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American Journal of Public Health logoLink to American Journal of Public Health
. 2015 Sep;105(9):1866–1871. doi: 10.2105/AJPH.2014.302366

Buffering Syndemic Effects in a Sexual Risk-Reduction Intervention for Male Clients of Female Sex Workers: Results From a Randomized Controlled Trial

Eileen V Pitpitan 1,✉, Steffanie A Strathdee 1, Shirley J Semple 1, Claudia V Chavarin 1, Carlos Magis-Rodriguez 1, Thomas L Patterson 1
PMCID: PMC4529804  NIHMSID: NIHMS685586  PMID: 25713953

Abstract

Objectives. We sought to test the efficacy of a sexual risk intervention for male clients of female sex workers (FSWs) and examine whether efficacy was moderated by syndemic risk.

Methods. From 2010 to 2014, we conducted a 2-arm randomized controlled trial (60-minute, theory-based, safer sex intervention versus a didactic time-equivalent attention control) that included 400 male clients of FSWs on the US–Mexico border with follow-up at 4, 8, and 12 months. We measured 5 syndemic risk factors, including substance use and depression. Primary outcomes were sexually transmitted infections incidence and total unprotected sex with FSWs.

Results. Although participants in both groups became safer, there was no significant difference in behavior change between groups. However, baseline syndemic risk moderated intervention efficacy. At baseline, there was a positive association between syndemic risk and unprotected sex. Then at 12 months, longitudinal analyses showed the association depended on intervention participation (B = −0.71; 95% confidence interval [CI] = –1.22, –0.20; P = .007). Among control participants there still existed this modest association (B = 0.36; 95% CI = –0.49, 1.22; P = .09); among intervention participants there was a significant negative association (B = −0.35; 95% CI = –0.63, –0.06; P = .02).

Conclusion. A brief intervention might attenuate syndemic risks among clients of FSWs. Other populations experiencing syndemic problems may also benefit from such programs.

Male clients of female sex workers (FSWs) represent a “bridge population” that has the potential to transmit HIV and sexually transmitted infections (STIs) between higher-risk groups (FSWs) and lower-risk groups (e.g., their wives).1–3 Globally, male clients of FSWs exhibit high-risk sexual behaviors,4–8 as well as higher STI incidence compared with other men.9 Unfortunately, little intervention work has targeted male clients.

In 2007, Lowndes et al. implemented a behavioral intervention focusing on condom promotion among male clients of FSWs in Cotonou, Benin.10 Results suggested that male clients of FSWs in a resource-constrained country can reduce their sexual risk behavior through participation in a targeted behavioral intervention. However, this study lacked randomization and a control condition, precluding the ability to evaluate efficacy to reduce sexual risk behavior. A recent review of randomized trials and quasi-randomized trials of behavioral HIV prevention interventions among sex workers and clients did not identify a single randomized controlled trial targeted for male clients.11

In Tijuana, Mexico, a border city along San Diego, California, there are an estimated 6000 to 10 000 FSWs offering sexual services to men from both countries.12 Tijuana has an HIV prevalence that is double the national average, and HIV is highest among high-risk groups including FSWs (approximately 6%).12–14

In 2008, we conducted pilot research with 400 male clients of FSWs in Tijuana.13 HIV prevalence among clients was similar to that of FSWs (approximately 5%). Clients reported sex with an FSW an average of 26 times in the past year, once every 2 weeks in the past 4 months, and half reported recent unprotected sex with FSWs. Data were used to develop the first sexual risk-reduction intervention for male clients of FSWs. Herein, we aim to first evaluate the efficacy of our brief intervention, using the rigor of a randomized controlled trial. Whereas evaluating an intervention’s efficacy is a necessary step for HIV prevention, scientists must also examine for whom or under what conditions an intervention is efficacious (i.e., test moderators) to best inform prevention strategies both practically and theoretically.

