Prostate cancer has been found to be more frequent and aggressive in young men, according to a new study by the University of Michigan.

Researchers said that prostate cancer rates in young men have increased by six times in the last 20 years.

"Early onset prostate cancer tends to be aggressive, striking down men in the prime of their life. These fast-growing tumors in young men might be entirely missed by screening because the timeframe is short before they start to show clinical symptoms," said Kathleen A. Cooney, M.D., professor of internal medicine and urology, in a statement.

Normally, prostate cancer occurs in men between the age group of 70-80 years. Most of the prostate cancers are slow-growing and many older men diagnosed with early stage of the medical condition eventually die from causes other than prostate cancer.

Researchers said that men with family history of prostate cancer face a two to three times increased risk of developing the cancer and the risk is higher for younger men with several affected relatives.

For the study, the researchers compared the DNA of both normal and cancerous prostate tissue of men diagnosed with advanced prostate cancer before the age of 61 years.

The researchers found that men with early onset of prostate cancer showed more genetic variants when compared to their peers who developed the disease at a later age. They recommend genetic counseling or increased monitoring of younger men with a family history of prostate cancer.

"The unexpectedly poor prognosis of advanced stage early onset prostate cancer supports the idea that a new clinical subtype might exist in the subset of men with early onset prostate cancer," Cooney said.

The finding is published in Nature Reviews Urology.