Taggert Brooks points to this excellent news article by George Johnson, who reports:
Epidemiologists have long been puzzled by a strange pattern in their data: People living at higher altitudes appear less likely to get lung cancer. . . . The higher you live, the thinner the air, so maybe oxygen is a cause of lung cancer. . . .
But the hypothesis is not as crazy as it may sound. Oxygen is what energizes the cells of our bodies. Like any fuel, it inevitably spews out waste — a corrosive exhaust of substances called “free radicals,” or “reactive oxygen species,” that can mutate DNA and nudge a cell closer to malignancy.
Back to the epidemiology. Researchers Kamen Simeonov and Daniel Himmelstein adjusted for a bunch of demographic and medical variables, and then:
After an examination of all these numbers for the residents of 260 counties in the Western United States, situated from sea level to nearly 11,400 feet, one pattern stood out: a correlation between the concentration of oxygen in the air and the incidence of lung cancer. For each 1,000-meter rise in elevation, there were 7.23 fewer lung cancer cases per 100,000 people.
“7.23” . . . that’s a bit overprecise, there’s no way you could know it to this level of accuracy. But I get the general idea.
As Brooks notes, this idea is not new. He links to a 1987 paper by Clarice Weinberg, Kenneth Brown, and David Hoel, who discussed “recent evidence implicating reactive forms of oxygen in carcinogenesis and atherosclerosis” and wrote that “reduced oxygen pressure of inspired air may be protective against certain causes of death.”
The idea has also hit the mass media. For example, from a 2012 article by Michael Corvinus in Cracked (yes, Cracked):
One of the disadvantages of living at higher altitudes is that there’s less oxygen in the air, which can suck for those with respiratory problems. One of the advantages of those places, however, is that … there’s less oxygen in the air. A lack of oxygen makes people’s bodies more efficient, which makes them live longer. . . . Dr. Benjamin Honigman at the University of Colorado School of Medicine theorized that the lower levels of oxygen force the body to become more efficient at distributing that oxygen, activating certain genes that enhance heart function and create new blood vessels for bringing blood to and from the heart, greatly lowering the chances of heart disease.