Humans can survive at high altitudes. However, if you go to a high altitude, your body needs to adjust properly by getting used to it slowly or you could get sick.
Living at high altitude can potentially improve your endurance during intense exercise. It may increase your aerobic capacity, lactic acid tolerance, and oxygen flow to your muscles. To prevent altitude sickness, climb slowly and reduce your intensity at high altitudes.
Sleeping at higher attitudes promote fitness as it provides enough exposure to stimulate the production of new red blood cells, whilst allowing you to maintain training quality at sea level.
Any level above 8000 feet above sea level one can experience altitude concern
High hemoglobin levels can lead to dizziness, fatigue, easy bruising and other symptoms.