIB and EILO are common but often overlooked in adolescent athletes. Because symptoms alone are unreliable, objective testing is essential. Differences in FeNO associations suggest distinct EIB mechanisms in athletes versus nonathletes. These results enhance understanding of exercise-related airway responses and support targeted diagnostic and management approaches. The association of CCL19 with lower baseline lung function in nonathletes also points to a possible link between immune activity and airway function in adolescents.