Lung Cancer Rates Lower at Higher Elevation Levels

Higher elevation levels could be the reason for lower lung cancer rates in the western United States, researchers from the University of Pennsylvania Perelman School of Medicine believe.

A lower incidence of lung cancer may be linked to living at high elevation, according to findings published online on PeerJ.

Researchers from the University of Pennsylvania Perelman School of Medicine studied age adjusted cancer incidence across counties of the western United States, which varies in elevation levels, and observed respiratory (lung) cancer and non respiratory cancer (breast, colorectal, and prostate) trends between 2005 and 2009. The data used in the study was compiled by the National Cancer Institute.

The researchers determined that for every 1,000 meter increase in elevation lung cancer incidence decreased by 7.23 cases per 100,000 individuals, or 12.7 percent of the mean incidence. In the 260 counties which make up 11 western states observed, the mean incidence is 56.8 lung cancer cases for every 100,000 people. Elevation was only second to smoking in terms of significance and effect size on lung cancer incidence in the varying county populations. The findings were true among both smokers and non smokers alike, though lung cancer primarily affects smokers. More than 80 percent of smokers never develop lung cancer, while 10 to 15 percent of non smokers do develop lung cancer, the authors noted.

“Lower atmospheric pressure at higher elevations results in less inhaled oxygen, sometimes as much as one third less than low elevation areas,” study co-author Kamen P. Simeonov, who is studying for a medical degree and a doctorate, said in a press release. “Non acclimated professional and amateur athletes know this very well. Our study suggests that this factor may explain why lung cancer incidence rates decrease as geographic elevation increases, but not rates for such equally pernicious cancers as colorectal, breast, and prostate.”

Previous studies indicated an inverse relationship between elevation in lung cancer rates, and scholars have hypothesized that incomplete or faulty metabolism of oxygen during normal breathing can lead to cell injury or mutation, which could lead to the development of lung cancer.

“Vitamin D synthesis is stimulated by sunlight and we know that the hormonally active form of vitamin D, calcitriol, potentially possesses anti cancer properties,” Simeonov explained, because the researchers additionally examined sunlight as a factor in their research. “Hence, a reasonable proposition would be that increased vitamin D synthesis and not elevation per se is the primary explanation for the lower rates of lung cancer at higher elevations.”

The authors estimated that if the entire United States sat at the same elevation level as San Juan County, Colorado (3,473 meters), 65,496 fewer new lung cancer cases would arise per year (based on the 2000 Census). They believe this statistic should be eye catching for researchers, health care providers, and the general public because the link appears to play a notable role in lung carcinogenesis.