Rate of ascent and acute mountain sickness at high altitude.

Background: A variety of risk factors have been identified that contribute to the development of acute mountain sickness (AMS), including past history, ascent rate, exertion prior to ascent, and cardio-pulmonary comorbidities. Ascent rate and other factors associated with AMS-induction are currently examined. Research question: It was hypothesized that rapid ascent is more likely to result in AMS than slow ascent. Type of study: Prospective study. Methods: Group allocation was by subject's preference. Young adults (18-26 years old) (N=91) chose to participate in 1 of 2 groups: Group 1 (fast ascent [3 days]; n=43) and Group 2 (slow ascent [4 days]; n=48). Groups hiked from 2370m to 3350m. Physiological measurements, including heart rate, oxygen saturation, and symptoms of AMS were monitored each morning and evening during the 5-day expedition to Jiaming Lake, Taiwan. Results: Baseline characteristics were similar between groups, except for significant differences in alcohol consumption (P=0.009) and climbing experience above 3000m (P<0.001). The incidence of AMS was not associated with the rate of ascent and was similar between groups. AMS-incidence was most prevalent in Group 1 at day 2 evening and Group 2 at day 3 evening that correlated with the initial reduction in SaO2 in each group. BMI>24 kg/m² was identified as a risk factor for AMS. Conclusions: The incidence of AMS was not associated with the rate of ascent. The development of AMS was closely associated with initial reduction of SaO2. BMI>24 kg/m² also contributed to the occurrence of AMS. [ABSTRACT FROM AUTHOR]