INJECTION DRUG USERS (IDUs) are at risk for HIV seroconversion through risky sexual behavior, as well as through contaminated injection paraphernalia.1,2 Sexual risks, including multiple sexual partnerships, sex work, and unprotected intercourse, are common among IDUs.3–8 Although the predictors of sexual partnership patterns among IDUs have not received much research attention, both mathematical modeling and empiric research have demonstrated that multiple simultaneous partnerships can lead to high sexually transmitted infection rates.9,10 Furthermore, injection drug use has been related to engagement in heterosexual anal intercourse,11–13, a behavior that has been associated with greater risk for HIV transmission than vaginal sex in mathematical models.14 Reducing IDUs’ sexual risk is clearly an important step for stemming the HIV epidemic. However, HIV prevention interventions have had negligible effects on IDUs’ sexual risk,15–18 especially regarding unprotected intercourse with steady partners.19,20 Moreover, despite widespread public health prevention messages, a longitudinal study of IDUs in New York City reported only minor reductions in sexual risk across a 4-year period.21
Establishing the factors that predict sexual risk among IDUs could aid in the development of interventions that focus on changing IDUs’ sexual behavior. To date, only a few predictors of IDUs’ sexual risk have been identified, including HIV serostatus, partner type, gender, intoxication, and drug preference. IDUs who are HIV-positive are more likely to use condoms than are those with negative serostatus.3,21–23 In addition, IDUs are less likely to use condoms with steady partners than with casual or paying partners,23–25 although gender may moderate this effect. Whereas some research indicates that female IDUs are less likely to use condoms with steady partners than with paying partners,26,27 other research has found that male IDUs exhibit similarly low levels of condom use for both types of partners.4 Nevertheless, this research has not fully examined the patterns of sexual partnerships among IDUs, especially the circumstances that lead IDUs with steady partners to engage in other sexual relationships, either concurrently or serially. If IDUs do not use condoms with their steady partners, but engage in intercourse with multiple individuals, either simultaneously or within a short timeframe, they may be putting their steady partners at risk. In particular, STD risk is heightened when the duration of time between serially monogamous partners decreases or the prevalence of concurrent partnerships increases.28,29 Furthermore, individuals who are monogamous themselves may have partners in concurrent sexual networks. Thus, even if IDUs engage in serial monogamy, they may be putting themselves and their partners at considerable risk if they engage in unprotected intercourse and the length of time between new partners is short.
IDUs’ sexual behavior is intimately tied to their substance use. Both injecting and noninjecting drug users who report being “high” when having sex are less likely to use condoms,24 and some drugs may have more of an influence on sexual risk than others. Amphetamine use, in particular, has been linked to risky sexual practices, including unprotected sex and increased numbers of partners.30 In a qualitative study of injection drug-using men who have sex with men (MSM),4 over one third indicated that they used amphetamines to enhance sex. Similarly, injecting cocaine or (smoking or injecting) crack has been related to higher levels of sexual risk.5,31–33 In contrast, heroin injection has been associated with lower sexual risk.5,33 Illicit substance use has also been related to increased heterosexual anal sex, although almost none of this research has specifically examined IDUs or use of different types of drugs.34–36 In addition, alcohol use has been associated with sexual risk among IDUs.37,38 However, little is known about the impact of alcohol on condom use beyond the effects of other types of substances.
For a comprehensive understanding of HIV risk among male and female IDUs, sexual risk must be examined in the context of injection risk. Syringe-sharing has been associated with lower condom use and greater numbers of sexual partners.5,32 Somlai and colleagues5 found that sharing syringes with sexual partners was associated with a greater number of unprotected anal sex episodes, as well as a greater number of sexual partners overall. In addition, women tend to be more likely than men to have sexual partners with whom they also inject, and this can lead to greater sexual risk.39,40 For instance, research conducted in San Francisco demonstrated that young female IDUs were more likely than young male IDUs to engage in injection risk behaviors, and overlapping sexual and injection partnerships largely accounted for this gender difference.39 However, more research is needed on overlapping injection and sexual risks among IDUs and gender differences in these behaviors.
The purpose of the present analysis was to examine the levels and predictors of sexual risk among a large sample of male and female IDUs recruited from syringe exchange programs (SEPs) in California. The data gathered from our study of IDUs in SEPs allowed us to examine 3 different types of sexual risk behavior that would help to identify characteristics of IDUs who are most in need of prevention services: unprotected anal/vaginal intercourse, multiple recent sexual partnerships that included a steady partner, and anal intercourse between male and female IDUs. We examined the relationships of these risky behaviors to sociodemographic characteristics, STD history, HIV status, sexual and injection risk behaviors and partnerships, and use of different types of injection and noninjection substances. Because sexual and injection risks can be different for male and female IDUs, we stratified all analyses by gender.
