I'm a mountain climber. Many times, I've climbed to elevations above 8,000 feet, but I have no memory of reaching the peaks of these mountains afterwards. What causes this?
The higher you climb above sea level, the less oxygen you have to breathe. At altitudes above 8,000 feet (2,424 meters, or m), the oxygen level becomes very low. If you normally live at or near sea level, your body simply isn't used to working with so little oxygen. This is why mountain climbers, hikers and skiers who ascend too rapidly to altitudes above 8,000 feet (2,424 m) may be affected by altitude sickness — which can cause, among other symptoms, amnesia and memory loss.
There are three main types of altitude illnesses:
- Acute mountain sickness. About 20 percent of people who climb to altitudes between 6,300 feet (1,911 m) and 9,700 feet (2,942 m) will develop mild symptoms of acute mountain sickness, also called altitude sickness. Symptoms may include headache, dizziness, nausea and difficulty sleeping. If symptoms are mild, they usually disappear after a day or two at the same altitude. If symptoms persist, go down 2,000 feet (606 m) to 3,000 feet (909 m) until you feel better. The faster and higher you go, the more likely you are to develop acute mountain sickness.
- High-altitude pulmonary edema (HAPE). In this condition, fluid accumulates in the lungs. Signs and symptoms include difficulty breathing even at rest, tightness in the chest, extreme fatigue and coughing. This requires prompt medical attention. You're more likely to get HAPE if you've had it before. It rarely occurs at heights below 10,000 feet (3,030 m).
- High-altitude cerebral edema (HACE). In this condition, excess fluid accumulates in the brain (brain swelling). Signs and symptoms include confusion, difficulty with balance and coordination, and hallucinations. HACE is a medical emergency and requires immediate medical attention and evacuation to a lower altitude. It most often occurs at heights above 10,000 feet (3,030 m).
Amnesia or memory loss can occur in conjunction with all three types of altitude illness. This may be due to the effects of oxygen deficiency, low body temperature (hypothermia) or certain medications. Amnesia may also occur after return from altitudes above 16,500 feet (5,000 m).
To avoid altitude illnesses, take the following steps:
- Ascend slowly. Give your body time to adjust to the lower amount of oxygen. Once you reach 8,000 feet (2,424 m), don't continue at more than 1,000 feet (303 m) a day.
- Limit your physical activity at heights over 8,000 feet (2,424 m).
- Rest often.
- Don't ascend to a higher altitude if you have a headache.
- Never ascend to a higher altitude if you are unable to walk an imaginary straight line (tandem walk). This may indicate early brain swelling and requires prompt immediate evacuation to a lower altitude.
- At night, sleep at an altitude lower than the altitude to which you climbed during the day.
- Carry an oxygen supply if you will be traveling for extended periods above 9,840 feet (2,982 m).
- Ask your doctor about medications such as acetazolamide (Diamox, Dazamide) to prevent or lessen the side effects of climbing to a high altitude. These drugs may be appropriate if you've had prior significant mountain sickness or if you won't have time to gradually acclimate to a high-altitude environment.
Last Updated: 03/03/2005
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