Comparing Serum Orexin-A Levels Between Affected and Non-Affected People to Acute Mountain Sickness

Acute mountain sickness occurs generally after ascent to altitudes higher than 2500m and is not related to the physical fitness. The aim of this study was to investigate the serum levels of Orexin-A in people with and without the Acute Mountain Sickness. For this purpose, 14 men and women subjects participated in this study, voluntarily. All subjects transferred from Tehran to 3700m altitude of mount by the Tochal cable car at 9 am. Then, after 20min of modest hiking, they reach to the Tochal summit shelter at about 3960m altitude. Blood samples collected for the measurement of Orexin-A levels at three times: before the transferring in Tehran, 30min after arriving at altitude, and after 24h staying at altitude. The diagnostic criteria for the acute mountain sickness was a score of at least three from the Lake Louise questionnaire with headache present. Half of the subjects (n=7) affected to acute mountain sickness. The independent sample t-test showed that the subjects with the acute mountain sickness had lower levels of Orexin-A in Tehran, significantly (p=.044). However, the Orexin-A levels of affected and non-affected subjects were not significantly different after 30min and 24h at altitude (p=.08 and p=.10, respectively). There were negative significant correlations between the Lake Louise questionnaire scores and Orexin-A levels in Tehran and at altitude (p=.025 and p=.044, respectively). In conclusion, the serum levels of Orexin-A at low altitude could be consider as a predictive factor for the susceptible people to acute mountain sickness at high altitude.