Reducing the use of poppers in serodiscordant unprotected sexual encounters should be an objective of gay men’s HIV prevention campaigns, according to UK investigators in an article published in the online edition of Sexually Transmitted Infections.
Researchers found that gay men who inhaled poppers during unprotected anal intercourse had a significantly increased risk of being infected with HIV. The investigators think there are two reasons why poppers are implicated in HIV transmission. Firstly, they facilitate longer and 'rougher' sexual intercourse; and secondly, poppers could increase biological susceptibility to infection, either by suppressing immune function or increasing uptake of body fluids.
Unsurprisingly, men who had unprotected receptive anal sex and those who received ejaculate, had an increased risk of acquiring HIV. But the researchers also found that unprotected insertive anal sex, a practice that many men believe to be ‘low risk’ for HIV, in fact involved an increased risk of seroconversion.
Sex between men remains the main focus of HIV transmission in the UK. In 2005, over 2,300 gay men in the UK were newly diagnosed with HIV, accounting for 84% of all infections acquired in the country.
There is evidence of high levels of ongoing HIV risk behaviour amongst gay men in the UK, with almost 50% reporting unprotected sex in the past year in recent nationwide sex surveys. High rates of sexually transmitted infections and the reemergence of syphilis and LGV also show that the sexual health of gay men is a cause for concern.
Cohort studies have shown that receptive anal sex without a condom is the sexual activity with the highest risk of HIV, and reducing the amount of unprotected anal sex between men of different HIV infection status is a specific objective of HIV prevention initiatives in the UK.
In 2001 the INSIGHT research project was established to identify the factors driving new HIV infections on the UK’s gay men.
As part of the project investigators designed a case-controlled study involving gay men recruited between 2002 and 2004 in Brighton, London and Manchester.
Cases were men recently diagnosed with HIV who had had a negative test within the previous two years. Controls were men who tested HIV-negative on both occasions.
A total of 75 men recently diagnosed with HIV and 157 controls were recruited to the study. The men completed a computer-assisted interview to provide details of their sexual and drug use behaviours.
The HIV-positive and HIV-negative men shared demographic characteristics, both having a mean age of 35 years, with 90% being white and 50% educated to degree level.
Between HIV tests 83% of men diagnosed with HIV and 55% of men testing HIV-negative reported unprotected receptive anal intercourse. This was associated with an increased risk of HIV seroconversion (OR, 3.9; 95% CI: 2.0 – 7.7). The more men an individual had unprotected receptive anal intercourse with, the higher the risk of seroconversion (five or more men, OR, 5.27; 95% CI: 2.32 – 11.97).
Men testing HIV-positive were also more likely to report recent unprotected receptive anal sex with a man known to be HIV-positive (28% vs. 11%, OR, 3.2; 95% CI: 1.6 – 6.4). The risk of seroconversion increased if poppers were used during unprotected sex (OR, 9.3; 95% CI: 3.3 – 26.2) and if ejaculation occurred, particularly if there was unprotected receptive sex with more than one man known to be HIV-positive (OR = 6.7; 95% CI: 1.3 – 33.8).
Unprotected receptive sex with partners of unknown HIV status was also a significant risk factor for HIV seroconversion (OR, 4.3; 95% CI: 2.4 – 7.8). Engaging in receptive unprotected sex with regular (OR, 2.4; 95% CI: 1.4 – 4.3) and causal partners (OR, 3.7; 95% CI: 2.0 – 6.8), increased the risk of seroconversion.
Unprotected insertive anal intercourse was also identified as a risk factor for seronconversion.
This risk behaviour was reported by 76% of cases and 61% of controls (OR, 2.1; 95% CI: 1.1 – 3.8). The more men with whom an individual engaged in unprotected insertive sex with, the greater the risk of seroconversion (five or more men, adjusted odds ratio [AOR], 2.3; 95% CI: 1.1- 45.1).
Multivariate analysis showed that rimming (AOR, 3.3; 95% CI: 1.3 – 8.5) and being fisted (AOR, 3.1; 95% CI: 1.4 – 7.0) were activities “underlying” an increased risk of seroconversion. Multivariate analysis also showed that infection with gonorrhoea was associated with an increased risk of seroconversion (AOR, 4.22; 95% CI: 1.82 – 9.74). Gonorrhoea has been shown to increase viral load in the semen of HIV-positive men and this could have facilitated seroconversion to the recently-infected men in this study.
Similar proportions of HIV-positive and HIV-negative men reported recreational drug use, and in the investigators’ initial analysis poppers, ecstasy, ketamine, LSD, and Viagra were all associated with an increased risk of seroconversion. But in multivariate analysis, only poppers use was associated with seroconversion (AOR = 3.5; 95% CI: 1.7 – 7.3). Although approximately 10% of men reported use of methamphetamine, a drug that has been blamed for HIV risk behaviours in the US, the investigators found no evidence that the use of the drug increased HIV seroconversion risk in their sample.
The investigators then turned their attention to where men met their sexual partners. Their initial analysis failed to show any significant relationship between any venue or mode of making contact and seroconversion, but their multivariate model found that men who met their partners on the internet had an significantly increased risk of becoming infected with HIV (AOR, 1.9; 95% CI: 1.0 – 3.4).
In their final set of analysis, the researchers identified unprotected receptive sex with partners not known to be HIV-negative (AOR, 4.1; 95% CI: 1.8 – 9.3), unprotected insertive anal intercourse with more than one man (AOR, 2.7; 95% CI: 1.3 – 5.5) and the use of poppers (AOR, 2.4; 95% CI: 1.1 – 5.2) to be independently associated with an increased risk of seroconversion.
“This study confirms that population level goal…for HIV prevention programmes for gay men should continue to focus on reducing serodiscordant unprotected anal intercourse”, comment the investigators. They also note, “the risk associated with unprotected insertive anal intercourse has also been clearly identified, a practice which many men may mistakenly think low risk.”
As regard poppers use, the investigators conclude, “the attributable risk of nitrite inhalants to HIV seroconversion among gay men in the UK is high and…reduction in their use during HIV serodiscordant unprotected intercourse be adopted as a population level goal/objective by prevention programmes.”
Macdonald N et al. Factors associated with HIV seroconversion in gay men in England at the start of the 21st century. Sex Transm Infect (online edition, published November 14th, 2007).