It's now clear that circumcision reduces heterosexual men's risk of getting HIV from sexual intercourse. Can circumcision reduce HIV infection rates among men who have sex with men?
To find out, behavioral scientist Gregorio A. Millett, MPH, and colleagues at the CDC's division of HIV/AIDS prevention analyzed data on circumcision and HIV risk from 15 different studies of 54,000 men who had sex with men.
Overall, the data showed a weak effect: a 14% lower risk of HIV in circumcised gay/bisexual men. The finding was not statistically significant. That means even this small benefit could very well be due to chance.
But there was one highly significant finding. Back when AIDS was still a death sentence -- before the 1997 advent of highly effective HIV drugs -- circumcision cut men's risk of getting HIV by 53%.
"There has been an increase in sexual risk behavior in men who have sex with men since the availability of highly effective treatment for HIV," Millett tells WebMD. "If a man is engaged in unprotected sex or has lots of sex partners, that contributes more to his risk of HIV than being uncircumcised. So in recent years, the benefit of circumcision may have been overridden by the risks of unsafe sex."
Of course, that was yesterday. Today the world still struggles to control the spread of the AIDS virus. And there's another key finding from the Millett study.
In the few studies that looked specifically at men who predominantly engaged in insertive anal sex, circumcision seemed to offer more protection. This effect was much stronger in populations where relatively few men are circumcised.
It's a very important issue, says Sten Vermund, MD, PhD, director of Vanderbilt University's Institute for Global Health.
"The prospect that predominantly insertive men might derive considerably more benefit from circumcision is as logical as the day is long," Vermund tells WebMD. "What benefit is a predominantly receptive man going to gain from circumcision?"
Vermund notes that there is good evidence that, in many parts of the world, a high proportion of men who have sex with men are exclusively or predominantly insertive sexual partners. In areas where few men now are circumcised, circumcision could have a powerful effect on HIV transmission -- if it went hand-in-hand with safer sexual behavior.
"To add one more tool to our HIV prevention toolbox -- even if it affects only 40% of a risk group -- would be substantial," Vermund says.
Vermund and Millett agree that a clinical trial to test this approach is needed. Whether such a study can attract increasingly scarce funding is an open question.
The Millett study, and an accompanying editorial by Vermund and colleague Han-Zhu Qian, MD, PhD, appear in the Oct. 8 issue of The Journal of the American Medical Association.