Background: Asthma has become one of the most prevalent chronic respiratory diseases worldwide, affecting between 1% and 29% of the adult population and between 9% and 11% of children (1-3). It has a significant impact on morbidity and mortality, as well as economic costs derived from loss of productivity, treatment in its various forms, and management of complications (4). Currently, there are several and varied treatment strategies that seek to achieve better control of the disease. However, it is estimated that between 5% and 10% of patients do not achieve adequate control of their symptoms and remain in a spectrum of severe asthma. This patient population requires novel treatment options that are cost-effective and straightforward to implement. In light of this, high-altitude climate treatment is proposed as an emerging therapy that has demonstrated beneficial outcomes in the management of various pulmonary conditions, including asthma (6). Methods: A systematic review of the literature was conducted in order to identify the effects of high-altitude climate therapy in patients with a diagnosis of severe asthma. A comprehensive search was conducted in PubMed, Embase, Scielo, Lilacs, and Google Academic and CENTRAL databases. The search terms included Emtree, MeSH, DeCS, and free text terms. Boolean operators were used to combine search terms. A search was conducted in all the databases previously described using the following search terms: (Asthma[Mesh]) AND (Altitude[Mesh] OR Alpine[Mesh]) and ('Asthma') AND ('Altitude' OR 'Alpine'). The study included primary human studies in children and adults with a diagnosis of severe asthma exposed to altitudes higher than 1,500 meters above sea level (masl). Duplicate publications, case reports, and prevalence studies were excluded. Studies that found any of the following as the main outcome were included: quality of life as measured by SGRQ and/or AQLQ, disease control as measured by ACQ and/or ACT, lung function as measured by FEV1 value and FEV1/FVC ratio, and allergy markers as indicated by absolute IgE value and/or absolute eosinophil count. Results: The evidence is statistically significant and of low certainty, indicating that intervention with climate therapy at high altitude (greater than 1500 m.a.s.l.) improves quality of life as measured by the AQLQ questionnaire (MD -1.64, 95% CI [-1.77 to -1.5]). The results demonstrated a statistically significant improvement in quality of life as measured by the AQLQ questionnaire (MD -1.64, 95% CI [-1.77 to -1.5]), as well as a statistically significant improvement in disease control as measured by ACQ (MD 1.56, 95% CI [1.35 to 1.77]). The evidence is insufficient to conclude that this type of intervention has a clinically significant impact on lung function, as measured by FEV1, despite yielding a statistically significant result (MD -7.38 [-7.65 to -7.11]). Further studies are required to evaluate the effect of high-altitude climate therapy on absolute eosinophil counts and IgE levels. Interpretation: High altitude climate therapy has statistically significant evidence with low certainty of evidence on symptom control and its impact on quality of life. No clinically significant but statistically significant evidence was found for lung function and further studies are needed to evaluate outcomes such as IgE and eosinophil count.
