The HIV epidemic is severe among gay, bisexual and other men who have sex with men (GBMSM) in China, as the overall HIV prevalence and incidence in this group are both high and increasing (9.9% and 5.6 per 100 person-year in 2016) (1, 2). In Hong Kong, China, where the study was conducted, the HIV prevalence and incidence among GBMSM was 6.54% and 1.0 per 100 person-year in 2017, respectively (3, 4). Out of the 681 new HIV cases in 2017, 63% acquired it via homosexual or bisexual contact (3).
In line with numerous published studies, psychoactive substances were defined as the following: 1) ketamine, 2) methamphetamine, 3) cocaine, 4) cannabis, 5) ecstasy, 6) Dormicum/Halcion/Erimin 5/non-prescription hypnotic drugs, 7) heroin, 8) cough suppressant (not for curing cough), 9) amyl nitrite (popper), 10) GHB/GBL (γ-hydroxybutyrate), 11) 5-methoxy-N, N-diisopropyltryptamine (Foxy), and 12) mephedrone (5-7). Sexualized drug use (SDU) refers to the use of any of the abovementioned psychoactive substances before/during sexual intercourse (8). Chemsex is considered as a subset of SDU, which is commonly defined as the use of some specific psychoactive substances (methamphetamine, mephedrone, γ-hydroxybutyrate (GHB/GBL), ketamine and cocaine) before/during sexual intercourse (5-7). These psychoactive substances were mainly used to facilitate, initiate, prolong, sustain and intensify sexual encounter (8, 9).
A high prevalence of SDU was reported among GBMSM in the United States (43%), Australia (54%), and Western Europe (18-54%) (5, 6, 10-13). The rates were slightly lower in Asia, ranged from 28% in mainland China, 18% in Thailand, 14% in Vietnam, to 7% in Malaysia (14). Worldwide, the prevalence of chemsex ranged from 3% to 35% among GBMSM (7, 13, 15). A recent study reported that 12% of GBMSM in Hong Kong had SDU in the past six months (excluding the use of amyl nitrite alone) (16). Psychoactive substances adversely affect users’ capacity to perceive and respond to risks during sexual encounters, leading to high-risk sexual practices (e.g., condomless anal intercourse (CAI), group sex, fisting, etc.) (17) and hence HIV and other sexually transmitted infections (STI) (7). However, there was a lack of effective behavioral interventions in reducing psychoactive substance use and sexual risk behaviors among GBMSM with experience of SDU/chemsex (18-21).
Pre-exposure prophylaxis (PrEP) is a potentially risk reduction measure for GBMSM with experience of SDU/chemsex, which refers to the initiation of Tenofovir Disoproxil Fumarate/Emtricitabine before and during periods of HIV exposure among HIV-negative individuals in order to prevent HIV acquisition (22). With good adherence, PrEP could significantly reduce the risk of HIV infection among various at-risk groups, including GBMSM (22) and drug users (23). The World Health Organization (WHO) strongly recommends PrEP to all population at substantial risk of HIV infection (24). Clinical trials did not identify any significant safety concerns with daily PrEP use among psychoactive substance users (23).
A systematic review suggested that prevalence of PrEP use among GBMSM varied from 2.5% in Australia, 2-5% in Western Europe, to 9-12% in the United States (25). PrEP use is less common among GBMSM in Hong Kong (3.6% in 2017) (3). Willingness to use PrEP among GBMSM also varied between 19.1% and 96.2%, with a pooled estimate of 57.8% (26). Meta-analyses suggested that accessibility of PrEP and social stigma contributed to willingness to use PrEP among GBMSM, and country-specific factors were likely to affect willingness (26). In Hong Kong, due to the high cost of obtaining formal prescription in private clinics (US$1,000/month) and limited coverage of the PrEP demonstration project (70 participants), majority of local GBMSM PrEP users obtained the medication from overseas clinics or through online purchase (3). Previous studies showed that about half of Hong Kong GBMSM in general were willing to use free PrEP (3, 27). GBMSM with experience of SDU might have higher interest to use PrEP. One study in Hong Kong found that GBMSM with recent or ongoing SDU showed higher awareness of PrEP (28). While another study in the United States reported that GBMSM using amyl nitrite had higher prevalence of PrEP use (29).
In order to develop effective intervention to promote PrEP, it is important to understand factors associated with willingness to use PrEP among GBMSM with experience of SDU. At least three quantitative studies investigated factors associated with willingness to use PrEP among high-risk drug users (30-32). These studies had found a number of factors to be associated with willingness to use PrEP, including age, types and frequency of drug use, perceptions of HIV risk and PrEP (e.g., perceived effectiveness, would be less worried if on PrEP, concerns related to side effects, and confident to use/adhere to PrEP) (30-32). However, these studies mainly targeted heterosexuals and injective drug users. The findings may not be generalized to GBMSM with experience of SDU. Only one qualitative (33) investigated reasons for PrEP use among substance-using GBMSM. The results suggested that being able to relax and not having to worry about getting HIV, and increased comfort and openness to have sexual relationship with HIV positive partners were facilitators of PrEP use among substance-using GBMSM. The participants of the qualitative study also expressed concerns that substance use/SDU would disrupt their daily routine and negatively affect their ability to take PrEP or adhere to daily PrEP (33). These factors were considered by this study.
Theory-based interventions are more effective than non-theory-based ones (34). In this study, we applied the Theory of Planned Behavior (TPB) (35) as the theoretical framework. The TPB postulates that behavioral intention to adopt a health-related behavior (e.g., use PrEP) is a strong predictor of actual behavior. In order to form such an intention, one would evaluate the pros and cons of the behavior (positive and negative attitudes), consider whether their significant others would support such behavior (perceived subjective norm), and appraise how much control one has over the behavior (perceived behavioral control). In recent published studies, the TPB has been successfully used to explain willingness to use PrEP among GBMSM in general (27), transgender women sex workers (36) and heterosexual population (37). Moreover, many published studies also used the TPB to explain sexual behaviors (38-40), and utilization of HIV testing (41) and antiretroviral therapy (42).
In addition, mental health may be particular salient for PrEP use. Prevalence of mental health problems (e.g., depression, anxiety, and stress) are much higher among GBMSM than that of heterosexual men (43, 44). Although acceptance of same-sex relationships is growing in many western countries, stigma toward homosexuals are still widespread in China (45). As a result, previous studies reported high prevalence of mental health problems among GBMSM in China (46, 47). Moreover, psychoactive substance use and SDU were associated with poorer mental health status among GBMSM (48-51). Poor mental health status was found to be a barrier to start and adhere to PrEP (36, 52, 53). For instance, anxiety symptoms were associated with lower willingness to use PrEP among transgender women sex workers in China (36). Therefore, in this study, we investigated the associations between depressive/anxiety symptoms and willingness to use PrEP among GBMSM with experience of SDU in the past year.
To the best of our knowledge, there have been no study investigating willingness to use PrEP and associated factors among GBMSM with experience of SDU. Their prevalence of uptake and willingness to use PrEP as well as associated factors may be different from GBMSM without experience of SDU. To address these gaps, this study investigated PrEP uptake and willingness to use daily PrEP among GBMSM in Hong Kong with experience of SDU in the past year. Potential associated factors were also investigated, including variables related to socio-demographics, service utilization, sexual behaviors, patterns of SDU, perceptions related to PrEP based on the TPB, and mental health status.