BACKGROUND: Allergens and pollution are reduced at high altitude. We investigated the effect of asthma rehabilitation at high altitude (HA, 3,100 m) compared to low altitude (LA, 760 m) on exhaled nitric oxide (FeNO) and on specific IgE levels for house dust mites (HDM-d1) and common pollen (sx1). METHODS: For this randomized controlled trial adult asthmatics living < 1,000 m were randomly assigned to a 3-week in-hospital-rehabilitation (education, physical- and breathing-exercises) at either LA or HA. Changes in FeNO, d1 and sx1 from baseline to end-rehabilitation were measured. RESULTS: 50 asthmatics (34 females) were randomized (mean +/- standard deviation LA n = 25, 44 +/- 11 years, total IgE 267 +/- 365 kU/l; HA n = 25, 43 +/- 13 years, total IgE 350 +/- 445 kU/l). FeNO significantly improved at HA from 69 +/- 56 ppb at baseline to the first day at altitude 23 +/- 19 ppb and remained decreased until end-rehabilitation with 37 +/- 23 ppb, mean difference (95%CI) -31 (-50 to -13, p = 0.001) whereas at LA FeNO did not change. A significant decrease in d1 and sx1 at end-rehabilitation was observed in the LA-group (mean difference (95%CI) -10.2 kUA/l (-18.9 to -1.4) for d1 and -4.95 kUA/l (-9.69 to -0.21) for sx1) but not in the HA-group. No significant difference between groups (d1 5.9 kUA/l (-4.2 to 16.2) and sx1 4.4 kUA/l (-3.5 to 12.4)) was found. CONCLUSION: Rehabilitation at HA led to significant FeNO reduction starting from the first day until end-rehabilitation despite unchanged levels of specific IgE. The significant decrease in d1 and sx1 at end-rehabilitation in the LA group might be explained by less HDM in the hospital and/or reduced seasonal pollen, as this decrease was not observed at HA.

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