Circumcision does not increase men's risk behaviour in Kenyan trial

A substudy of the randomised controlled trial (RCT) of male circumcision as an HIV prevention method in Kisumu, Kenya has found that there were virtually no differences in risk behaviour or in STI infections between circumcised and uncircumcised men. The trial also found that risk behaviour and STI infection decreased substantially amongst both intervention and control groups during the study.

The Kisumu trial was one of three RCTs of circumcision which were halted early by the data and safety monitors because they had already shown that circumcision substantially reduced the risk of HIV acquisition – see this report. In the case of the Kisumu trial, circumcised men were nearly half as likely as uncircumcised men to catch HIV.

Some public health advocates and political leaders have been reluctant to endorse circumcision for fears that its benefits will be negated by increased risk behaviour by men who perceive that their risk of HIV has been reduced.

This has generally not been borne out by evidence from the RCTs, but there was a hint in preliminary analyses from the Kisumu trial that, though the proportion of men with more than two partners decreased among both groups during the study, it did not continue to decline after six months in circumcised men, but continued to do so in uncircumcised men.

There was no evidence of this in the substudy, where figures for this variable were near-identical between intervention and control groups at the 12-month follow-up.

This study enrolled 1319 out of 1780 eligible RCT participants, 620 in the intervention group and 689 in the control group. In the original RCT questions were asked about five measures of sexual risk behaviour. In the substudy, this was expanded to 18 measures of risk behaviour. The men were also asked about whether they believed circumcision reduced their risk of acquiring HIV and whether this correlated with risk behaviour, and measured the incidence of acute STIs (gonorrhoea, chlamydia and trichonomiasis). Men were presumed to be STI free at the start of the study as all were treated for prevalent STIs before randomisation. The behavioural surveys and STI tests occurred at one, three, six and twelve months after the start of the study.

There were a few differences between the circumcised and uncircumcised men in this substudy. The only one likely to affect the findings was that more men in the circumcision group had an STI at baseline – 65 (10%) versus 47 (7%).

The primary finding of the study was that there were no statistically significant differences between the proportion of circumcised and uncircumcised men who engaged in any of the 18 risk behaviours at any time point. Circumcised men were also no more likely than uncircumcised to believe that their operation reduced the risk of HIV infection at any time point.

Circumcised men were more likely to be diagnosed with a new STI at the six-month time point (6% versus 3%), but this difference disappeared at 12 months (2% versus 3%). The authors speculate that this might be due to re-infection from partners, who were not treated at baseline.

The 18 risk variables were composited into a Risk Score on a scale from zero (no sex at all since the last visit) to nine (highest risk on all variables). This risk score fell substantially for both circumcised and uncircumcised men during the study, from 3.55 in uncircumcised men and 3.25 in circumcised men at baseline to 2.5 for both groups at twelve months. In practical terms this meant that at the 12 month follow-up men were 59% less likely to report not having any sex, and of those who did, there was a 16% decrease in risk scores. These were statistically significant declines.

STI incidence fell for both groups during the study, and the 45% decline between months six and 12 was statistically significant. Men with a prevalent STI at baseline were three times more likely to catch another one during the study (which may confirm the reinfection theory) and poorer men, who also had lower sexual risk scores, were less likely to catch STIs than richer ones (the dividing line between rich and poor was 2000 Kenyan shillings (£15.78) a month).

Individual variables for which there was a particularly significant decrease (or, in the case of circumcision beliefs, increase) include the following:

All figures in per cent.

* The definition of concurrent partnerships was an overlap of at least one month between regular partners.

† p = 0.02 †† p = 0.05. No other differences statistically significant.

Men who were married or cohabiting were unsurprisingly more likely to engage in any sexual activity, but perhaps more surprisingly, had only marginally higher risk scores. There was no relationship between believing that circumcision reduced the risk of acquiring HIV and any sexual risk factor.

This substudy included about half the total number of men enrolled in the RCT, and its findings are probably representative of behavioural change amongst other participants.

The authors comment that “these are important results in the face of reluctance on the part of some in the international community to endorse male circumcision…[they] provide evidence that risk compensation is likely to be minimal or absent among circumcised men and, therefore, it should not…be considered a barrier to the promotion of male circumcision for HIV and STI prevention.”

Nonetheless, they concede, the participants were only followed for the relatively short period of a year, and the study does not preclude the possibility that circumcised men might slowly start taking more risks in time.

They also point out that participation in the RCT involved repeated HIV testing and individually-tailored risk reduction counselling.

They comment: “Conditions under which [male circumcision] is provided widely are likely to be different”, adding that “it will be necessary to further evaluate the possibility that men increase their HIV risk behaviour after circumcision is offered in more naturalistic public health and medical settings”.

They therefore urge that male circumcision is always offered alongside a full package of HIV prevention methods including HIV testing, STI diagnosis, condom provision, and risk reduction counselling. As long as this is done, they comment, “HIV risk behaviours after circumcision are unlikely to increase. Indeed, they may well decline.”