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Climb Every Mountain, Without Altitude Sickness

As more travelers seek out adventure at high elevations, altitude sickness is an often overlooked risk.

At popular destinations far above sea level, from the peaks of Nepal and the Pacific Crest Trail to the tourist attractions of Peru, the air gets thinner the higher you ascend. People often experience headaches, dizziness, and fatigue from a condition called acute mountain sickness before their bodies eventually adapt to lower oxygen levels in the blood. Untreated, it can progress to a potentially fatal swelling of the brain. And when people ascend in altitude too quickly, they can suffer a swelling of the lungs that can also lead to death.

Researchers are still uncovering some of the mysteries of altitude-related health problems. Genetic factors seem to make some people less susceptible to altitude sickness. People over 50 have a slightly lower risk, perhaps because the brain shrinks slightly as it ages. Men and women seem to be equally at risk, although symptoms might be more severe in men. And, interestingly, people’s fitness levels seem to have little to do with who is susceptible.

“Altitude illness is caused by the interaction of genes and the environment, and it can happen to the sedentary executive or the triathlete,” says Peter Hackett, director of the nonprofit Institute for Altitude Medicine in Telluride, Colo.

The most common preventive advice is to adjust gradually to higher elevations, which can take three to five days, Dr. Hackett says. Stop ascending if symptoms occur and head for a lower elevation if they get worse, he says. And avoid alcohol and strenuous exercise for the first 48 hours. Some doctors prescribe a drug such as acetazolamide to prevent mountain sickness, although side effects, such as dizziness and dry mouth, might be unpleasant.

People may feel symptoms of altitude sickness starting at about 5,000 feet—about the elevation of Denver. Real problems typically begin between 8,000 feet, the elevation of Aspen, Colo., and 10,000 feet, roughly that of Breckenridge Ski Resort. As many as 50% of people can develop acute mountain sickness at these heights, according to the Altitude Research Center at the University of Colorado Anschutz Medical Campus in Aurora.

An estimated 30 million people a year visit U.S. resorts and mountain towns in that range of altitudes, putting them at risk for mountain sickness, says Robert Roach, the center’s director. He says the average traveler may not learn about the risks because altitude illness isn’t widely discussed in the travel and tourism industries.