Although exercising in cold air has minimal influence on airways of normal individuals,
Although exercising in cold air has minimal influence on airways of normal individuals
it can induce a bronchoconstriction in asthmatic subjects and worsen airway obstruction in those with obstructive pulmonary diseases . Winter athletes can be particularly affected by these environmental conditions, and an increased prevalence of airway hyperresponsiveness, asthma and chronic cough has been described in this population .
Bronchial biopsies of winter athletes have shown evidences of airway remodelling, possibly due to the repeated cold-air and hyperventilation damage to the airways, although more research is needed on this influence on airway function . The mechanism of bronchoconstriction as a response to exercise-induced hyperpnoea, particularly in cold air, has been studied and seems mostly related to an increase in airway fluid osmolarity following hyperpnoea, although heat loss may be a modulator of this response, as well as a possible post-exercise “rewarming” of the airways . Even in normal subjects, cold air can induce changes in the airways. Exposure to cold air can increase the number of granulocytes and macrophages in the lower airways . Furthermore, cold-related impairment of respiratory mucociliary function can inhibit the clearance of pollutants .
Finally, in extreme cold temperatures, people tend to gather indoors and crowding can promote the transmission of infectious agents with ensuing airway inflammatory events. Role of the upper airways in health and asthma Breathing cold air has been long recognized to trigger bronchoconstriction in asthmatics. In a classical experiment Shturman-Ellstein et al., demonstrated that if subjects with asthma breathed only through the nose during the exercise challenge, an almost complete inhibition of the post exercise bronchoconstrictive airway response was observed . However, as the nose is serving as outermost filter for the inspired air, it is exposed to environmental hazards with consequent high incidence of morbidity.
Adding to this genetic atopic predisposition, it is likely that asthmatic subjects have concomitant rhinitis, which does not allow proper conditioning of the inspired air with negative impact on the asthmatic condition. The cross-talk and interplay between upper and lower airways has been a center point in the philosophy of the Allergic Rhinitis and its Impact on Asthma (ARIA) initiative and has been reconfirmed over the years .
The upper airways mucosal structures are particularly sensitive to cold air influences. Challenges with cold dry air have been proposed to assess the state of nasal responsiveness in both allergic and non-allergic rhinitis . This line of research is substantiating the importance of cold weather as trigger in the pathogenesis of rhinitis, which in turn is a recognized risk factor for the development of asthma . Cold weather spells as a characteristic feature of changing climate will need to be considered in assessing the risk for asthma, especially since heterogeneous human populations may adapt differently to them .
Conclusions There is a need to better define the consequences of repeated exposure to cold air and the mechanisms by which such exposure could modify airway function and affect the outcomes of patients with pre-existing airway disease. This could help promote adequate policy and public health actions to face the incoming challenges. By all means distinction should be drawn between effects to individuals and effects to populations, as populations are heterogeneous in their susceptibility, reversible and irreversible effects should be identified .
Prof. Gennaro D’Amato, University Professor of Respiratory Medicine. Chairman committee on “Climate Change, Biodiversity and Allergy, World Allergy Organization. email@example.com