High Altitude Affects Brain Function

Cognitive decline can last months

Do you fancy an adventure vacation climbing a lofty peak in the Himalayas?

Don't be surprised if you're not quite as mentally sharp when you come back. Exposure to high altitudes can blunt certain mental functions such as coordination and math skills. Even elite climbers can be affected for two to 10 months after returning to lower altitudes, researchers report.

An acute medical condition known as mountain sickness or high altitude pulmonary edema can strike people who ascend too quickly to heights greater than 8,202 feet (2,500 meters). It causes headaches, fatigue, unsteadiness, nausea, shortness of breath, and, in rare instances, seizures and coma.

More subtle effects of high altitude may affect many more people, however, Science News reports. In the western United States alone, 30 million people live or visit altitudes above 5,000 feet (1,524 meters). At 12,000 feet (3,657 meters) blood oxygen levels drop so low that "your HMO or Medicare insurance would pay for you to have supplemental oxygen," says Frank L. Powell, a physiologist at the University of California, San Diego.

The article says that the high-altitude effects can be reversed by enriching the air with extra oxygen, which normally makes up 21 percent of atmosphere, regardless of altitude. Every additional 1 percent of oxygen added to the air is equivalent to a 1,000-foot (305-meter) drop in altitude.

Drugs that dilate blood vessels also seem to reverse some of the effects of high altitude. No one suggests that people living at high altitudes take such drugs on a regular basis. However, Ananova reports that people who ski or climb high mountains might take along the drugs, called vasodilators, to prevent or reverse the effects of altitude sickness.

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