Male circumcision may not make much difference to overall male HIV incidence in Caribbean context

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A cross-sectional study of men attending a large HIV/STI clinic in San Juan, Puerto Rico, has found that, without adjusting for other factors, self-reported HIV and STI prevalence was actually higher in circumcised than in uncircumcised men.

The researchers conclude: “There is a need to apply caution to the use of circumcision as an HIV prevention strategy, particularly in areas like the Caribbean where more effective combinations of strategies for...prevention have yet to be fully implemented.”  

Similar findings from a survey in Zimbabwe (see page 215 of this report), which found an HIV prevalence of 14% in circumcised men and 12% in uncircumcised men recently, reignited controversy as to whether voluntary medical male circumcision (MMC) had a legitimate part to play in HIV prevention programmes.   


voluntary male medical circumcision (VMMC)

The surgical removal of the foreskin of the penis (the retractable fold of tissue that covers the head of the penis) to reduce the risk of HIV infection in men.


The surgical removal of the foreskin of the penis (the retractable fold of tissue that covers the head of the penis) to reduce the risk of HIV infection in men.

statistical significance

Statistical tests are used to judge whether the results of a study could be due to chance and would not be confirmed if the study was repeated. If result is probably not due to chance, the results are ‘statistically significant’. 


Receptive anal intercourse refers to the act of being penetrated during anal intercourse. The receptive partner is the ‘bottom’.


The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

A deeper analysis of the Puerto Rico study shows, however, that circumcised men were 38% more likely to have had recent sex with men than uncircumcised men, and were two to three times more likely to have had unprotected anal sex without a condom.

Although the study cannot determine why this should be, it may be related to the fact that circumcised men were more than three times more likely to come from mainland USA than uncircumcised men and, as the researchers point out, “Puerto Rico is a primarily Christian society with strong prohibitions against sexual contact between men.”

In other words, US-born immigrants may be more likely to be openly gay and/or to have had the chance to have sex with other men than Puerto Rican natives – and were also more likely to be circumcised.

The study

The study interviewed 660 men randomly selected from the waiting room of the largest HIV and STI treatment centre in the city of San Juan in Puerto Rico, between October 2009 and December 2011. The study was questionnaire-based, and all data on STI and HIV prevalence/experience was provided by self-report, as was circumcision status.

The average age of the men was 37, and 84% were born in Puerto Rico. However, while only 3.8% of uncircumcised men came from mainland USA, 12.6% of circumcised men did.

The only other statistically significant demographic difference between circumcised and uncircumcised men was that the latter were 57% more likely to have left school before the age of 15.

Self-reported HIV prevalence in the men was high, at 37% (243 out of 660 respondents), reflecting the fact that this was an HIV and STI clinic. Circumcised men were 21% more likely to have HIV than uncircumcised men (prevalence, 43.0% versus 33.9%). They were also 10.5% more likely to report ever having had an STI. In terms of individual STIs, only genital warts were significantly more common in circumcised than uncircumcised men (prevalence, 18.8% versus 12.2%).

Just under 30% of the men reported every having had sex with another man, with 34% of the circumcised and 28% of the uncircumcised men reporting this. Slightly more men reported being behaviourally bisexual than exclusively gay, in terms of lifetime experience.

In terms of recent sexual experience (meaning within the last three months), however, having had sex with both men and women was quite rare with only 3% of circumcised and 1.8% of uncircumcised men reporting it. In contrast, 30.9% of circumcised and 22.4% of uncircumcised men reported exclusively having had sex with men in the last 90 days. This 38% difference in risk behaviour between circumcised and uncircumcised men was not statistically significant, however (p=0.129).

Sixty per cent of all men reported ever having had unprotected vaginal sex and 9.1% reported having unprotected anal sex with women. Unprotected vaginal sex was 27% more likely in uncircumcised men, whereas unprotected anal sex was not associated with circumcision status.

Only a relatively small minority of men had had unprotected anal sex with another man, with 5.8% saying they had had unprotected anal sex as the insertive partner and 3.6% as the receptive partner. However, there were big differences in circumcision status in these groups. Eight per cent of circumcised versus 4.7% of uncircumcised men had had insertive unprotected anal sex, and 6.5% of circumcised versus 2.2% of uncircumcised men had had it as a receptive partner. Although absolute numbers were small – only 24 out of 660 men admitted to unprotected receptive anal sex – this threefold difference between circumcised and uncircumcised men was statistically significant (p=0.025).  


Without further analysis, it is difficult to say if these behavioural and demographic differences fully explain the unexpectedly higher HIV and STI prevalence in circumcised men, or whether other factors are at play, such as whether men started having sex before or after they were circumcised (the authors assume most men were circumcised as children).

However, this study is an interesting example of how cross-sectional studies can be influenced by demographic and behavioural differences between two groups being compared, in this case circumcised and uncircumcised men.

The authors point out, nonetheless, that a blanket rollout of an MMC programme in the context of a Caribbean country such as Puerto Rico would not necessarily make much difference to HIV prevalence in men as a whole. They argue that traditional measures such as condom promotion and behaviour change may have been under-promoted in this conservative and Catholic territory.

Given that there is no data on the efficacy or otherwise of MMC in anal intercourse, with either men or women, the study may show that for MMC to be useful anywhere other than in the high-prevalence, heterosexually driven epidemics of Africa, it may need to be targeted, at least until more data comes along, at men who exclusively have vaginal sex with women.  


Rodriguez-Diaz CE et al. More than foreskin: circumcision status, history of HIV/STI, and sexual risk in a clinic-based sample of men in Puerto Rico. Journal of Sexual Medicine, early online publication. doi: 10.1111/j.1743-6109.2012.02871.x, 2012.