Unprotected anal intercourse, risk reduction behaviours, and subsequent HIV infection in a cohort of homosexual men

Abstract

Objective: A range of risk reduction behaviours in which homosexual men practise unprotected anal intercourse (UAI) has been described. We aimed to assess the extent of any reduction in HIV risk associated with these behaviours.

Design: A prospective cohort study of HIV-negative homosexual men in Sydney, Australia.

Methods: Men were followed up with 6-monthly detailed behavioural interviews and annual testing for HIV. The four risk reduction behaviours (behaviourally defined) examined were serosorting, negotiated safety, strategic positioning, and withdrawal during receptive UAI (UAI-R).

Results: In 88% of follow-up periods in which UAI was reported, it occurred in the context of consistent risk reduction behaviours. Compared with those who reported no UAI, the risk of HIV infection was not raised in negotiated safety [hazard ratio = 1.67, 95% confidence interval (CI) 0.59-4.76] and strategic positioning (hazard ratio = 1.54, 95% CI 0.45-5.26). Serosorting outside negotiated safety was associated with an intermediate rate of HIV infection (hazard ratio = 3.11, 95% CI 1.09-8.88). Withdrawal was associated with a higher risk than no UAI (hazard ratio = 5.00, 95% CI 1.94-12.92). Patterns of UAI differed greatly according to partner's serostatus. Men who reported serosorting were less likely to report either strategic positioning or withdrawal.

Conclusion: Each behaviour examined was associated with an intermediate HIV incidence between the lowest and highest risk sexual behaviours. The inverse association between individual behaviours suggests that men who practise serosorting rely on this protection. The high prevalence of these behaviours demands that researchers address the contexts and risks associated with specific types of UAI.

Fig. 1. Distribution of sexual position during unprotected anal intercourse and reported HIV status of sexual partners (percentage of person-years at risk in each category)

Categories were defined as follows: HIV status of sexual partners: HIV negative = all unprotected anal intercourse (UAI) during a follow-up interval was with sexual partners reported to be HIV negative; HIV status unknown = at least one episode of UAI during a follow-up interval was with a sexual partner reported to be of unknown HIV status, but no episodes were with an HIV-positive partner; HIV positive = at least one episode of UAI during a follow-up interval was with a sexual partner reported to be HIV positive. Sexual position: Insertive only = all UAI during a follow-up interval was in the insertive position; receptive with withdrawal = at least one episode of UAI during a follow-up interval was in the receptive position, with withdrawal before ejaculation, and none was in the receptive position with ejaculation inside the rectum; receptive with ejaculation = at least one episode of UAI during a follow-up interval was in the receptive position with ejaculation in the rectum. (a) Stratified by reported HIV status of sexual partners. (b) Stratified by sexual positioning during UAI.