Are Pre-Ascent Low-Altitude Saliva Cortisol Levels Related to the Subsequent Acute Mountain Sickness Score? Observations from a Field Study.

Background: The associations among cortisol levels, body water status, and acute mountain sickness (AMS) remain unclear. We investigated associations between AMS prevalence and severity with resting saliva cortisol levels at low altitude (LA) and high altitude (HA) and with fluid balance during a HA stay. Methods: Twenty-two physically fit and healthy participants (12 women, 10 men) were transported to HA (Testa Grigia, 3480 m). In the late afternoon at LA, on the next day 3-4 hours after arrival at HA and in the morning after an overnight stay, heart rate, oxygen saturation, and systolic and diastolic blood pressures were measured in a sitting position after 10 minutes of rest; cortisol levels were quantified in saliva samples taken pre-ascent and 3-4 hours after arrival at HA. AMS was scored with the 1993 Lake Louise Score (LLS, cut-off ≥3). Urine volume and fluid and food intake were recorded during the altitude stay. Results: Pre-ascent cortisol levels were associated with fluid retention during the altitude stay ( r ²  = 0.33, p  < 0.05) and both were positively related to the LLS ( r ²  = 0.49 and r ²  = 0.26, p  < 0.05, respectively). Conclusions: In conclusion, resting LA cortisol levels and fluid retention upon rapid exposure to altitude seem to be associated with AMS. This suggests a potential link among cortisol homeostasis, fluid balance, and AMS risk.