This analysis stems from data collected as part of a study addressing the impact of California law Assembly Bill 136 (AB136) on SEPs and their clients. AB136 was enacted in January 2000 and grants local cities and counties in California the authority to legalize SEPs pursuant to a declaration of a local public health emergency. Twenty-four SEPs agreed to participate in our study, representing 96% of the SEPs in California at the beginning of 2000. The SEPs operated in rural and urban areas in 16 California counties and all major cities in the state. Three annual cross-sectional samples of between 7 and 25 SEP clients were recruited from 24 SEPs from 2000–2003 (N = 1584). SEP clients were eligible for a risk-behavior interview and HIV testing and counseling if they reported drug injection and syringe exchange use in past 30 days. A total of 139 participants were eliminated from the dataset before analysis either because 1) their age, last 4 digits of their social security number, race, ethnicity, years of education, and city of residence duplicated those of a prior respondent; and/or 2) they responded affirmatively to the question “Have you previously participated in this research study?” This resulted in a final sample of 1445 respondents.
After determination of eligibility and provision of informed consent, participants were interviewed by a trained research interviewer/counselor in a private space. Private spaces, which varied by field location, included rooms in SEP offices, cars, park benches, temporary tents, sidewalks, and participants’ homes for delivery clients. Participants’ responses were entered into a software program by study interviewers on laptop computers (computer assisted personal interview; NOVA Research, Bethesda, MD). Participants also received HIV counseling and testing. They were paid $10 for the interview and asked to return for HIV test results disclosure and counseling 1 to 2 weeks later. Study methods were approved by the Committee on Human Research at RAND, University of California, San Francisco, and University of California, Davis.
The assessment included items on HIV risk behavior (ie, injection and sexual risk practices), HIV/AIDS/hepatitis C virus knowledge, medical history, incarceration history, and utilization of SEPs and other social or medical services. The variables used for the present analysis are described subsequently.
Standard questions were used to assess sociodemographic characteristics, including age, gender, race/ethnicity, years of education, income from all sources and employment in the last 6 months, homeless status, urban/rural residence, and sexual orientation. Income was dichotomized into <$1000 per month and ≥$1000 per month.
Specimens were analyzed for HIV antibodies using enzyme immunoassay (EIA). EIA-positive specimens were confirmed using Western blot assay (Wb). As described by the Centers for Disease Control and Prevention, criteria for a seropositive Wb result were the presence of reactive bands at 2 of the following locations: p24, gp41, and gp120/160.
Sexually Transmitted Disease History.
Participants were asked if they had been diagnosed with any STD in the past 5 years.
For each of 5 drugs (ie, speedball [heroin and cocaine mixed], heroin, powder cocaine, crack cocaine, amphetamines), respondents reported whether they had injected the drug and/or used the drug without injecting in the last 30 days. Response options were “yes” and “no.”
Respondents reported the number of days in the last month that they drank any alcoholic beverage. Alcohol use was dichotomized into “any alcohol” versus “no alcohol” intake in the past month.
Injection Risk Behaviors.
To determine receptive syringe-sharing practices, participants were asked “In the last 30 days, how many times did you inject using syringes/needles that you know had been used by someone else (including a close friend or lover)?” To determine distributive syringe-sharing practices, participants were asked “In the last 30 days, how many times did you give or loan syringes/needles that you had used to someone else (including a close friend or lover) who then used them?” Response options for both questions were “yes” and “no.” Because these 2 variables were highly correlated (r = 0.55, P <0.001), we combined them into 1 injection risk variable indicating if the respondent had either shared or loaned used needles in the past 6 months (yes/no).
Participants were asked the number of male and female sexual partners that they had, whether they had a steady sexual partner (yes/no) and whether they had been paid money or drugs for sex in the last 6 months (yes/no). For a measure of recent multiple sexual partnerships, the number of male and female partners reported was combined and recoded as “1” or “more than 1” sexual partner in the last 6 months. These 2 variables were combined and recoded into respondents who reported both a steady partner and multiple partners versus all other respondents (ie, respondents without a steady partner or multiple partners, or respondents with either a steady partner or multiple partners). The former group (ie, recent multiple partnerships including a steady partner) was of most interest to the present analysis.
Sexual Behavior and Condom Use.
