Figure.

The prevalence of acute mountain sickness (AMS) in 827 mountain-climbers at 4559 m as a function of the rate of ascent, pre-acclimatization, and susceptibility to AMS. Definitions: slow ascent, an ascent from 2000 m to 4559 m over more than 3 days; pre-acclimatization, more than 4 days spent above 3000 m in the preceding 2 months; non-suceptibility to AMS, prior experience of altitudes above 3000 m with no more than rare headache and a history score below 4 points. Darker columns indicate susceptible, lighter columns non-susceptible, mountaineers (modified from [5])