Acute Mountain Sickness in the Pyrenees: an observational cross-sectional study
Abstract Background The prevalence of acute mountain sickness (AMS) ranges between 15% and 80% depending on the absolute altitude reached, speed of ascent, and individual susceptibility. However, there is a lack of information regarding AMS at moderate to high altitudes (2,500-3,500 m) and, even less, in the Pyrenees. Our aim is to determine the prevalence and risk factor of AMS in the Pyrenees. Methods A cross-sectional study including mountaineers who climbed a mountain with a height greater than 2,500 m in the Pyrenees region during July and August 2019. Sociodemographic data, medical history and activity information were collected using a questionnaire. The diagnosis of AMS was based on the 2018 modified Lake Louise Score. A logistic regression analysis was performed to examine the association of different variables (risk factors) and AMS. Results From 437 participants, 117 met diagnostic criteria of AMS, establishing a prevalence of 26.7% (95% confidence interval: 22.6%-30.9%). Individuals affected by AMS had mild (88%) or moderate (12%) affection. The most common symptoms (in addition to headache which is mandatory for AMS diagnosis) were fatigue or weakness, gastrointestinal symptoms and dizziness. In an adjusted multivariate analysis, heavy perceived exertion, bad physical condition, nonsteroidal anti-inflammatory drugs use and previous history of altitude illness were independent risk factors for developing AMS. Conclusions One fourth of climbers in the Pyrenees experienced mild or moderate AMS. Previous history of AMS, nonsteroidal anti-inflammatory drugs use and other modifiable risk factors such as physical exertion and physical condition were strong and independent predictors of AMS. These findings suggest that educational/informational programs for individuals planning to climb to moderate-high altitudes in the Pyrenees may contribute to prevent AMS.