Participants who reported having male and/or female partners were asked whether they had vaginal, oral, or anal sex with their male and/or female partners. In addition, men who reported having male partners were asked if they had receptive or insertive anal sex. To assess condom use, participants reporting vaginal, anal, and/or oral sex were asked the percentage of time that they used latex condoms for these activities in the past 6 months. Responses were dichotomized into 0% to 99% condom use (“never/sometimes”) or 100% (consistent) condom use (“always”). For analysis purposes, reports of consistent condom use for vaginal and anal sex were combined into 1 overall measure of 100% condom use for vaginal and/or anal sex in the past 6 months. Participants who were not sexually active in the past 6 months were not included in calculations of any of the sexual behavior or condom use variables.
Descriptive statistics (eg, means, frequencies, variability) were examined for all study variables. Logistic regression was used to examine the unadjusted associations of sociodemographic factors, sexual and injection risk variables, and substance use variables with 3 types of sexual risk behaviors in the past 6 months: heterosexual anal intercourse, multiple recent partnerships that included a steady partner, and unprotected intercourse, by gender. Multivariate logistic regressions were then used to predict each type of sexual risk for men and women separately, only including those variables that had significant (P <0.05) unadjusted relations with the sexual risk variable of interest.
Participants ranged in age from 18 to 77 (mean = 42 ± 11). The majority was male (68%), and men (mean = 43.3, standard deviation [SD] = 10.5) were approximately 4 years older than women (mean = 39.3, SD = 10.8) on average (t  = 4.06, P <0.001). Over half (53%) were white, 19% black, and 20% Latino. In terms of socioeconomic status, two thirds had completed high school or greater, 44% were employed in the last 6 months, and 39% had incomes of $1000 or more per month. Nearly 50% were homeless, and most (62%) lived in an urban setting. Same-sex partnerships were reported by 7% of men and 15% women.
HIV Status, Sexual Risk, and Injection Risk
Four percent (n = 62) tested positive for HIV antibodies, and 7% reported having any STD in the last 5 years; women (11%) were more likely than men (5%) to report having had a 5-year history of STD (chi-squared  = 14.3, P <0.001). The majority of men (68%) had a female sexual partner, and the majority of women (76%) had a male sexual partner in the past 6 months. Of the three fourths who were sexually active (n = 1098) in the last 6 months, almost half (47%) had more than 1 sexual partner, the majority (71%) had a steady sexual partner, and 14% had been paid with money or drugs for sex in the past 6 months. Over one fourth (26%) reported having multiple recent sexual partnerships that included a steady partner. Women were more likely than men to engage in sex work (26% vs. 8%; chi-squared  = 74.2, P <0.001), have a steady sexual partner (81% vs. 66%, chi-squared  = 27.8, P <0.001), and have multiple recent sexual partnerships that included a steady partner (34% vs. 22%; chi-squared  = 18.8, P <0.05). In terms of injection risk, 41% engaged in either receptive or distributive injection syringe-sharing.
Table 1shows frequencies of the different types of sexual behaviors and consistent condom use in the sexually active sample. The majority of women did not use condoms consistently, with 80% reporting any unprotected vaginal sex, three fourths reporting any unprotected anal sex, and 90% reporting any unprotected oral sex. Likewise, only approximately one fifth of sexually active men who had sex with women used condoms consistently for vaginal or anal sex, and only 5% used condoms for oral sex with female partners. Although most MSM (85%) did not use condoms consistently for oral sex, substantial proportions used condoms for receptive (37%) and insertive (28%) anal sex.
Heroin (78%) was the most frequently injected drug in the last 30 days, followed by amphetamines (36%), speedball (34%), and powder cocaine (21%). Although crack cocaine was the least frequently injected drug (7%), it was the most frequently used noninjected drug (29%). In addition, one fifth of participants used amphetamines, one tenth used heroin, 7% used powder cocaine, and 4% used speedball without injecting. MSM were less likely than heterosexual men to inject heroin (53% vs. 80%, respectively; chi-squared  = 21.5, P <0.001) and more likely to use amphetamines (either by injecting, 68% vs. 34%, respectively; chi-squared  = 36.7, P <0.001, or noninjecting, 44% vs. 18%, respectively, chi-squared  = 29.1, P <0.001) and to use cocaine without injecting (16% vs. 7%, respectively; chi-squared  = 8.6, P <0.01).
