People who live at high altitudes enjoy reduced rates of lung cancer, according to a new study.
A team led by Dr Kamen Simeonov of the University of Pennsylvania, USA, looked at the possible link with inhaled oxygen concentration.
They explain that when oxygen is quickly consumed by our cells, it produces reactive oxygen species (ROS) which can trigger cellular damage and mutation.
At higher elevations, lower pressure leads to less inhaled oxygen and possibly reduced oxygen reaction, they say.
The team compared cancer rates across the Western US, which varies in elevation. As elevation increased, lung cancer decreased, they report in the journal PeerJ.
"Lung incidence decreased by 7.23 cases per 100,000 individuals for every 1,000 meter (3,281 feet) rise in elevation," they state, taking into account other risk factors and demographic variables. This trend was not seen for non-respiratory cancers including breast, colorectal, and prostate cancer, they add.
They also found that environmental correlates of elevation, such as sun exposure and fine particulate matter (a measure of pollution), were much less closely linked to lung cancer rates than height above sea level.
"Overall, our findings suggest the presence of an inhaled carcinogen inherently and inversely tied to elevation, offering epidemiological support for oxygen-driven tumorigenesis," they write.
"Finally, highlighting the need to consider elevation in studies of lung cancer, we demonstrated that previously reported inverse lung cancer associations with radon and ultra violet B became insignificant after accounting for elevation."
Simeonov, K. P. and Himmelstein, D. S. Lung cancer incidence decreases with elevation: evidence for oxygen as an inhaled carcinogen. PeerJ 13 January 2015 doi.org/10.7717/peerj.705 [abstract]
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