Background: Bronchial hyperresponsiveness (BHR) is related to asthma and is common in elite swimmers, likely due to high ventilation and repeated exposure to trichloramine in indoor pools. Winter sport athletes also show high BHR prevalence and therefore represent a relevant comparison group. However, little is known about post-retirement changes in these athletes. Aim: To examine longitudinal changes in methacholine responsiveness and lung function from career to post-retirement in elite swimmers compared to winter sport athletes. Methods: We included 13 swimmers, 61 cross-country skiers, 16 biathlon skiers, and 12 speed skaters, all competing at international level. BHR was assessed by the provocation dose of methacholine causing 20% reduction in forced expiratory volume in one second (PD**meth), and lung function by maximal expiratory flow-volume loops. Athletes were tested during active careers (1993-2016) and after retirement (2022-2024). BHR was defined as PD**meth < 6 µmol. Changes in BHR prevalence were analyzed using McNemar`s test, and lung function using paired t-tests. Absolute and relative changes, matched odds ratio, confidence intervals, and effect sizes were calculated for paired pre-post comparisons. Results: BHR prevalence decreased significantly in swimmers from 85% (11/13) to 23% (3/13), an absolute reduction of 62 percentage points (p=0.008). No significant changes were observed in winter cross-country skiing (41% to 34%; -7 percentage points), biathlon (56% to 50%; -6 percentage points), or speed skating (42% to 17%; -25 percentage points). Lung function remained unchanged across all sports. Confidence intervals were wide in the smaller sport groups and should be interpreted cautiously. Conclusion: BHR decreased markedly after retirement in elite swimmers, while remaining largely unchanged in winter sport athletes, suggesting reversibility after cessation of sport-specific environmental exposure. No significant lung function changes were observed.
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