Environmental risk factors for altitude illness
Environmental factors that impact the risk of altitude illness include:
- rate of ascent
- maximum height achieved
- sleeping elevation
- strenuous exertion at altitudeBeidleman, 2013.
The Wilderness Medical Society categorises levels of risk for developing acute mountain sickness (AMS) for unacclimatised travellers, according to their pattern of ascentLuks, 2019.
Examples of low-risk ascent include:
- a person with no history of AMS ascending to 2800 metres or less as their final altitude in 1 day
- a person who takes 2 days or more to arrive at 3000 metres, and who has subsequent increases in sleeping elevation of no more than 500 metres per day, plus an extra day for acclimatisation for every 1000 metres of ascent.
Examples of moderate-risk ascent include:
- a person with a history of AMS ascending to 2800 metres in 1 day
- a person with no history of AMS ascending to over 2800 metres in 1 day
- a person above 3000 metres increasing their sleeping elevation by more than 500 metres per day (but who still allows an extra day for acclimatisation every 1000 metres).
Examples of high-risk ascent include:
- a person with a history of AMS ascending above 2800 metres in 1 day
- a person above 3000 metres increasing their sleeping elevation by more than 500 metres per day without allowing extra days for acclimatisation
- a person ascending to more than 3500 metres in 1 day
- a person ascending very rapidly (eg Mt Kilimanjaro in less than 7 days)
- a person with a history of high-altitude pulmonary oedema (HAPE) or high-altitude cerebral oedema (HACE).