Lung cancer is less common among people living at high altitudes, according to a new study from the University of California and University of Pennsylvania.
Lung cancer is responsible for 27 percent of all cancers in the United States, killing roughly 160,000 Americans each year. Smoking is deemed to be the cause of 90 percent of these cases. However, a new investigation suggests that atmospheric oxygen may be responsible for raising the risk of this form of cancer.
When oxygen is absorbed quickly into human lungs, it can create reactive oxygen species (ROS) of molecules. These are highly-reactive molecules containing oxygen, which have been suspected of causing cellular damage.
Oxygen makes up about 21 percent of the atmosphere. However, higher air pressures at lower altitudes results in the intake of greater quantities of oxygen being absorbed by residents in those locations, compared to those at higher altitudes. This effect can pose a major challenge for athletes performing in regions located significantly higher than where they train.
Researchers examined instances of lung cancer in various counties across the mountainous western United States. They found that the likelihood of developing lung cancer was significantly lower for people living at higher altitudes. For every 3,281 feet of altitude, the risk of lung cancer decreased by 7.23 cases per 100,000 people. A range of statistical analysis techniques were used to confirm this relation was not due to chance. The correlation was apparent both in the raw data, and when corrected for smoking rates and education.
Prostate, breast, and colorectal cancer rates were also examined in the study, but little to no association appeared between those forms of cancer and altitude. This finding lends support to the idea that oxygen could be the culprit behind greater incidence of lung cancer in people living at lower altitudes. Pollution in the form of airborne particulate matter and sun exposure were also examined as possible causes of the cancer cases, and no correlation was found.
"[If] the entire United States situated at the elevation of San Juan County, CO (3473 m), we estimate 65,496 fewer new lung cancer cases would arise per year," researchers wrote in a study profiling their findings.
Researchers on the study hope their findings will help others learn about the causes of lung cancer around the nation. However, they are not recommending that people move to higher altitudes in order to reduce risk of the disease.
Lung cancer incidence decreases with elevation: evidence for oxygen as an inhaled carcinogen, detailing the study of altitude and the disease was published in the journal PeerJ.
