Abstract
Background: Acute mountain sickness (AMS) is the most common form of altitude illness. Several
risk factors have been suggested in the literature: some (absolute altitude, rapidity of ascent,
individual susceptibility, lack of acclimatization) are well established, others are more debated.
Limited sample size may have reduced the power of previous studies to identify these alternative risk
factors for AMS
Objectives: To study potential determinants of AMS in a large sample.
Methods: Data from three retrospective observational cross-sectional studies conducted in Nepal in
1986, 1998 and 2010 with a total of 956 trekkers stopping in Manang or in Muktinath (3500 m),
crossing a 5400 m high mountain pass, Thorong-La. Age, sex, height and weight, BMI, health
history, nationality, smoking status, profession, previous altitude experience, group sizes, rate of
ascent, medications used and carried and self-quantification of AMS symptoms (ESQ-III
questionnaire) were analyzed. An AMS-C score of ≥ 0.7 was considered to identify subjects
suffering from AMS.
Results: Prevalence of AMS was 32%. Using a bivariate analysis, sex (p = 0.002), age (p = < 0.001),
height (p =0.012), weight (p = 0.033), previous altitude experience (p = 0.004) and group size (p =
0.010) were significantly associated with AMS.
Age (odds ratio [OR], 0.970; 95% confidence interval, 0.954 to 0.986; p < 0.001), female sex [OR=
1.610 (1.163 to 2.229) p = 0.004] and body mass index [OR=1.099 (1.030 to 1.172) p = 0.004] were
significant predictors of AMS when using multivariate analyses.
Conclusion: Consistent with pre-existing literature, young age and female sex were significant risk
factors of AMS also in our cohort. Although debated in the literature, increasing BMI represented a
significant AMS predictor in our population.