Circumcision may protect HIV-negative gay men from syphilis

Circumcision protects HIV-negative gay men from infection with syphilis, Australian investigators report in the December 15^th edition of the Journal of Infectious Diseases. However, circumcision did not affect the risk of acquiring any other sexually transmitted infection.

The study was conducted by investigators from the Health in Men (HIM) study. This is the same group of investigators who recently reported that circumcision may protect gay men with a “preference” for insertive anal sex from HIV.

Gay men are disproportionately affected by sexually transmitted infections and new methods of preventing them are required.

Observational studies conducted in heterosexuals have suggested that circumcision is protective against ulcerative sexually transmitted infections, including genital herpes and syphilis. In addition, the Rakai randomised controlled trial showed that circumcision protected against genital herpes, but not syphilis.

It is not possible to generalise the findings of studies involving heterosexual men to gay men. Therefore investigators in Sydney performed a prospective study involving 1426 gay men to see if rates of prevalent and incident sexually transmitted infections differed according to circumcision status.

Recruitment to the study was conducted between 2001 and 2004 and the men were followed until the end of 2007. All were HIV-negative at baseline.

The men’s circumcision status was determined by a physical examination on entry to the study.

Every six months, the men had follow-up interviews when they reported their most recent sexual behaviour. They also had annual sexual health check-ups.

Over 5000 person years of follow-up were available for analysis, the average period per patient being 3.9 years.

There was no difference in the prevalence of sexually transmitted infections at baseline between circumcised and uncircumcised men.

However, after controlling for potentially confounding factors such as age and number of receptive acts of unprotected intercourse, the circumcised men had a significantly reduced risk of acquiring infection with syphilis (p = 0.019).

The protective effect of circumcision against incident infection with syphilis was strengthened when the investigators restricted their analysis to men who expressed a preference for the insertive role during anal sex (p = 0. 033).

Circumcision did not reduce the risk of any other infections.

“Circumcised participants in the HIM cohort were at significantly reduced risk of incident syphilis infection”, write the investigators.

They do not believe, however, that circumcision is likely to have “a substantial public health impact in reducing acquisition of most sexually transmitted infections in homosexual men.”