Endurance athletes training in cold air and chlorinated pools have more airway hyper-responsiveness and EIB, and symptoms alone don't identify it, so diagnosis needs breathing tests
Interpretation
Consistent direction across several studies: about 8% of Olympic athletes had asthma or airway hyper-responsiveness, concentrated in endurance sports (Fitch 2012); 69% of 32 elite swimmers and 28% of 32 elite cold-air athletes had hyper-responsive airways, with inflammation rising with training hours (Bougault 2009); EIB increased over two years in 7 national-team triathletes (Knöpfli 2007); in 158 elite cold-weather athletes (83 M, 75 F) symptoms were as common with normal as with positive tests (Rundell 2001). A guideline supports testing-based diagnosis and pre-exercise treatment (Parsons 2013), a review prioritises reducing irritant exposure (Kippelen 2012), and a meta-analysis of 7 small RCTs supports warm-ups with high-intensity efforts (Stickland 2012). Graded moderate rather than strong because nearly all data are from elite athletes and age-group triathlete prevalence is unknown.
Practical implication
Triathletes with cough, wheeze or chest tightness after hard winter sessions should get a medical assessment with breathing tests rather than self-diagnosing or borrowing inhalers; if diagnosed, follow prescribed treatment, use a warm-up with some hard efforts, and reduce exposure to very cold, dry air and poorly ventilated pools where practical. Extrapolated from elite athletes.
Sources
7 sources, independently verified.
ATS GRADE-based guideline. EIB is acute airway narrowing caused by exercise, common in asthma but also occurring without known asthma. Evidence quality ranged from low to high. Strong recommendations: a short-acting beta2-agonist before exercise for all patients with EIB; for persistent symptoms despite this, add a daily inhaled corticosteroid, a leukotriene receptor antagonist or a pre-exercise mast cell stabiliser.
Asthma or airway hyper-responsiveness affected about 8% of Olympic athletes, the most common chronic condition; markedly more prevalent in endurance athletes in Summer and Winter sports; many diagnosed later in life, suggesting endurance training may contribute; cold or polluted air a significant factor in some sports. Elite athletes; based on medication-approval records.
Airway hyper-responsiveness (methacholine) in 69% of swimmers and 28% of cold-air athletes; sputum neutrophils correlated with weekly training hours in both athlete groups; signs of bronchial epithelial damage in most elite athletes, possibly contributing to hyper-responsiveness. Elite athletes; hyper-responsiveness is not identical to EIB.
Two-year follow-up with 8-minute outdoor threshold track runs at about -9 to 4°C. Bronchial reactivity and EIB increased significantly (p<0.001); three athletes developed bronchial hyper-reactivity; extrapolated incidence 21–57% per year. Tiny elite sample.
Sport-specific exercise challenge with pre/post spirometry: 26% had an FEV1 fall over 10%; 29% reported two or more symptoms, similar in test-positive (39%) and test-normal (41%) athletes; post-race cough more common in test-positive athletes. Symptoms neither identified nor excluded EIB; diagnosis should use challenge spirometry plus history.
Endurance athletes repeatedly exposed to pollutants, irritants or allergens have higher risk of airway dysfunction; epithelial injury from airway dehydration during hyperpnoea and/or inhaled agents may lead via repair-related inflammation to hyper-responsiveness and asthma. Reducing exposure to irritants is the most important prevention; non-drug strategies can help; drug approaches not shown to prevent it.
Post-exercise FEV1 fall reduced by high-intensity (mean difference -10.6%, 95% CI -14.7 to -6.5) and variable-intensity warm-ups (-10.9%, -14.4 to -7.5); continuous low-intensity (-12.6%, -26.7 to 1.5) and continuous high-intensity (-9.8%, -26.0 to 6.4) not significant. Warm-up with high-intensity efforts a possible short-term non-drug strategy. Small studies; participant total not in abstract; published online 2011.