In addition to demonstrating risky sexual behavior, our pilot research with male clients in Tijuana showed that history of drug use was prevalent (88% reporting lifetime drug use) and was associated with unprotected sex with FSWs. These data also showed that the clients were more likely to engage in risky sex if they consumed alcohol at hazardous levels.15 Finally, our qualitative data suggested that vulnerability to HIV was associated with mental health problems like depression or loneliness.16,17 These findings are consistent with previous research on syndemic theory.

Research has demonstrated the multiple co-occurrence of psychosocial problems (e.g., substance use, violence) and their additive effect on HIV risk behavior, called “syndemics.”18–21 While the specific factors that are included in the operationalization of a syndemic differ and depend on the specific population and region,21,22 studies have essentially found a dose–response relationship such that individuals who report more psychosocial problems are more likely to engage in higher sexual risk behavior or are more likely to be infected with HIV.23 The second aim of the current research was to examine syndemics as a potential moderator of intervention efficacy. In light of the important role that syndemics play in HIV across high-risk populations, and based on our pilot data, we hypothesized that men who experienced more syndemic problems at baseline would be more likely to benefit from the intervention than men who experienced fewer syndemic problems. Although our sexual risk-reduction intervention was not designed to directly address syndemic problems, it was based on cognitive behavioral therapy, social cognitive theory, and the theory of reasoned action, and we included in the intervention theoretical elements and motivational interviewing techniques designed to promote safer sex behavior by addressing perceived barriers to safer sex.

METHODS

Detailed methods, sample characteristics, randomization assurance, and study flow (CONSORT diagram) are published elsewhere.24 Study methods are summarized as follows.

Ethics Statement

We obtained written informed consent. Institutional reviews boards in the United States and Mexico approved the study protocol.

Participants

We recruited participants between September 2010 and October 2012. By design, half of the participants were from San Diego, half from Tijuana. We included HIV-negative, biological males who were at least 18 years old; living in either city; reported purchasing sex for money, drugs, shelter or goods; and reported having unprotected sex with an FSW in Tijuana in the last 4 months.

Recruitment

We used time–location sampling within each colonia (neighborhood) in Tijuana to recruit male clients.25

Procedures

We administered measures using computer-assisted personal interviewing. After completing the approximately 45-minute baseline assessment, participants were randomly assigned to either the 60-minute, single session, Hombre Seguro intervention group or a time-equivalent attention control condition. Participants later returned to complete follow-up assessments at 4, 8, and 12 months.

Intervention and Control Conditions

Details of both the control and intervention conditions have been described elsewhere24 and they are summarized as follows.

Didactic control condition.

Participants in the control condition received a modified version of the Centers for Disease Control and Prevention revised guidelines for HIV counseling, testing, and referral26 and materials from Mexico’s National Center for AIDS Studies.27 The counselor guided the participant through a personal risk assessment, then the counselor and participant discussed specific risky incidents and barriers to change. Counseling topics focused on HIV/AIDS knowledge and development of a personalized risk-reduction plan. In this condition, there were no theory-driven, active skill-building elements, or exercises oriented toward safer sex practices.

Hombre Seguro intervention.

The active safer sex intervention incorporated principles of motivational interviewing, cognitive behavioral therapy, social cognitive theory, and the theory of reasoned action.28–30 The session first focused on using motivational interviewing techniques to enhance the participant’s perceived need and desire to change high-risk sexual behaviors. For example the counselor used a decisional balance exercise to help the client understand motivations that underlie his sexual behavior with FSWs, eliciting from clients self-motivated reasons for change and enhancing self-efficacy for change. Another goal of the session was to help the client develop insights into personal triggers of unsafe sex with FSWs, including but not limited to negative attitudes toward condoms, substance use, and negative thoughts and emotions. This was based on cognitive behavioral therapy, social cognitive theory, and the theory of reasoned action to explore the participant’s personal cognitive, emotional, and behavioral triggers to unsafe sex and barriers to safe sex. From there, the counselor and client worked together to problem-solve barriers to safer sex and to identify and practice social cognitive and behavioral strategies to increase knowledge, self-efficacy, and positive outcome expectancies in relation to condom use. These strategies included reframing negative thoughts and emotions and enhancing communication and assertiveness skills. Among the exercises, role-playing between the counselor and client helped build and strengthen safer sex skills. Overall, participants involved in Hombre Seguro were highly engaged in the counseling session.

