Quick Answer
There is no exact threshold altitude at which everyone is affected, but generally, altitudes above 8,000-9,000 feet (2,400-2,700 meters) start to show significant effects on most people.
Understanding Altitude Sickness
Altitude sickness, also known as acute mountain sickness (AMS), occurs when the body cannot adapt to the lower air pressure and lower oxygen levels at high altitudes. The effects of altitude sickness are not just about physical discomfort but can also be life-threatening. Symptoms include headaches, nausea, fatigue, and shortness of breath.
Symptoms and Progression
At altitudes between 8,000-10,000 feet (2,400-3,000 meters), most people will experience mild symptoms such as headaches and fatigue. These symptoms typically resolve within 24-48 hours with rest and hydration. However, if left untreated, AMS can progress to more severe forms, including high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). HAPE symptoms include cough, chest tightness, and shortness of breath, while HACE symptoms include confusion, loss of coordination, and severe headaches.
Prevention and Treatment
Prevention is key in avoiding altitude sickness. Gradual ascent, staying hydrated, and avoiding strenuous activities are essential. If symptoms do occur, descend to a lower elevation immediately, and seek medical attention if they worsen. Medications such as acetazolamide (Diamox) and nifedipine (Procardia) can help prevent and treat AMS, but always consult a doctor before taking any medication.
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