Disoriented and ataxic pilgrims: an epidemiological study of acute mountain sickness and high-altitude cerebral edema at a sacred lake at 4300 m in the Nepal Himalayas.

OBJECTIVE: To determine the incidence of high-altitude cerebral edema (HACE), acute mountain sickness (AMS), and high-altitude pulmonary edema (HAPE) in pilgrims. Although it is well known that western trekkers suffer from acute mountain sickness (AMS) in the Himalayas, not much is documented about the incidence of AMS in the local population of Nepal that go to high altitude. METHODS: The design was a randomized study set at a sacred high-altitude lake at 4300 m at Gosainkund in the Nepal Himalayas. There was a control study at 1300 m at Pashupatinath in Kathmandu, Nepal. The subjects were pilgrims of different ethnic Nepali backgrounds. The Lake Louise consensus for AMS, HACE, and HAPE was used, and oxygen saturation with a pulse oximeter was performed on HACE subjects. RESULTS: Out of 5000 pilgrims, 228 were randomly chosen. Sixty-eight percent had AMS, 31% had HACE, and 5% had HAPE. The mean oxygen saturation of HACE subjects at that altitude was 77%, 87% being normal for 4300 m altitude. Seventy-three percent of the study population were men, yet women had a significantly higher rate of AMS (odds ratio, 4.34; 95% confidence interval, 1.83-10.68), HACE (odds ratio 3.15, confidence interval 1.62-6.12), and HAPE (odds ratio, 5.2; 95% confidence interval, 1.24-24.73). CONCLUSIONS: Such a high incidence of HACE in an epidemiological study using the Lake Louise criteria has, to our knowledge, not been reported before. High-altitude pilgrims, especially women pilgrims in this study, seem to be a very susceptible group. Preventive measures in these pilgrims need to be adopted to avoid AMS, specifically life-threatening HACE and HAPE.