Measures

STI incidence outcome.

At all visits, clients were biologically screened for syphilis, chlamydia, and gonorrhea. STIs detected within 12 months after baseline were coded for outcomes.

Sexual risk behavior outcome.

In open-ended items, participants were asked to report each of the following with an FSW in the past 4 months: number of vaginal sex acts, times used a condom during vaginal sex, anal sex acts, and times used a condom during anal sex. We computed total number of unprotected vaginal and anal sex acts with an FSW in the past 4 months as an outcome.

Syndemic Factors

Drug use.

We asked participants how often they used the following drugs in the past 4 months in separate items: marijuana, heroin, inhalants, methamphetamine, ecstasy, cocaine, heroin and cocaine mixed together (aka “speedball”), heroin and meth mixed together (aka “Mexican speedball”), tranquilzers, barbiturates, amyl nitrate, gamma-hydroxybutyrate, Ketamine, or “any other drug.” We gave participants who reported using any drug at least once a week in the past 4 months a score of 1 for “yes”; all others were given a zero for “no.”

Alcohol use.

We asked participants to complete the 10-item Alcohol Use Disorders Identification Test.31 Individuals who received a total score of at least 8 are considered “hazardous drinkers.”32 We created a dichotomous variable “hazardous alcohol use” (1 = yes, 0 = no).

Depression.

We assessed depressive symptoms by using the short version 10-item Center for Epidemiological Studies–Depression scale (α = 0.77).33 For the dichotomous variable “depressive symptoms,” participants who scored 11 or above were given a score of 1 for “yes,” and those who scored 10 or below were given a score of zero for “no.”

Lifetime history of abuse.

We asked participants whether they have ever experienced emotional, physical, or sexual abuse in 3 items. For the dichotomous variable “lifetime abuse,” participants who reported ever experiencing any abuse were given a score of 1 for “yes”; those who never experienced abuse were scored zero for “no.”

Recent incarceration.

Participants were asked whether they spent any time in jail or prison in the past 4 months. We created a dichotomous variable recent incarceration with 1 for “yes,” and zero for “no.”

We then divided participants into 6 groups based on whether they experienced 0 to 5 of the risk factors.

Analysis Plan

For the STI outcome, we conducted Generalized Estimating Equations (GEE) with a binomial probability distribution and logit link function, with intervention group predicting testing positive for any STI at any time during the course of follow-up. In this analysis, a total of 374 participants were included (n = 26 did not complete STI testing at all of the follow-up visits). For sexual risk behavior, we conducted regression via GEE with intervention group, time, and the 2-way interaction entered as predictors of total unprotected sex acts with an FSW in the past 4 months. All 400 participants were analyzed for this outcome. To examine baseline level of syndemic risk as a moderator, we used GEE and entered intervention group, time, syndemic risk factor score (centered around the sample mean), and all possible 2- and 3-way interactions as predictors of sexual risk behavior. In GEE, sexual risk behavior was specified along a Poisson probability distribution and log-link function.

RESULTS

Mean age of our sample was 37.8 years (SD = 10.7) and mean number of years of education was 9.2 years (SD = 3.4). A total of 349 men (87.7%) identified as Hispanic (versus non-Hispanic). In addition, 81 men (20.4%) were US-born, 196 (49.2%) lived in the United States (versus Mexico), 136 (34.2%) had been deported from the United States, 125 (31.4%) were married or in a common law marriage, and 249 (62.6%) were employed. In terms of the 5 syndemic factors we assessed at baseline, we found that 320 male clients (80.4%) reported recent and frequent drug use, 195 (49.0%) reported hazardous alcohol use, 141 (35.4%) screened positive for depressive symptoms, 134 (33.7%) reported ever experiencing abuse, and 76 (19.1%) reported recent incarceration.

