Might circumcision benefit gay men?

Most of the evidence suggests that circumcision is unlikely to reduce HIV transmission between gay men. This is not unexpected, as more HIV is likely to be acquired rectally than via the penis, but there is little evidence that even ‘tops’ who exclusively practise insertive sex (or claim to) are likely to benefit as a group, though there could be benefit on an individual level.

The HIV Network for Prevention Trials Vaccine Preparedness Study enrolled 3257 gay men in six US cities from 1995 to 1997.¹ This was a longitudinal study, and HIV incidence was 1.55 per 100 person-years over 18 months of follow up. In this study, uncircumcised gay men were twice as likely to become infected with HIV as circumcised men.

However, this was not a randomised controlled trial and, although the results were suggestive, it could not rule out differences in behaviour between circumcised and uncircumcised men as the cause.

One 2001 study² explored the relationship between circumcision and HIV transmission in gay men in Sydney, Australia. Between 1993 and 1999, 74 gay men were interviewed soon after being diagnosed with recent infection. Infection assumed to be through insertive sex comprised 15% of all infections. The researchers found no association between circumcision status and infection by insertive unprotected anal intercourse.

A longitudinal Australian study of 1427 initially HIV-negative gay men suggests that circumcision does not alter HIV incidence in gay men.³ At enrolment, 66% of cohort participants were circumcised. There were 49 seroconversions among cohort participants within the following five years: 29 (69%) in circumcised men and 13 in uncircumcised men, representing an incidence of 0.80 per 100 patient-years. There was no difference in the incidence of HIV infection between circumcised and uncircumcised men. This remained true when the analysis controlled for age, anorectal STIs, and insertive or receptive unprotected anal intercourse (UAI) with someone who was HIV-positive. The incidence in men who reported no receptive UAI was halved (0.35 infections per 100 patient years), but this was not statistically significant.

Another 2007 study from the United States⁴ found no statistically significant evidence that being circumcised protects against HIV infection amongst black or Latino men who have sex with men (MSM), even amongst MSM who said they only practised insertive intercourse. This study interviewed 1079 black and 957 Latino MSM in New York, Philadelphia, and Los Angeles. They found that 74% of black MSM were circumcised and 33% of Latino MSM.

There was no statistically significant association between circumcision and HIV status among Latino MSM (adjusted odds ratio [AOR] = 1.10, 95% confidence interval [CI]: 0.73 to 1.67) or black MSM (AOR = 1.23, 95% CI: 0.87 to 1.74).

The investigators note: “Circumcision conferred neither risk nor protection among black men or Latino men in our study, however, and was unrelated to seroconversion among MSM who reported that their last HIV test was negative. Further, there was no evidence that circumcision was protective among men who had only engaged in unprotected insertive anal sex in any of the models.”

A later meta-analysis of studies of circumcision in gay men and men who have sex with men (MSM) by the same researchers found a small reduction in the risk of HIV infection in circumcised men, but this was not statistically significant.⁵

The meta-analysis covered 17 studies conducted between 1989 and 2007. The analysis also included some unpublished results. The studies included 27,816 circumcised and 25,751 uncircumcised men. Nine were conducted in North America,  while four out of the other eight were conducted in developing countries in Asia and South America. Circumcision prevalence in individual studies varied from 4% to 88%.

Overall, the studies reported a non-statistically significant reduction of 14% in HIV infection for circumcised men. A subset of studies that looked at results in 2238 men who only had insertive sex found a 29% reduction in HIV infection among circumcised men, but this difference was also not statistically significant.

However, in studies conducted prior to the introduction of effective HIV treatment, the authors found a statistically significant 53% reduction in HIV infection in circumcised men. They pointed out that this reduction was “comparable” to that seen in the randomised controlled trials of circumcision in heterosexual men. In contrast,   there was no association whatsoever between circumcision and HIV in more recent studies. The authors also found a non-statistically significant reduction of 51% in HIV infections in circumcised men in studies conducted in developing countries, where antiretroviral therapy is less available.

The authors suggested that higher rates of unsafe sex and resultant HIV and STI infection in gay men since HIV treatment became available may have obscured the relatively small benefit of circumcision.

They also found a trend to more statistically significant results as study quality increased, with a non-significant 32% reduction in HIV infection in circumcised men seen in studies where circumcision and HIV infection were confirmed by genital examination and testing.

A separate editorial⁶ urged further trials to settle the question of whether circumcision offers any protection against HIV to gay men once and for all. The authors commented that: “only further research can answer…the question as to whether MSM should be circumcised to reduce their HIV risk.”

However, they also expressed concerns that such research might face opposition.

“The meta-analysis”, they say, “is likely to be used by both advocates and detractors of clinical trial investment; some will argue that the likely benefit is too modest to justify a multimillion dollar trial while others will argue that only a clinical trial will answer this important HIV prevention question.”