Is poor sleep quality at high altitude separate from acute mountain sickness? Factor structure and internal consistency of the Lake Louise Score Questionnaire.

BACKGROUND: The factor structure and internal consistency of the Lake Louise Score Questionnaire (LLSQ) have not been determined in a large population at high altitude; however, a single-factor structure and a high internal consistency are preferable for accurate clinical and research applications of the LLSQ.
METHODS: A large group of Nepalese pilgrims (n=491) were assessed for acute mountain sickness with a verbal Nepali translation of the LLSQ after rapidly ascending from 1950 m to 4380 m. The factor structure and internal consistency of the LLSQ were determined with a confirmatory factor analysis (CFA) and the ordinal alpha coefficient, respectively.
RESULTS: A one-factor structure with all five items of the LLSQ was accepted. Four items (headache, gastrointestinal upset, fatigue/weakness, and dizziness/lightheadedness) loaded strongly on this factor (>0.70), but sleep quality had a low factor loading (0.33). The internal consistency (ordinal alpha coefficient) was 0.79, but removing the sleep quality item improved this value to 0.84.
CONCLUSIONS: The sleep quality item of the LLSQ was weakly related to the other items of the LLSQ. Future research should further investigate whether impaired sleep at altitude should be considered separately from other symptoms of AMS.