[Effects of high altitude on bronchial asthma]

Sojourns in the high mountains have been recommended to patients with asthma for many decades. It is the aim of this contribution to summarise the published studies about the effects of a stay at > 1500 m above sea level on asthmatic patients. These data from 428 adolescent and adult patients indicate an improvement of asthma symptoms and lung function during sojourns at high altitude. In many patients a reduction of the steroid therapy was achievable. Profound changes in the immune system have been demonstrated at high altitude, with a reduction of B- and T-helper cell activation. Total and mite-specific immunoglobulin E antibodies decrease significantly during longer sojourns. These changes are associated with a reduction of airway inflammation (e. g., reduction of eosinophil activation, NO exhalation and bronchial hyper-responsiveness). The fact that also patients with non-allergic asthma demonstrate a reduction of their airway inflammation at high altitude suggests that the high altitude climate has beneficial effects on asthma beyond the effects of allergen avoidance. High UV exposure and low humidity could be important additional factors, to explain the reductions in asthma severity in the high mountain climate. Larger controlled studies should be performed to prove the positive effects of the high altitude climate on asthma.