Working outdoors cuts risk of kidney cancer in men--study

Ultraviolet rays (UV) of the sun enable the skin to create vitamin D, which in turn, lowers the rate of renal cell carcinoma (RCC), the main form of kidney cancer.

Sara Karami of the National Cancer Institute in Rockville, who led the study, stated, "To our knowledge, this is the first case-control study to provide evidence of an inverse association between occupational UV exposure and renal cell carcinoma risk.

"One explanation for the inverse association between UV and cancer is the hypothesis that, in the skin, sunlight exposure increases the production of vitamin D, which travels through the blood to other sites in the body.

"This is particularly important with regard to kidney cancer, because the kidney is the major organ responsible for vitamin D metabolism and activity and for calcium homeostasis."

Sunlight exposure and risk of kidney cancer assessed
In an effort to determine the link between sunlight exposure and the risk of kidney cancer, the researchers enrolled 1,097 men and women suffering from the ailment and compared them to 1,476 healthy persons in Europe.

The participants were then split into three groups based on the potential exposure to daylight in their respective job profiles.

Factors like work history, demographic information, sex, age, body mass index, family history of cancers, hypertensive status, and smoking status were also taken into account.

Observations by researchers
The researchers noted that men working outdoors were at a 24 to 38 percent lower risk of developing kidney cancer.

In addition, men who lived in higher altitudes exhibited a 71 to 73 percent drop in cancer risk if they worked outside.

"Occupational sunlight exposure may be relatively more important in higher latitudes with lower intensity UVB, because residents there are less likely to reach the threshold of adequate sunlight exposure outside of work," the authors wrote.

However, the link between job-related sunlight exposure and kidney cancer risk was absent in women.

Plausible explanations for difference between the sexes
The researchers were confounded by the disparity of cancer risk in the two sexes. They attribute it to the biological or behavioral differences and higher tendency among the females to use sunscreen regularly.

Karami said, "Biological or behavioral differences between men and women may play a role. For example, hormonal differences may influence the body's response to sunlight exposure, and men may be prone to working outdoors while shirtless."

The study was funded by the National Institutes of Health and its details were published in the online version of the journal Cancer.