Evaluation of the Lake Louise Score for Acute Mountain Sickness and Its 2018 Version in a Cohort of 484 Trekkers at High Altitude.

Richalet, Jean-Paul, Chantal Julia, and François J. Lhuissier. Evaluation of the Lake Louise Score for acute mountain sickness and its 2018 version in a cohort of 484 trekkers at high altitude. High Alt Med Biol. 00: 000-000, 2021.-The Lake Louise Score (LLS) is widely used in field studies and chamber studies for the diagnosis of acute mountain sickness (AMS). This score aggregates symptoms that are nonspecific: headache, gastrointestinal symptoms, fatigue, dizziness, and sleep disturbance can be due to a variety of causes unrelated to altitude hypoxia. The objectives of this study were to (1) reevaluate the need for a headache score >0 for the diagnosis of AMS, (2) evaluate the role of sleep disturbance, in relation to other symptoms, and (3) evaluate the significance of dizziness. We analyzed the LLS from 484 trekkers at high altitude. Among them, 212 suffered from mild-moderate AMS (mAMS: 3 ≤ LLS <6) and 115 from severe AMS (sAMS: LLS ≥6). Cluster analysis of AMS revealed three main groups demonstrating the following symptoms: Group 1 includes 254 subjects who had less than 2 symptoms, corresponding to no AMS; Group 2 includes 137 subjects who had fatigue, sleep disturbance, and headache, corresponding to mAMS; Group 3 includes 93 subjects who had headache, fatigue, dizziness, and sleep disturbance, corresponding to sAMS. A headache score of zero was found in 25% of subjects with mAMS and 5% of subjects with sAMS. Only the absence of a headache plus no fatigue was specific for the absence of sAMS. In subjects with a dizziness score >1, end-tidal partial pressure of carbon dioxide during a hypoxic exercise test was lower than that in subjects with a dizziness score <2. Subjects with a high ventilatory response to hypoxia may develop dizziness with high altitude exposure. In conclusion, (1) an isolated headache score >0 should not be mandatory to define AMS, (2) sleep disruption contributes to the diagnosis of AMS, (3) gastrointestinal symptoms and dizziness are weaker contributors to the LLS, and (4) dizziness might be linked to a hyperresponsiveness to hypoxia and not to AMS itself.