Lung cancerExposure to sunlight

There are a number of ecological studies finding an inverse correlation between indices of solar UVB lung cancer irradiance and incidence and/or mortality rate.

The first studies to identify a reduction in lung cancer rates with respect to an index of solar UVB irradiance were three studies that examined the risk of cancer with respect to altitude. All three found that risk of lung cancer and several other cancers was reduced for those living at higher elevations123. None of these studies, however, identified UVB as the reason for the finding.

Study of cancer risk associated with occupation is another way to ascertain the role of solar UVB.

Farmers work out of doors and get much higher solar UVB irradiance than most other people. Farmers have much lower incidence and mortality rates for lung cancer than the general population in numerous studies: Missouri, United States, incidence risk ratio (RR) = 0.76 (95% confidence interval (CI), 0.66-0.86)4; North Carolina mortality rate, standardized mortality rate = 0.4 (0.3-0.5) 5; Nordic countries, standardized incidence ratios: Denmark: 0.47; Finland: 0.77; Iceland: 0.52; Norway: 0.46; Sweden: 0.40; Nordic country total: 0.56 (0.55-0.57) 6.

In an ecological study of cancer mortality rates in the United States, an inverse correlation between summertime solar UVB and lung cancer mortality rates was found for black males but not white males or females78. The region with the highest lung cancer rates in the U.S. is the southeast9. This region also has the highest cervical and liver cancer rates9, as well as heart disease rates [American Heart Association, 2010]. The reason for the high rates in the southeast may be dietary factors may increase the risk of cardiovascular disease and several types of cancer such as highest consumption of monounsaturated fatty acids, polyunsaturated fatty acids and cholesterol10.

Two studies investigated the correlation of lung cancer mortality rates in China with respect to latitude. One found an insignificant inverse correlation11 while the other found a significant inverse correlation with respect to a better UVB index12. However, the second study did not find any effect of UVB dose on lung cancer incidence rates.

A multi-country ecological study found “Lower levels of UVB irradiance were independently associated with higher incidence rates of lung cancer in 111 countries” in a model that included information on cigarette consumption 13. However, the fraction of lung cancer rates associated with solar UVB indices was 10-15%.

A good overview of the evidence regarding vitamin D and lung cancer is found in a recent review by Ramnath et al14.

Page last edited: 22 August 2011

References

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