For those who haven't summited 29,029-foot Mount Everest, it's nearly impossible to imagine the immense physical and psychological challenge of climbing to the top of the world. I've been as far as Base Camp, at 17,600 feet, where there's about 50 percent of the oxygen in the air as there is at sea level.
As you climb, less oxygen in your blood means less oxygen in your brain.
At 15,000 feet, your cognitive performance, mood, and central nervous system functioning start to lessen. In severe cases, being at high altitude for long periods or without first acclimatizing, you are at a higher risk for swelling of the brain, (high-altitude cerebral edema - HACE.)
If you ascend without proper acclimatization, at around 9,000 feet, your lungs may begin to swell because the blood vessels constrict. Symptoms include a persistent cough and labored breathing.
If the swelling in your lungs worsens, high-altitude pulmonary edema (HAPE) can occur. Symptoms are a bluish discoloration of the skin, rapid breathing, and fever. The most effective treatment is to descend immediately.
Sleep deprivation takes a sharp toll on the human brain and body, impairing cognition, motor ability, and mood. Willpower, memory, judgement, and attention all suffer. You drop and bump into things, crave sugar, overeat, and gain weight. You're more irritable, more anxious, overly negative, and more emotionally reactive.