Even those fortunate enough to avoid such obvious symptoms of altitude sickness will suffer from delayed reactions and general malaise once they pass 6000 m due to the lack of oxygen; this also leads to impaired decision-making and memory, making the altitude as much a challenge as the terrain.
即便沒有這些明顯的高山症候，人處在六、七千公尺以上，因為缺氧，官能反應遲鈍、精神不集中，判斷力和記憶力都會減退，「高度」的考驗更甚於「地形」。