Cutting HIV by cutting

Yesterday’s Journal of the American Medical Association (JAMA) included an important new study on the effect of circumcision on transmission of HIV, the virus that causes AIDS (Circumcision Status and Risk of HIV and Sexually Transmitted Infections Among Men Who Have Sex With Men A Meta-analysis, Gregorio A. Millett; Stephen A. Flores; Gary Marks; et al. JAMA. 2008;300(14):1674-1684 ). The study adds information to our understanding of how HIV is transmitted and what we can do to reduce the spread of the virus. Unfortunately, lay publications misrepresented the findings of the study, calling the value of circumcision into question.

 The new study does not change what we already know: circumcision dramatically reduces the risk of transmitting HIV. The new study merely shows that the protective effect, which is quite strong among heterosexual men, does not extend to gay men having certain forms of sex.

 The protective effect of circumcision was discovered by epidemiological data. Studies of the incidence and prevalence of HIV among heterosexual African men revealed that circumcision is associated with a statistically significant protective effect against HIV. However, correlation is not causation, and large scale controlled studies were done to determine if circumcision really does prevent the transmission of HIV. The accompanying editorial in JAMA explains:

Adult male circumcision reduced HIV acquisition among … heterosexual men in South Africa, Kenya, and Uganda with effect sizes that were remarkably consistent and similar to those predicted by the earlier observational studies. The biological plausibility of HIV protection resulting from male circumcision has been supported further by … studies indicating the susceptibility of the inner foreskin for virus-target cell contact… [C]ircumcision was determined to protect against HIV in high-quality, well powered clinical trials in 3 different nations of Africa. Based on the biological, histopathological, epidemiologic, and clinical trials evidence, global health leaders now promote circumcision for reducing HIV risk in heterosexual men.

 The new study sought to answer a different question. Does circumcision protect against HIV transmission in among men who have sex with men (MSM)? We know that circumcision prevents transmission of HIV in vaginal intercourse, but does it offer the same protective effects in other forms of sex? Unfortunately, to date there have been no studies that specifically address this issue. Therefore, the authors of the JAMA study reviewed studies done for other purposes from 1989-2008 to see if they could find any information about circumcision and gay sex.

 The authors reviewed thousands of studies on circumcision but were only able to find 15 that had recruited gay men, used circumcision as a study variable, and tested for HIV status. Keep in mind though that none of the studies were focused on the effect of circumcision on the transmission of HIV among gay men. The authors describe the studies:

The 15 studies were conducted between 1989 and 2007… The average quality of the studies … was moderate. Five studies that met 5 or more study quality criteria were considered the highest quality; the remaining studies fulfilled fewer than 5 of the scale’s 8 study criteria… A total of 53 567 MSM were included in our analytical sample, 52% of whom were circumcised.

 When the authors pooled the data from these 15 studies, they found:

… a protective, albeit statistically nonsignificant, association of circumcision with HIV infection in our metaanalysis of MSM observational studies …Our data revealed that male circumcision conferred a significant protective effect from HIV infection among MSM in studies conducted before [retroviral drug therapy] but not after, possibly due to documented increases in sexual risk behavior during the era since the availability of [retroviral drug therapy].

 In other words, the review of these 15 studies could not answer the question of whether circumcision is as effective in preventing the transmission of HIV in gay men as it is in heterosexual men. Where does that leave us? According to the accompanying editorial:

… [I]s further research warranted to evaluate the effect of circumcision on HIV incidence in MSM? Most scientists and policy makers will argue a vigorous yes, because MSM continue to be disproportionately over represented in new HIV cases …There is a global need to know whether male circumcision should be considered a tool in the fight against HIV transmission among MSM…

Infant and adult circumcision are recommended in regions with high HIV prevalence as in sub-Saharan Africa. But the question as to whether MSM should be circumcised to reduce their HIV risk, particularly men who preferentially practice insertive sex, is one that only future research can answer.

 Circumcision is still one of the most effective tools in limiting the transmission of HIV. It remains to be seen whether the benefits observed in heterosexual sex will extend to gay sex as well.