Men who are circumcised may be more protected against persistent infection with the virus that causes genital warts, a new study suggests.
The study, which followed 285 men ages 18 to 44, found that among those who became infected with the human papillomavirus (HPV), circumcised men were more likely to have their immune systems "clear" the virus by the end of the 18-month study.
When it came to the risk of acquiring the virus in the first place, the biggest risk factor was having a large number of lifetime sex partners, the researchers report in The Journal of Infectious Diseases.
There are more than 100 strains of HPV, some of which cause genital warts. In most people, the immune system clears the infection fairly rapidly. However, persistent infection with certain HPV strains can eventually lead to cancer.
Persistent HPV infection is the primary cause of cervical cancer, but it can also lead to cancers of the anus and the penis in men.
Compared with women, little is known about men's risk factors for HPV infection — or the factors that affect their ability to clear the virus, according to the principal researcher Dr. Anna R. Giuliano of the H. Lee Moffitt Cancer Center and Research Institute in Tampa, Florida, and her associates.
To investigate, they followed 285 men for about 18 months, testing for HPV every 6 months. Overall, 29 percent of the men became infected with the virus over 1 year; 19 percent acquired an HPV strain linked to cancer.
Men who said they'd had more than 16 sex partners had about three times the HPV risk of those with fewer sex partners. They were also nearly 10 times more likely to contract a potentially cancer-causing strain.
When it came to HPV clearance, circumcision appeared beneficial, the researchers found.
Circumcised men were three times more likely to clear any type of HPV infection by the end of the follow-up period and six times more likely to clear a cancer-linked HPV strain.
The reasons for these findings are not clear, according to Giuliano and her colleagues. It's possible, they suggest, that circumcised men are less likely to get skin abrasions during sex, which might mean that fewer HPV particles enter their bodies.
SOURCE: The Journal of Infectious Diseases, February 1, 2009.