Gaillard, Samuel, Pascale Dellasanta, Louis Loutan, and Bengt Kayser. Awareness, prevalence,
medication use and risk factors of acute mountain sickness in tourists trekking around the Annapurnas
in Nepal: A 12-year follow-up. High Alt. Med. Biol. 5:410–419, 2004.—Acute altitude
exposure may lead to acute mountain sickness (AMS). Increased awareness of altitude-related
health hazards in trekkers may accompany a decrease in AMS prevalence. We compared awareness
and AMS prevalence in trekkers in two cohorts on an altitude trek up to 5400 m and assessed
risk factors for AMS by repeating an observational cohort study 12 yr after an initial
study. Questionnaires in English were distributed to two cohorts of 500 trekkers in 1986 and
1998. All trekkers over a several day period were asked to participate. Average participation rate
was 62% (71% in 1986 and 53% in 1998). We found an increase in AMS awareness in trekkers
from 80% to 95%, a decrease in AMS prevalence from 43% to 29%, and significant slower climbing
profiles. We found no relationship between AMS and smoking habits, body mass index, oral
contraception intake, or training status. By contrast, age was a strong independent risk factor
inversely related to AMS. Subjects over 55 yr were 2.6 times less likely to suffer from AMS than
subjects under 25 yr. Self-medication, including acetazolamide and analgesics, had increased importantly
from 17% to 56%, and contraception intake in women had increased from 19% to 32%.
In conclusion, in 1998 as compared to 1986, trekkers were older, climbed more slowly, had better
awareness of altitude illness, used more medication, and suffered less from AMS.
