Risk Factors

Dietary Factors. Dietary factors may play some small role in the higher risk in African men. This is suggested by the fact that prostate cancer is rare in many parts of Africa.

Biologic Factors. Some evidence suggests that African American and Asian men have certain genetic factors that may affect male hormones differently and so help account for the higher risk in the first group and the lower risk in the second. Other research reports that African American men have lower levels than Caucasian men of a protein called insulin-like growth factor binding protein 3 (IGFBP3), which may protect against cancer. (Insulin-like growth factor-I is a hormone that may increase the risk for prostate cancer in any man.) Still, evidence is weak on such genetic and biologic differences and more research is needed.

Higher PSA Levels. African American men also tend to have higher PSA levels than Caucasians. They are overdiagnosed with prostate cancer by 37% compared to 15% in Caucasians using PSA screening tests.

High Exposure to Chemicals and Electromagnetic Fields

Chemicals. The relationship between prostate cancer and chemical exposure is controversial. Men whose work involves heavy labor and those exposed to certain metals and chemicals, including cadmium, dimethylformamide, and acrylonitrile, may be at higher risk for prostate cancer. Some studies have indicated that farmers might be at higher risk.

A 2001 study of data collected between 1979 and 1985 concluded that certain leisure activities may expose men to the same chemicals as those that pose a possible danger in the industrial setting. They included:

• Home or furniture maintenance
• Painting, stripping, or varnishing furniture
• Activities that involved exposure to lubricating oils or greases, metal dust, or pesticides or garden sprays

Infection and Inflammation

Scientists think that specific genes that affect the body's response to viruses may be associated with certain types of prostate cancer. Some theories suggest that there may be a relationship between prostate cancer and infections such as herpesvirus, human papillomavirus, and cytomegalovirus. In 2006, scientists identified a new virus, XMRV, which is 30 times more common in men with prostate cancer who have a genetic mutation with the HPC1 gene. Scientists know that men who have the HPC1 genetic mutation are more likely to get prostate cancer. This new research suggests that the genetic mutation may make them more vulnerable to a virus that causes the cancer. Researchers will continue to investigate XMRV and other possible infectious causes of prostate cancer.

Other Factors Associated with Prostate Cancer

Obesity. Obesity may increase the risk for prostate cancer, particularly more aggressive forms of the disease. Obesity may also make prostate cancer more difficult to diagnose. A 2005 study found that overweight and obese men were more likely to be diagnosed with advanced prostate cancer and to die of the disease than normal-weight men.

Nonmelanoma Skin Cancers and Sunlight. One study reported that patients with prostate cancer and a history of nonmelanoma skin may have a higher risk for a poorer outlook. Such skin cancers are highly associated with exposure to sunlight. It should be noted, however, that sunlight triggers production of vitamin D in the body, which may help protect against prostate cancer. Prostate cancer rates are, in fact, lower in southern, sunny regions.