HIV prevalence is four times higher in gay and bisexual men who inject drugs, compared to heterosexual, male, injecting drug users, UK investigators report in Sexually Transmitted Infections. The study also showed that prevalence of infection with the hepatitis C virus was significantly higher among gay and bisexual male injecting drug users (IDUs).
The investigators believe that the higher HIV prevalence seen in gay and bisexual IDUs was due to sexual transmission of the virus. However, the higher rate of hepatitis C is largely attributed to sharing injecting equipment. The study showed that gay and bisexual men were significantly more likely to report unsafe injecting practices than heterosexual men.
Studies conducted in the US and Brazil have previously shown higher prevalence of HIV and hepatitis C in gay and bisexual men who inject drugs compared to heterosexual male IDUs. Investigators wished to see if this was also the case in the UK.
They therefore analysed data from national surveys of injecting drug users conducted between 1998 and 2007 in England, Wales and Northern Ireland. To be included in the current analysis, people had to be aged between 15 and 60 years and to have both had sex and injected drugs in the previous twelve months. Prevalence of HIV and hepatitis C in the participants was determined using anonymous oral antibody tests. Participants also completed a brief questionnaire covering demographic information and sexual and drug use risk behaviours.
A total of 8671 male injecting drug users were included in the study. Overall, prevalence of HIV was 1%; 33% of participants were infected with hepatitis C. Just over half the participants (53%) reported ever having had an HIV test. A large proportion of people with HIV (39%) were unaware they were infected with the virus.
The prevalence of both infections was significantly higher in London compared to other regions.
Sex with another man in the preceding twelve months was reported by 4% of men. This proportion was unchanged over the ten years of the study. Most of the men who reported sex with men also reported sex with women (79%).
Prevalence of HIV infection was significantly higher in gay and bisexual men than heterosexual men (3.2 vs 0.79%; p < 0.001). Gay and bisexual men also had a higher prevalence of hepatitis C virus infection (43 vs 32%; p < 0.001). The prevalence of co-infection was slightly higher in gay and bisexual men, but not significantly so (0.63 vs 0.48%).
Higher-risk sex was reported by three-quarters of gay and bisexual injecting drug users compared to 40% of heterosexual IDUs. Sharing of injecting equipment was also more common among gay and bisexual men than heterosexual men (38 vs 27%; p < 0.001).
Gay and bisexual men and heterosexual men were of a comparable age (approximately 29 years) and had been injecting drugs for a similar length of time (seven years).
Prevalence of HIV (p = 0.046) and hepatitis C (p < 0.001) were higher in those who reported injecting both opiates and stimulants. Prevalence of the infections also increased with age and number of years of injecting.
The investigators calculated that gay and bisexual IDUs were four times more likely to be infected with HIV than heterosexual IDUs (adjusted OR = 4.08; 95% CI, 1.9-8.5).
Gay and bisexual men were approximately one-third more likely to have hepatitis C infection than heterosexual men (adjusted OR = 1.34; 95% CI, 1.1-1.8).
The low level of hepatitis co-infection among HIV-infected gay and bisexual injecting drug users suggested to the investigators that HIV was largely sexually transmitted in this group.
In contrast, they believe that the main mode of hepatitis C transmission in these men was injecting drug use. They found that gay and bisexual men were significantly more likely to report sharing injecting equipment in the previous four weeks than heterosexual men (adjusted OR = 1.72; 95% CI, 1.3-2.2). However, they do not rule out the possibility of sexual transmission of this virus.
“MSM [men who have sex with men]-IDUs in the UK are at a greater risk of blood-borne viral infections than MSW [men who have sex with women]-IDUs,” comment the authors. They conclude that their findings show a need to explore “the impact of the overlap of injecting drug use and sex between men on the HIV epidemic in the UK. They also emphasise the need for more public health research on the health needs and risk behaviours of MSM-IDUs.”