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

Disclosures

AIDS. 2009;23(2):243-252. 

In This Article

Results

A total of 1427 participants were enrolled between June 2001 and December 2004. The median age at enrolment was 35 years, ranging from 18 to 75 years. The great majority (95.2%) of participants self-identified as gay or homosexual. Follow-up interviews at 1 and 2 years were attended by 87 and 81% of participants, respectively, and the main reason for loss to follow-up was participants relocating from Sydney (n = 139, 9.74%).

There were 53 HIV seroconversions, an overall HIV incidence of 0.78 per 100 person-years (95% CI 0.59-1.02). The median age at HIV seroconversion was 37 years (range 22-63). The total follow-up time for risk factor analysis was 5161 person-years, and the median was 3.9 years per participant. Risk factor analysis was performed on 47 HIV seroconverters for whom sexual behaviour data were available within 12 months of seroconversion.

None of the demographic factors examined, including age (P trend = 0.825), education (P trend = 0.336), current income (P trend = 0.700) and occupational level (P = 0.253) were related to the risk of HIV infection.

In univariate analysis, all nine modes of UAI with regular and casual partners combined were significantly related to HIV acquisition ( Table 1 ). Similar patterns were observed when these analyses were separated by partner type (Appendix Table A1). There were seven seroconversions in men who reported no UAI in the seroconversion interval, but in each participant, UAI was reported in the 6-month period immediately prior. In the multivariate model, only UAI-R with withdrawal with HIV status unknown partners and UAI-R with ejaculation with HIV-positive partners remained significantly associated with HIV infection ( Table 1 ).

Serosorting. Overall, 38.0% of total follow-up and 29.8% of all infections (n = 14) occurred in men who reported that all their UAI was with partners they believed were HIV negative. Compared with men who reported no UAI, these men were at more than twice the risk of HIV infection, but this did not reach statistical significance ( Table 2 ). However, compared with those who reported UAI with HIV-positive partners, they were at significantly reduced risk of HIV infection (hazard ratio = 0.13, 95% CI 0.06-0.29).

Men who were classified as serosorters were classified into three mutually exclusive categories as outlined in Table 3 . The first category was men who met the criteria for negotiated safety. Overall, 24.7% of total follow-up and 14.9% of all infections (n = 7) occurred in these men. Their risk of HIV infection was not significantly greater than those who reported no UAI. The second category was men who reported UAI with an HIV-negative regular partner that could not be classified as negotiated safety, but no UAI with casual partners. Overall, 9.0% of total follow-up and 10.6% of all infections (n = 5) occurred in men in this category, and these men were at significantly higher risk than those who reported no UAI. The third category was men who reported UAI with casual partners who were reported to be HIV negative. Overall, 4.2% of total follow-up and 4.3% of all infections (n = 2) occurred in men in this category. Compared with men who reported no UAI, these men were at three-fold increased risk, but this did not reach statistical significance.

Strategic Positioning. Overall, 15.3% of total follow-up and 8.5% of all infections (n = 4) occurred in men who reported their highest risk behaviour was insertive UAI. Compared with men who reported no UAI, these men were not at significantly increased risk of HIV infection ( Table 2 ). Overall, men who reported insertive UAI only were at significantly lower risk of HIV infection than men who reported any receptive UAI (hazard ratio = 0.32, 95% CI 0.12-0.91).

Withdrawal. Overall, 36 infections (76.5% of all infections) were in men who reported receptive UAI. A substantial proportion of these were in men who reported their highest risk behaviour was receptive UAI with withdrawal (n = 11, 23.4% of all infections and 12.8% of total follow-up). Compared with men who reported no UAI, men who reported withdrawal were at five-fold significantly increased risk of HIV infection ( Table 2 ).

Combined HIV Risk Reduction Behaviours. Overall, men who reported any risk reduction behaviour were about three times more likely to seroconvert to HIV than men who reported no UAI, but they were much less likely to become infected than men who reported UAI without risk reduction ( Table 2 ). Patterns of sexual positioning were clearly different depending on the reported serostatus of partners (Figure 1). Men who reported UAI with HIV-negative partners only were much less likely to report UAI-R with withdrawal [odds ratio OR = 0.52, 95% CI 0.43-0.63] or strategic positioning (OR = 0.44, 95% CI 0.36-0.54). Among men who reported that all their UAI partners were HIV negative, most (64%) risk periods included UAI-R with ejaculation. UAI-R with ejaculation with HIV-negative partners was associated with a higher risk of HIV infection compared with men who reported no UAI (hazard ratio = 2.87, 95% CI 1.13-7.29; Table 4 ). On the contrary, in men who reported UAI with HIV-positive partners, most (56%) risk periods were of insertive only UAI and only 11% included any UAI-R with ejaculation.

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.

Among those men who reported any UAI with HIV-positive partners ( Table 4 ), both insertive only UAI and withdrawal were associated with reduced risks of HIV infection compared with UAI-R with ejaculation (hazard ratio = 0.14, 95% CI 0.04-0.50; and hazard ratio = 0.16, 95% CI 0.04-0.63, respectively), although in both cases, incidence of HIV was significantly higher than no UAI (hazard ratio = 9.09, 95% CI 2.65-31.22 for insertive only UAI, and hazard ratio = 10.22, 95% CI 2.64-39.61 for withdrawal).

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