A Californian study of recently HIV-infected men who have sex with men (MSM) has found that these men were more likely to have unprotected anal sex when they used recreational drugs – especially methamphetamine (crystal meth) – and erectile dysfunction drugs like sildenafil (Viagra).
Enough studies have looked at this issue that there is now a clear association between unprotected anal intercourse (UAI or ‘barebacking’) and recreational drug use. ‘Association’, however, only means that these behaviours frequently go together: i.e., in general, men who use methamphetamine (crystal meth) are more likely to bareback. This does not mean that meth use causes unprotected sex. The exact relationship between drug use and sexual behaviour may be more complicated, and studies to date have not fully explained that relationship.
In this study published in the November 1st edition of the Journal of Acquired Immune Deficiency Syndromes, researchers used different kinds of analyses to shed more light on how drug use affected individual men’s sexual behaviour. They found that men were more likely to bareback at times when they were using methamphetamine or other substances than at times when they were not.
The researchers (based out of University of California, San Diego, and other centres in San Diego and Los Angeles) looked at 194 men who had had sex with other men in the last year. The men were an average of 35 years old, mostly white (nearly 70%), mostly gay (94% - the remainder had had sex with men and women), and well-educated (about 48% had college or higher education). All were recently HIV-infected (an estimated average of four months since infection). This recently-infected group was of particular interest, both because they had probably recently engaged in risky sex, and because viral loads tend to be high in recently-infected individuals, making them more likely to infect others.
Participants provided detailed information about their last three sexual partners, including the kind of sex they had and which drugs (if any) they had used. (Alcohol use was not measured, and no conclusions about the riskiness of alcohol use could be drawn.) Drug use was generally high: 58% had used some sort of drug in at least one sexual encounter, 31% had used crystal meth, 32% poppers (nitrites), 25% marijuana, 13% GHB, and a few had used other drugs. Twenty-three percent had used ‘erectile dysfunction’ drugs – sildenafil (Viagra), vardenafil (Levitra), or tadalafil (Cialis).
The researchers then divided the men into groups, according to whether they had had unprotected intercourse with all (24%), some (60%), or none (16%) of their last three partners. Recreational drug use was lowest in those who had not barebacked at all, and highest in those who had barebacked with all of their most recent partners. Erectile dysfunction drug use, however, was nearly the same in all groups.
The most unique component of the study was an analysis of the men who had only barebacked some of the time, to see the differences between their ‘safe’ and ‘unsafe’ sexual encounters. Recreational drugs were much more commonly used during the ‘barebacking’ encounters – especially crystal meth (5.3 times more common), marijuana (5.7 times), multiple drugs (3.8 times), and poppers (2.6 times).
And the use of marijuana and nitrites?
Other studies have been inconclusive on whether marijuana is associated with greater sexual risks. In this study, although a relationship was found between marijuana use and barebacking, the researchers state that “more than half of marijuana users also used methamphetamine, suggesting that associations between UAI and marijuana may be an artifact of the overlap” – i.e., not truly due to marijuana use itself.
Despite the increased use of nitrites in ‘bareback’ encounters, researchers found the association “ambiguous”: “Lack of association between UAI and nitrite use has been demonstrated previously… nitrites may be less likely to contribute directly to UAI than other substances.”
Methamphetamine use associated with unprotected sex
The researchers stated that, “In all analyses, the most important predictor of UAI [‘barebacking’] among the last three sexual partners was methamphetamine use, suggesting that methamphetamine is an independent predictor of HIV transmission. To our knowledge, our study is the first to demonstrate that methamphetamine is associated with UAI among recently HIV-infected MSM [men who have sex with men], while controlling for individual factors… Considering the high transmissibility of HIV during early infection, these analyses suggest that methamphetamine may contribute significantly to HIV transmission from newly infected MSM to others.”
Conclusion
The researchers concluded that their study “contributes to the overall understanding of drug use and UAI by (1) providing support to prior studies that demonstrate associations between methamphetamine or [erectile dysfunction drugs] and sexual risk behavior, (2) clarifying that a direct association is likely to exist between specific drugs and UAI, and (3) providing evidence that the use of methamphetamine, [erectile dysfunction drugs], and possibly other illicit substances may contribute to HIV transmission.”
A role for erectile dysfunction drugs?
Curiously, the researchers found that erectile dysfunction drugs were much more commonly used for unprotected than for protected sex (13.8-fold), but only with the person’s main sexual partner (boyfriend, life partner), not with other (‘casual’) partners. The researchers also point out that erectile dysfunction drug use likely varies depending on sexual role (insertive or ‘top’ vs. receptive or ‘bottom’ partner) – since receptive partners do not necessarily need to be concerned about having an erection – but they did not have enough data to explore this issue further.
Drumright L et al. Unprotected anal intercourse and substance use among men who have sex with men with recent HIV infection. J Acquir Immune Defic Syndr. 43(3): 344-350, Nov 1 2006.