FRIDAY, March 26 (HealthDayNews) -- Circumcised men may be up to six times less likely than uncircumcised men to be infected by HIV-1, says a study in this week's issue of The Lancet.

The study also found this major difference in risk may be because the foreskin on uncircumcised males is enriched with cells that are targets for HIV-1.

American and Indian researchers studied men coming to sexually transmitted infection (STI) clinics in India. All the men were HIV-negative when first assessed. Most of the men were assessed three times over the course of the year after their initial assessment. While circumcision may help protect against HIV-1, it does not protect against herpes simplex virus type 2, syphilis or gonorrhea, the study found.

"These data confirm previous findings that male circumcision reduces the risk of HIV-1 acquisition. This analysis expands on earlier studies by including laboratory-defined incident STIs as outcomes in the analysis, as well as by including risk behavior to control for other potential differences between circumcised and uncircumcised men," researcher Robert C. Bollinger, from Johns Hopkins University Medical School, says in a prepared statement.

"A unique and important finding from this study was a highly significant and specific protective effect of male circumcision on the risk of HIV-1 acquisition. Our data failed to show a significant protective effect of circumcision on the risk of the other STIs," Bollinger says.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about HIV infection and AIDS.