Unprotected Anal Intercourse, Risk Reduction Behaviours, and Subsequent HIV Infection in a Cohort of Homosexual Men

Fengyi Jin; June Crawford; Garrett P Prestage; Iryna Zablotska; John Imrie; Susan C Kippax; John M Kaldor; Andrew E Grulich


AIDS. 2009;23(2):243-252. 

In This Article


Receptive UAI remains the main mode of HIV transmission in homosexual men. UAI was very common in this cohort, being reported during 60% of total follow-up periods. However, in only 7% of total follow-up, did this UAI occur where consistent risk reduction behaviour was not observed. Two of the four HIV risk reduction behaviours examined, negotiated safety and strategic positioning, were not associated with significantly increased HIV incidence compared with no UAI. The other two were somewhat less effective. First, serosorting with regular partners outside of negotiated safety, or with casual partners, was associated with HIV infection rates about three-fold higher than those who reported no UAI. Second, withdrawal was associated with a five-fold increased risk of HIV seroconversion, but this was confounded by the fact that it was commonly practised with HIV-positive partners. Among those whose UAI partners were HIV positive, withdrawal was associated with a lower risk than UAI-R with ejaculation. Thus, each of the risk reduction behaviours examined was associated with a HIV incidence that was intermediate between that in those who reported no UAI, and UAI without that form of risk reduction behaviour.

Serosorting was described initially as a risk reduction strategy in HIV-positive homosexual men.[13,14] In HIV-negative men, the effectiveness of this strategy in HIV prevention will be compromised in any setting where there is uncertainty about the actual HIV status of the sexual partner. Negotiated safety is likely to be a setting where there is relative certainty of the HIV-negative status of the partner,[15,16] and this strategy is commonly practised among homosexual men in established relationships.[26,27,28] The Health in Men (HIM) study has confirmed that negotiated safety, applied consistently, can substantially protect men from becoming HIV infected. On the contrary, HIV incidence was higher in those men who practised serosorting outside of a negotiated safety agreement. This is not surprising, as accurate knowledge of partner's HIV status is less likely in casual sex or within a recently formed relationship.[29] It is uncertain to what extent these results may apply in other gay community settings. In Sydney, the rate of HIV testing in homosexual men is among the highest in the world, and testing is most frequent in higher risk individuals.[30,31] At screening for entry into the HIM study, only 0.6% of 1435 potential participants wrongly perceived that they were HIV negative.[22] In contrast to this accurate knowledge of HIV-negative status, almost half of men diagnosed with HIV in one US study were unaware they were infected.[32] Knowledge of current HIV status in Sydney appears to be more accurate than in many other settings.[33]

The per-contact probability of HIV transmission of insertive UAI is an order of magnitude lower than for receptive UAI.[34] There is clear evidence that sexual positioning strategies have been adopted by some homosexual men, both HIV negative and HIV positive, when negotiating UAI.[17,35] The term strategic positioning was originally defined as occurring only in non-seroconcordant UAI,[17] but we consider any report of consistent insertive only UAI as strategic positioning. The HIM study has demonstrated that overall, the incidence of HIV in men consistently practising only insertive UAI was no greater than the HIV incidence in those practising no UAI. However, insertive UAI was still associated with a substantial HIV incidence, of almost 3% per year, in those men who practised it with HIV-positive partners. In interpreting these results, it should be noted that the HIM population was predominantly (66%) circumcised,[36] and thus may have been at relatively low risk from insertive sex.

Withdrawal during intercourse is a fallible but common method of birth control in heterosexual couples.[37,38] Among homosexual men, the practice is common,[7] and there is a perception that it is at least partially efficacious in reducing HIV risk.[39] The HIM study has confirmed that there remains a substantial risk of HIV infection in those who consistently practise withdrawal. Nevertheless, among those who reported UAI with HIV-positive partners, the risk of HIV infection was lower than that among those who engaged in UAI-R with ejaculation.

We found that men who reported serosorting were much less likely to report both strategic positioning and withdrawal and were more likely to report UAI-R with ejaculation. In some ways, it is only common sense that strategic positioning be uncommon with HIV-negative partners, as in this setting, UAI will always involve one insertive and one receptive HIV-negative partner. However, the finding that they were less likely to practise withdrawal suggests that they felt they were adequately protected against HIV by serosorting when engaging in UAI-R. In fact, our data showed that serosorters who practised UAI-R with ejaculation were at significantly increased risk of HIV infection compared with those who had no UAI.

A key feature of the analyses we have performed is that we have examined consistent practice of risk reduction behaviours and not conscious intent. Given the direct link between sexual risk behaviour and HIV infection and the complexity of the relationship between intention and behaviour, we believe it is appropriate to examine the association with behaviour. In the future, studies of intent are needed to elucidate the contexts of this decision making. Our definition of risk reduction behaviours was based on exclusive practice. For example, if a man reported multiple episodes of insertive UAI and a single episode of UAI-R during a 6-month period, he was classified as not reporting strategic positioning in that period. Thus, our results can only be generalized to those who successfully apply any intentional strategy. In examining such complex and multilayered behaviours, small subgroups were inevitably created, with consequent limited power. This also prevented us from using a multivariate approach to incorporate other known risk factors. Nevertheless, the HIM study is the first prospective study to report on the effectiveness of the practice of risk reduction behaviours.

This study has demonstrated that consistent practice of risk reduction behaviours is common among homosexual men in Australia, and suggests that each of the risk reduction behaviours examined offered substantial but incomplete protection against HIV infection compared with other patterns of UAI. Having said that, consistent condom use (no UAI) was reported in 40% of the follow-up periods, and this remains the most effective risk reduction behaviour. Our results strongly suggest that policy makers, educators and researchers need to engage with the realities under which UAI is occurring, as well as targeting UAI itself. The relatively low incidence rates of HIV observed in this cohort, despite high overall levels of UAI, and the fact that Sydney is one of very few places in the developed world that has not recently seen an increase in HIV notifications in gay men[33] suggest that risk reduction behaviours can be associated with some success in containing HIV at the population level.


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