Hypoxia

Air gets "thinner" (less dense) with increasing altitude. Shortage of oxygen (hypoxia) and very low air (barometric) pressure can give rise to physiopathological problems. Persons transferring to and from high altitudes (above 3,000 to 3,500 metres) are susceptible to attacks of mountain sickness. Milder symptoms are: nausea, lethargy, headaches, lack of appetite, difficulty breathing, and sleeplessness. Individual response as regards severity and duration may vary, but working capacity is always affected. Persons transferred to high altitudes, even when acclimatized, remain susceptible to headache, insomnia, hypoxia and related conditions. The condition is aggravated by the increased intensity of ultraviolet radiation from the sun. Acute exposure to high altitude can severely reduce working capacity.

Approximately 25 million people live and work at altitudes over 3,000 metres.

Children and teenagers are more susceptible to altitude sickness than adults.