Predictors of Condom Use
Table 2shows the unadjusted and adjusted associations of condom use with sociodemographics, sexual/relational risk, injection risk, and different types of injection and noninjection drug use by gender. In multivariate analyses, being HIV-positive, having multiple partners, not having a steady partner, and not sharing syringes or injecting amphetamines were significant. Specifically, men who were HIV-positive and men with multiple partners showed higher odds of consistent condom use than men who were HIV-negative and men with only 1 partner, respectively. On the other hand, men who had a steady sexual partner, men who shared used syringes, and men who injected amphetamines each had lower odds of consistent condom use, as compared with men who did not have a steady sexual partner, who did not engage in injection risk practices, and who did not inject amphetamines, respectively.
For women, multivariate models indicated that women who had been paid for sex in the past 6 months had higher odds of always using condoms than women who had not been paid for sex; women who shared used syringes with other IDUs and women who had a steady sexual partner each showed lower odds of using condoms consistently than women who did not share syringes and women who did not have a steady partner, respectively.
Predictors of Heterosexual Anal Intercourse
Table 3presents the unadjusted and adjusted associations for anal sex between men and women. In multivariate analyses of the male subsample, having had an STD, having multiple sexual partners, using amphetamines, and engaging in injection risk practices each independently predicted having anal sex with women in the past 6 months. For women, only younger age and amphetamine use significantly predicted anal intercourse in the multivariate analysis.
Predictors of Recent Multiple Partnerships Including a Steady Partner
Adjusted odds ratios for having both a steady and multiple sex partners are shown in Table 4. In multivariate models of men, only engagement in sex work, speedball injection, and noninjection use of amphetamines increased the odds of having both a steady partner and multiple partners among male participants. In multivariate models of the female subsample, younger age, having a history of STD, engagement in sex work, and alcohol use remained significant correlates of having both a steady and multiple sexual partners.
We found high levels of sexual risk behavior in this large sample of IDUs recruited from SEPs across the state of California. In accordance with previous work that examined other samples of IDUs,4,5,26 a sizable majority of the sample was sexually active, had multiple sexual partners, and did not use condoms consistently for anal, vaginal, or oral sex. Women in particular were likely to engage in sex work, and both women and men reported substantial levels of anal intercourse. Risky sexual behaviors tended to co-occur with high levels of syringe-sharing behaviors, demonstrating a need for SEPs to better incorporate safer sexual behavior counseling into their programs. (Nearly all of the SEPs surveyed distributed condoms in addition to syringes, although numbers of condoms and syringes distributed varied substantially.)
Our finding that a substantial proportion (approximately one fifth) of the sample engaged in heterosexual anal intercourse mirrored those of other heterosexual samples.13,34,35 Our results also indicated that anal sex between men and women was connected to a generally risky lifestyle that included a history of STDs, multiple sexual partnerships, syringe-sharing, and amphetamine use. Thus, anal sex may represent one facet of a constellation of risky behaviors that ultimately leads to HIV infection among heterosexuals. Comprehensive prevention interventions are therefore called for, which address multiple sexual and injection risk behaviors. Most importantly, because HIV transmission may be more likely from anal sex than vaginal sex, even when condoms are used,41 our data speak to a need to openly and explicitly address heterosexual anal sex within prevention intervention frameworks.
Women who engaged in sex work and men who reported multiple partners tended to use condoms for every sexual act, whereas both men and women who reported having steady partners were less likely to use condoms consistently. These results are consistent with our own and others’ research findings that IDUs are unwilling to use condoms with steady partners because they associate condom use with a lack of intimacy and because they believe long-term partners are not at risk.27,42 Similarly, research has shown that female sex workers are reluctant to use condoms with steady partners, as opposed to sex work-related partners, because they associate condom use with paying clients.43 Thus, interventions are needed that work with couples to destigmatize condom use and provide credible information about the pros and cons of eliminating condom use from their relationship. For example, intervention facilitators could address negative attitudes about condom use and misconceptions about sexual risk from steady partners, as well as offer information about contraceptive alternatives to condoms. Although some intervention work has targeted individuals’ condom use with main partners,44 sexual risk interventions that specifically focus on IDUs in steady partnerships have not been developed.
Our findings regarding IDUs who reported multiple sexual partnerships that included steady partners also provide an indication of selective sexual risk-taking practices such that IDUs with riskier partnerships were more likely to use condoms. These results parallel findings on selective syringe-sharing among IDUs, which demonstrate that IDUs may attempt to limit their syringe-sharing to those in their close personal networks.45 Selective risk-taking strategies can work if both partners have been tested for HIV and remain monogamous, and if their injection networks are free of infection and closed to outside individuals. Nevertheless, to the extent that steady partners engage in risky injection and sexual behaviors outside of their partnerships or closed networks, selective sexual risk-taking may be ineffective for risk reduction. In the present sample, over one fourth of men and women engaged in relations with individuals other than their current steady partner in the past 6 months, and both sex work and substance use were associated with these risky patterns of sexual partnerships. Perhaps of most concern is that female IDUs with a history of STDs were twice as likely to have both a steady partner and multiple partners. Given that the presence of some STDs may facilitate HIV transmission,46 these types of risky partnerships may be a significant contributor to the spread of HIV.
