Lung Cancer Risk Decreases at Higher Altitudes
Could breathing at sea level pose an unexpected health risk? A new epidemiological study suggests that at higher altitudes—where the air is thinner and oxygen levels are relatively lower—the incidence of lung cancer is reduced.
Researchers Kamen Simeonov and Daniel Himmelstein compared cancer rates among populations living at different elevations across the United States. The findings indicate that as altitude increases, the risk of lung cancer decreases.
The study was published on January 13 in the journal PeerJ.
Statistical Findings
The researchers estimate that if the U.S. population lived at elevations above 3,400 meters—such as near the summit of Mount Hood in Oregon—approximately 65,496 fewer lung cancer cases would occur each year.
For comparison, around 224,210 new cases of lung cancer were projected to be diagnosed in the United States in 2014.
These results suggest a possible association between lung cancer and altitude—and, indirectly, atmospheric oxygen concentration. Notably, other cancers not directly related to the respiratory system, such as breast, prostate, and colorectal cancers, did not show a statistical association with altitude.
Study Methodology
Simeonov and Himmelstein collected and analyzed epidemiological data from government databases covering 260 counties in the western United States.
The regions included in the study ranged from:
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Imperial County, California, located 11 meters below sea level,
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to San Juan County, Colorado, situated at 3,473 meters above sea level.
Across this elevation range, atmospheric oxygen concentration decreased by approximately 34.9%.
According to the findings:
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For every additional 1 kilometer increase in altitude, lung cancer risk decreased by 12.7%.
Were Alternative Factors Considered?
The researchers accounted for several potential confounding variables, including:
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Radon levels
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Climate variations
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Ultraviolet (UV) radiation exposure
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Fine particulate air pollution
The analysis indicated that none of these factors could fully explain the decrease in lung cancer rates observed with increasing altitude.
Oxygen: A Possible Mechanism
The researchers propose oxygen as the most likely contributing factor. Oxygen can lead to the formation of free radicals within cells—molecules that damage DNA and may initiate cancer development.
Paul Hwang, a physician-scientist at the National Heart, Lung, and Blood Institute, notes that experimental studies have shown that reduced oxygen levels can extend the lifespan of cancer-prone mice.
However, a paradox exists: previous studies have suggested that low oxygen concentrations may accelerate the growth of existing tumors.
Hwang explains this apparent contradiction as follows:
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Lower oxygen levels may help prevent the initial DNA damage that leads to tumor formation.
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However, once a tumor has formed, oxygen deprivation may promote more aggressive tumor growth.
The Smoking Factor Must Not Be Ignored
Elizabeth Platz, a cancer epidemiologist at the Johns Hopkins Bloomberg School of Public Health, described the study as “provocative and interesting,” but emphasized that it is observational in nature.
According to her, individuals seeking to reduce their risk of lung cancer would be far better advised to quit smoking rather than relocate to mountainous regions.
The researchers themselves also stress:
“We are not recommending that everyone move to higher elevations.”
Limitations
Like all epidemiological studies, this research has limitations:
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Lack of individual-level dietary data
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Lifestyle factors
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Smoking habits
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Overall health status
These variables were not fully controlled and may act as potential confounding factors.
Conclusion
The study suggests that lung cancer risk decreases with increasing altitude, and one possible mechanism behind this association may involve oxygen concentration. However, a causal relationship has not yet been established.
These findings may guide future mechanistic and molecular research and contribute to a deeper understanding of cancer development processes.