October 29, 2013
People who live at high altitude are well adapted physically to their environment but may suffer deficits in cognitive function, according to research findings by an Alma College professor and his students.
John Davis conducts ongoing research on the effects of high altitude exposure on humans. He and a team of students recently tested climbers at Mt. Chimborazo, located near the equator in Ecuador. The summit is 20,700-feet above sea level.
The research took place on the mountain base at the Carrel Refugio, a stopping-off facility for individuals seeking to climb to the mountain’s summit and tourists from Ecuador and throughout the world. The primitive building, located at 16,000-feet above sea level, offers bunks and water and is reachable by car.
“For the past four years we have studied how people who live permanently at high altitude adapt to high altitude differently from people who live at sea level,” says Davis, Alma’s Dana Professor of Integrative Physiology and Health Science. “We do a variety of tests that examine respiratory function, exercise response and cognitive ability.”
Davis’ most recent study looks at human cardiovascular adaptation to living at high altitude. The researchers conducted a well-validated clinical test called the stand test, in which subjects stand rapidly from a lying-down position.
“At sea level, most people adjust easily,” says Davis. “But at high altitude, this can be a challenge to the heart and blood vessels.
“We found that heart rate increases and blood pressure reductions were minimal for people who live at high altitude, while people of any ethnic background who permanently live at low altitude had a much harder time,” he says. “Our data suggests that high-altitude residence, more than ethnicity, influences cardiovascular responses to orthostatic stress.
“In a nutshell, high-altitude natives are well adapted to their environment,” he says.
Davis and his student co-authors, recent Alma College graduates Jessica Thorington and Cory Schall, along with Utah State University collaborator Dale Wagner, published their research in a recent issue of High Altitude Medicine and Biology, a peer-reviewed academic journal. It is the first published study to use a single ethnic group to evaluate high-altitude adaptation.
“This is a research finding that anyone might assume, but we have demonstrated it with solid research,” says Davis. “Plus, the Carrel Refugio is at 16,000 feet, which is approaching the highest altitude at which people can live permanently. We were at the precipice for this research — at the limits for people to live.
“The students were very helpful,” adds Davis. “We lived for nearly two weeks in a difficult environment — cold, windy, inside four walls and a roof. They adapted to the environment, spoke Spanish fluently and helped with the data collection.”
While high-altitude natives are well adapted physically, Davis sees evidence of cognitive deficits in related studies recently completed in high-altitude environments.
“We do simple tests that measure verbal fluency, muscle movement and task recognition and response,” says Davis. “We’ve found that people who live at high altitude tend to have lower responses to these cognitive challenges. There is speculation in the research literature that exposure to hypoxia, or low oxygen, might have some effect on the size of the brain, especially if exposed as children.”