High Altitude Sickness (Acute Mountain Sickness)
High Altitude Sickness (aka Acute Mountain Sickness) is the effect on the body of being in a high altitude environment. It is common at high altitudes, that is above 8,000 feet (2,440 meters). Three-quarters of people have mild symptoms over 10,000 feet (3,048 meters). The occurrence depends on the altitude, the rate of ascent, and individual susceptibility. Many people experience mild AMS during the acclimatization process (the first 1 to 3 days at a given altitude). Symptoms usually start 12-24 hours after arrival at altitude and include headache, dizziness, fatigue, shortness of breath, loss of appetite, nausea, disturbed sleep, and a general feeling of malaise. These symptoms tend to be worse at night when respiratory drive is decreased. Of course, all this would apply to ascending to high altitude in an airplane or balloon without a proper oxygen supply.