Does change in barometric pressure per given time at high altitude influence symptoms of acute mountain sickness on Mount Fuji? A pilot study.

Background: Acute mountain sickness (AMS) is a common, transient condition characterized primarily by headaches, and it can also be associated with fatigue, dizziness, and nausea with vomiting. The symptoms of AMS are most pronounced after the first night spent at a new altitude. At sea level, changes in barometric pressure per given time have been associated with migraine headaches. We sought to investigate whether changes in barometric pressure, subjective sleep quality index, and other candidates contributed to the risk of developing AMS on Mount Fuji in Japan.

Method: We surveyed 353 trekkers who stayed overnight at a mountain lodge before summitting Mount Fuji. We collected information regarding sex, age, sleeping altitude at the hut, and perceived sleep quality index including sleep time. AMS was assessed with the Lake Louise Scoring system. Barometric pressure and ambient temperature were collected at the 5th station (2305 m) and at the summit (3776 m).

Result: The overall prevalence of AMS in our cohort was 41.4% (Lake Louise Score ≥ 3 with headache, n=146). Using logistic regression, three factors were combined to generate a robust model for determining the risk of AMS (with or without AMS). These included (1) Δ barometric pressure during ascent per hour, (2) sleepiness on rising, and (3) sleep refreshment assessed by perceived sleep quality index.

Conclusion: These results suggest that climbers who stay overnight at the lodge should keep a better physical condition of sleep, and would pay attention to information of barometric pressure condition to decrease their risk of AMS at the summit of Mount Fuji. Our observatory data indicated that an overnight staying in half way up to the summit does not necessarily reduce the AMS risk in both sexes and irrespective of age, at least, until 3776 m elevation.