"This paper identifies a genetic risk factor that about doubles the likelihood of prostate cancer in younger African-American men," says Harvard Medical School Assistant Professor of Genetics David Reich, the lead investigator of the study. "This finding may explain why younger African-Americans have an increased risk for prostate cancer than do other populations -- and may also explain why this increased risk in African-Americans attenuates with older age."

The lead author of the study, Dr. Matthew Freedman, a Harvard Medical School instructor at the Dana-Farber Medical School, said the finding is one of the first genetic risk factors found responsible for an appreciable fraction of sporadic prostate cancer cases.

"Interestingly," said Freedman, "we found that this region also confers risk for prostate cancer for diverse ethnic groups. The actual gene, however, remains to be identified."

The study is detailed in the online early edition of the Proceedings of the National Academy of Sciences.