Intervention outcomes

STI incidence.

There was a nonsignificant effect of the intervention on getting any STI during follow-up (Wald χ2 = 1.44; B = −0.32; 95% confidence interval [CI] =  −0.83, 0.20; P = .23). This yields a small effect size of the intervention (Cohen's d =  0.12). Overall, 16.0% (n = 32) of participants in the Hombre Seguro intervention group acquired an STI over the course of follow-up, compared with 20.0% (n = 40) in the control group, representing 20% fewer incident STIs in Hombre Seguro.

Unprotected vaginal and anal sex with FSWs.

GEE revealed a nonsignificant interaction effect between intervention group and time (B = −0.02; 95% CI = −0.38, 0.35; P = .93) on sexual risk behavior. Intervention groups did not differ from one another at baseline in total unprotected sex acts with FSWs (B = 0.03; 95% CI = −0.40, 0.45; P = .9). There was a significant effect of time, with all participants demonstrating a decrease in sexual risk behavior over the course of the study year (B = −0.88; 95% CI = −1.13, −0.63; P < .001), with an average decline of 0.88 unprotected sex acts with FSWs across each follow-up.

Syndemic Risk as a Moderator of Intervention Efficacy

Prior to examining baseline syndemic risk as a moderator of intervention efficacy, we sought to examine baseline characteristics of and associations between the syndemic risk factors to replicate previous work on syndemics.

We found that 8% of men (n = 32) did not experience any of the risk factors, 22% (n = 89) experienced 1, 31% (n = 125) experienced 2, 24% (n = 97) experienced 3, 10% (n = 39) experienced 4, and 4% (n = 16) experienced all 5 risk factors. Table 1 shows intercorrelations between the risk factors. We found that out of 10 possible associations, 5 were statistically significant (P < .05) and 1 was marginally significant (P < .1). Figure 1 summarizes how total number of unprotected sex acts increased as number of risk factors increased at baseline. Results using GEE with a negative binomial and log link function showed that at baseline number of risk factors was significantly and positively associated with more unprotected sex acts with FSWs in the past 4 months (B = 0.20; 95% CI = 0.05, 0.35; P = .01), with an average increase of 0.20 unprotected sex acts with FSWs across number of syndemic problems. Importantly, the interaction between number of risk factors and intervention condition was not significantly associated with unprotected sex with FSWs at baseline (B = 0.14; 95% CI = −0.16, 0.44; P = .36).

TABLE 1—

Baseline Associations Among Syndemic Risk Factors Among Male Clients of Female Sex Workers: Tijuana, Mexico, 2010–2014.

Risk Factor Drug Use, B (95% CI) Alcohol Use, B (95% CI) Depression, B (95% CI) Lifetime Abuse, B (95% CI)
Alcohol Use 3.87*** (1.96, 7.66)
Depression 1.65 (0.86, 3.17) 1.42 (0.94, 2.14)
Lifetime Abuse 1.33 (0.70, 2.53) 1.27 (0.84, 1.94) 2.97*** (1.93, 4.59)
Recent Incarceration 3.48* (1.22, 9.99) 1.28 (0.77, 2.11) 1.99** (1.20, 3.30) 2.20** (1.32, 3.66)
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Note. CI = confidence interval.

*P < .05; **P < .01; ***P < .001.

FIGURE 1—

FIGURE 1—

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Total unprotected sex acts with female sex workers at baseline by number of baseline syndemic risk factors: Tijuana, Mexico, 2010–2014.

Intervention group and sexual risk behavior by syndemic risk factors.