HIV-positive serostatus and amphetamine injection were key predictors of men’s condom use behavior, and amphetamine use was related to engaging in heterosexual anal intercourse among both male and female IDUs. In addition, men who used amphetamines were more likely to have both a steady partner and multiple partners in the past 6 months. The association between HIV serostatus and condom use has been frequently observed,21–23,47 as has the link between amphetamine use and risky sexual behavior.48–52 However, amphetamine use has been predominantly studied among MSMs who may use amphetamines in the context of continuous sexual encounters with multiple partners.50 Similar to the proposed study, the small amount of research examining the effects of amphetamine use among IDUs has observed that amphetamine use is related to greater sexual risk behavior, especially among male IDUs.30 The close connection between amphetamine use and sexual risk points to a need to integrate HIV risk reduction counseling with substance abuse and syringe exchange programs. However, to design effective interventions, additional research is needed examining the environment in which amphetamine use occurs among IDUs, as well as IDUs’ motivations for choosing to use amphetamines versus other types of substances.
Any conclusions based on the current study’s results must be considered in light of several limitations. Because the study design was cross-sectional, the direction of the relations presented here is unknown. In addition, variables may moderate or mediate some of the obtained associations. For instance, amphetamine use could lead to higher levels of sexual risk, or individuals who are higher in sensation-seeking may be more likely both to practice unsafe sex and to use amphetamines. Moreover, all participants were clients of SEPs in California, and results may not extend to other IDUs or clients of SEPs in other states. Nevertheless, because SEPs are able to reach large numbers of IDUs, SEPs can be ideal settings in which to conduct sexual risk reduction outreach activities that address sexual risk within the context of injection behavior.
Another limitation of our study relates to our measure of sexual partnerships. We classified individuals who reported having both a steady partner and multiple partners in the past 6 months as riskier than those who reported no partners, only a steady partner, or multiple partnerships that did not include a steady partner. However, individuals in this “risky” category may represent several different partnership patterns that confer different degrees of risk: serial monogamy and serial or concurrent partnerships including both steady and casual partners. Because we did not measure the timing and overlapping nature of recent sexual partnerships, or the configuration of sexual networks,53 we were unable to distinguish these different types of partnership patterns or to provide a sophisticated analysis of the interaction of multiple risks within IDUs’ networks. However, although serial monogamy is considered to be less risky than the other 2 categories, all 3 can lead to substantial risk, especially because IDUs with steady partners were less likely to report condom use. Moreover, partnership patterns were measured within a relatively short timeframe (6 months), and STD infection is more likely when the length of time between partners is short.27,28 Thus, although our measure of sexual partnerships is not informative for calculating precise risk estimates, IDUs who were categorized as having multiple partnerships including a steady partner were most likely at higher risk than those who were not.
Although the rate of HIV risk behaviors was high in the present sample, the prevalence of HIV and prior STD reports were low. These results mirror those of others, who have found high levels of overlapping risk behaviors (eg, unprotected anal and vaginal sex, syringe-sharing, concurrent partnerships) but low levels of HIV transmission, especially within IDUs’ sexual networks.54 Thus, although risk behaviors are a necessary predictor of HIV transmission, they are not sufficient; HIV also needs to be present within the sexual and injection partnership network and communities of those who are practicing risky behaviors. Because HIV has not yet reached high incidence levels among IDUs in the western United States, risk behaviors in this population are not necessarily leading to new infections. Nevertheless, as a result of the high levels of risk behavior observed, as well as the presence of multiple partnerships, the potential for rapid spread of HIV in IDU networks is considerable if the prevalence of HIV grows among IDUs. Prevention for IDUs, especially regarding condom use in steady partnerships, remains a necessary component of interventions to thwart future infections.
In summary, the current study provides information about the factors that may lead to increased sexual risk behavior among IDUs participating in SEPs. Despite participation in SEP programs, the majority of IDUs continued to engage in multiple behaviors that placed them at risk for HIV and other STDs. Prospective studies on predictors of sexual risk among IDUs would be invaluable in identifying factors that may be amenable to intervention. The research presented here suggests that interventions focused on increasing the use of condoms within steady partnerships may be most successful in reducing sexual risk among IDUs.
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