We tested our second aim that after counseling, the effect of intervention group and unprotected sex with FSWs would depend on baseline syndemic risk (in other words, that the intervention is a buffer of syndemic risk). Results using GEE with a negative binomial and log-link function showed that at 12 months there was a significant 2-way interaction between intervention group and number of risk factors (B = −0.71; 95% CI = −1.22, −0.20; P = .007). Results (Figure 2) showed that among participants in the control group, number of risk factors was still associated, albeit modestly, with unprotected sex acts with FSWs (B = 0.36; 95% CI = −0.49, 1.22; P = .09). By contrast, the association was significant and negative among participants who received the intervention (B = −0.35; 95% CI = −0.63, −0.06; P = .02,); as number of syndemic risk factors increases, sexual risk behavior decreases for participants in Hombre Seguro, suggesting that the intervention buffered the effect between syndemic risk and sexual risk behavior found at baseline.

FIGURE 2—

FIGURE 2—

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Total number of unprotected vaginal and anal sex acts with female sex workers in the past 4 months (reported at 12 months follow-up), by baseline syndemic problems and Hombre Seguro intervention group: Tijuana, Mexico, 2010–2014.

Sexual risk behavior change over time.

We examined behavior over time using a GEE model with time, number of syndemic risk factors, and intervention condition entered in as predictors of unprotected sex with FSWs in the past 4 months. There was a significant 3-way interaction such that sexual behavior change over time depended on intervention group and number of risk factors. For illustration purposes (Figure 3), we separated participants into 2 groups: lower-risk participants who reported 0, 1, or 2 syndemic risk factors at baseline, and higher-risk participants who reported at least 3 of the 5 risk factors at baseline. Using this grouping variable, posthoc analyses using GEE showed that participants who were at higher-risk at baseline and did not receive the intervention did not display change in sexual risk behavior over time (B = −0.46; 95% CI = −0.96, 0.03; P = .07). All other groups showed a decline in sexual risk behavior over the course of the study (lower baseline risk and control condition: B = −0.91; 95% CI = −1.12, −0.61; P < .001; lower baseline risk and Hombre Seguro: B = −0.53; 95% CI = −0.95, −0.10; P = .02). In addition, the intervention effect was significant among higher-risk participants; participants who received the intervention and were at higher baseline risk significantly decreased their sexual risk more than their higher-risk counterparts who did not receive the intervention (B = −0.50; 95% CI = −0.90, −0.10; P = .01). Both groups did not significantly differ in unprotected sex with FSWs at baseline (B = 0.37; 95% CI = −0.14, 0.88; P = .16), and at 12 months Hombre Seguro higher-risk men reported marginally less unprotected sex than control group higher-risk men (B = −1.10; 95% CI = −2.24, 0.05; P = .06), with an average of 1.10 fewer unprotected sex acts with FSWs among the former compared with the latter.

FIGURE 3—

FIGURE 3—

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Change in total number of unprotexted vaginal and anal sex acts with female sex workers over time, by baseline syndemic risk level and Hombre Seguro intervention group: Tijuana, Mexico, 2010–2014.

DISCUSSION

Compared with research and prevention efforts with FSWS, virtually little has been done with male clients. Intervention programs designed to reduce the sexual risk behavior of male clients are imperative to help curb the global HIV epidemic. To our knowledge, our research is the first to evaluate such an intervention using a randomized controlled trial.

Overall, the Hombre Seguro intervention did not yield a positive outcome in terms of greater reductions over time in sexual risk behavior compared with a control group (i.e., difference of slopes). This was a surprising finding given that the Hombre Seguro intervention was designed off of our previously successful Mujer Segura intervention for FSWs in Tijuana and Ciudad Juarez, Mexico.34 However, there are a number of important differences between the populations of male clients and FSWs. For example, FSWs in Tijuana are required to be registered with the Municipal Health Department and must undergo routine HIV and STI testing.35 Therefore, we can infer that FSWs should be more motivated to change behavior and be more likely to respond to an intervention compared with male clients. Future work is necessary to further understand these differences and issues between FSWs and male clients. Our study provides the first data on a safer sex intervention for male clients and suggests that male clients might require more nuanced or targeted interventions than FSWs.

All participants did significantly become safer over time. For our study, there was no true control group—both groups received information about condom use, HIV, and STIs, and to some extent both conditions provided participants with a personalized risk assessment and plan to reduce risk. However, in contrast to the interactive intervention, the didactic control did not involve theory-driven, active skill-building elements oriented toward safer sex practices. The data suggest that these key differences between conditions yielded 2 notable effects. One, mere knowledge, awareness, and recognition of HIV/AIDS and one’s risky practices might be enough to reduce risky sexual practices with FSWs among male clients. Indeed, FSWs’ almost daily involvement in sex work, accompanied by regulation of the Municipal Health Department, might mean that FSWs are more exposed to and familiar with messages surrounding sexual health compared with their male clients in Tijuana, implying an elevated sensitivity to such messages among clients.

The second notable effect is that intervention efficacy was dependent on baseline syndemic risk. In the current research, syndemic risk moderated the effect of the intervention on sexual risk behavior. At 12 months postcounseling, the association between syndemic problems and unprotected sex was no longer significant among men in the control group. For men who participated in Hombre Seguro, reporting more syndemic problems was actually associated with fewer unprotected sex acts. To our knowledge, this is the first study to demonstrate an intervention “buffering” the negative impact of syndemic problems on HIV risk. The Hombre Seguro intervention was targeted toward reducing sexual risk behavior among male clients of FSWs in Tijuana, and our theory-based, interactive, and motivational interviewing approach meant that the counseling session was tailored to the specific individual’s issues and risk profile. Consequently, the intervention appeared to alleviate the composite negative impact of drug use, alcohol use, violence, depression, and incarceration on sexual risk. Compared with men in the control group, men in the interactive intervention who experienced higher syndemic problems benefitted most from the theory-based Hombre Seguro style of counseling.

The examination of the conditions under which, or the specific individuals for whom, an intervention is most efficacious is vital to HIV prevention intervention development. We demonstrated that although there was no overall difference between conditions in amount of behavior change over time, men who reported more syndemic problems benefitted most from the intervention. Syndemic problems have been shown to pose a significant barrier to safe sex. The Hombre Seguro intervention included theoretical elements aimed to address these types of barriers and build knowledge, motivation, self-efficacy, and behavioral skills, and was able to buffer the negative impact of syndemic problems on risky sex. Importantly, however, while our individual-level intervention might psychologically or behaviorally attenuate the effect of syndemics on risky behavior, it does not deal with syndemic problems themselves. Syndemics arise in disadvantaged and high-risk populations from systematic and structural disparities. Structural-level interventions specifically designed to reduce such disparities remain paramount to HIV prevention efforts.

The current findings should be interpreted in light of the limitations. Our randomized trial did not include a true control group, as participants in both conditions received information about HIV risk. Although we did not want to deny participants with important HIV/AIDS knowledge for ethical reasons, inclusion of a true control might have revealed a significant main effect of the intervention on sexual risk. Though unprotected sex with both FSWs and nonpaid partners would complete the “transmission bridge,” we did not examine effects on the clients’ sexual risk behaviors with nonpaid partners, as sexual risk behavior with FSWs is more consequential and relevant to public health. Tijuana, Mexico, is a unique region, and the results might not be generalizable to other male clients of FSWs outside of Tijuana. Regardless, our findings provide evidence of feasibility in increasing safer sex among male clients that might be adapted to other settings. The current research might aid the development of similar intervention programs for other populations experiencing syndemic problems.

Acknowledgments

This study was funded by the National Institute on Drug Abuse (NIDA; R01DA029008). Preparation of this manuscript was supported by a NIDA Mentored Career Development Award (K01DA036447-01). Some data herein were presented at the 20th International AIDS Conference, July 2014, Melbourne, Australia.

Human Participant Protection

Institutional review boards in the United States and Mexico approved the study protocol, which included obtaining participant informed consent.

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