Infectious Diseases of Poverty volume 10Article : 7 Cite this article. Metrics details. Male sex workers are at high-risk for acquisition of sexually transmitted infections STIsincluding human immunodeficiency virus HIV. We quantified incidence rates of STIs and identified their time-varying predictors among male sex workers in Mexico City. From January to Maymale sex workers recruited from the largest HIV clinic and community sites in Mexico City were tested for chlamydia, gonorrhea, syphilis, hepatitis, and HIV at baseline, 6-months, and months.
We examined potential time-varying predictors using generalized estimating equations for a population averaged model. Incidence rates per person-years were as follows: HIV [5.
Consistent condom use is an important protective factor for STIs, and should be an important component of interventions to prevent incident infections. The prevalence of human immunodeficiency virus HIV in Mexico is 0. Studies at the global level have shown that, despite a decline in HIV infection in recent years among the general adult population, HIV acquisition among MSWs has increased [ 3 ].
In part, this is a result of higher transmissibility of HIV during anal intercourse, as well as other risk factors among MSWs, including multiple sexual partnerships, membership in dense sexual networks, and limited access to healthcare services due to stigma [ 45 ]. Information is also limited because MSWs are a highly vulnerable and stigmatized population, leading few MSWs to openly disclose their occupation as sex workers [ 910 ]. For the purposes of this study, MSWs are defined as cisgender men, ages 18—40, who either self-identified as MSWs or who did not self-identify as MSWs, but who declared that they were a man who had sex with a male partner in exchange for money in the past six months and who had at least 10 male sexual partners within the last month.
A detailed description of the study population and methods is available elsewhere; a brief overview is provided here [ 119 ]. We conducted this secondary analysis because there is a dearth of information about prevalence and incidence of STIs among MSWs. This study took place from January to May Participants were recruited by trained research staff from community sites where MSWs were known to congregate in Mexico City, as determined in studies [ 1920 ].
Treatment was provided free of charge, including antiretroviral treatment for those identified as HIV-positive. All participants provided informed consent.
These criteria were determined based a study involving observations and in-depth interviews with sex workers in Mexico City [ 20 ]. At the baseline visit, participants filled out a survey with questions regarding sociodemographic characteristics and health behaviors. At baseline 0 months and Mexico visits one 6 months and two 12 monthsparticipants filled out the survey again and were tested and treated as indicated for syphilis, chlamydia, gonorrhea, condoms HIV.
Participants were administered the survey using laptop computers with audio computer assisted interviewing A-CASI questionnaires. All variables were assessed for missingness, range, and distribution. Blood and urine samples were obtained from the participants using bio-safety protocols. Samples were analyzed by trained laboratory personnel. At the baseline survey, two subgroups were defined for the markers of syphilis and hepatitis B: antibody positivity was regarded as a lifetime marker of past or present infection, whereas treponemic antibody positivity together with VDRL demonstrated active syphilis, and anti-HBc plus HBsAg positivity indicated current hepatitis B virus infection.
Based on findings from prior literature and known associations between specific sexual risk behaviors and incident STIs, we created a conceptual framework free likely predictors, the majority of which were time-varying, and included: age, education, drug use, condom use, and frequency and types of sexual [ 721 ].
Subjects, materials, and methods
The demographic variable age was continuous and the other demographic variable, highest educational attainment, was categorical. Four separate variables were included to describe sexual activity: had vaginal, anal, or oral sex with clients last week; had vaginal, anal, or oral sex with non-paying partners in the past week; had insertive anal sex with any of three most recent clients; and had receptive anal sex with any of three most recent clients.
The first two variables describing sexual activity were continuous variables and the latter two were binary variables.
Consistent condom use during sex in the past month and drug use with any of three most recent clients were similarly coded as binary variables. See Additional file 1 for further details on each of these variables. Lastly, since this study is a secondary analysis of a RCT that evaluated the impact of conditional economic incentives on staying free of new curable STIs, a variable for randomization to the four study arms of the original RCT was included in our model.
Incidence and time-varying predictors of hiv and sexually transmitted infections among male sex workers in mexico city
This controls for the effect of incentives and conditionalities. Detailed descriptions of the main covariates and outcomes variables in this study are provided in Additional file 1. Income and wealth were not included in the model because nonresponse was high for these variables.
Incidence rates were estimated using the person-time method i. We chose this method because it yields appropriate confidence intervals even with relatively small sample sizes. Participants lost to follow-up stopped accruing person years at their last known study visit.
To calculate person-time for seroconversions that happened during follow-up intervals, we took the midpoint of the follow-up interval as an estimate of the time at which seroconversion occurred. During the course of the study, 43 participants were lost to follow up at the 6-month visit and an additional 25 participants were lost to follow up at the month visit. A detailed analysis of loss to follow up for this cohort was conducted in a study [ 24 ].
Participants with prevalent STIs at baseline were excluded for the STIs for which they tested positive, but were still included for calculations of incident STIs for which they tested negative at baseline.
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We estimated marginal models using generalized estimating equations GEE with a logit link and binomial variance to examine unadjusted and multivariable-adjusted time-varying predictors of incident STIs [ 25 ]. The GEE model provides marginal estimates, for which the estimate is averaged over all values of the covariates, which could be correlated. All models used an unstructured correlation structure. The of our present GEE model are conditional on returning to the Clinic for follow-up.
We used quasi-likelihood independence model criterion QIC to select the best working correlation structure and the best subset of covariates as diagnostic measures of model fit [ 26 ]. Sociodemographic and behavioral characteristics at baseline are shown in Table 1.
MSWs had a median of three sexual partners in the last week. The total amount of follow-up time for the study cohort was The highest incidence rates were for active syphilis In the unadjusted GEE models, the odds of incident STIs did not vary ificantly by older age, school education, of clients the individual had sex with in the past week, of non-paying partners the individual had sex with in the last week, drug use, condom use, provision of insertive anal sex, or provision of receptive anal sex Table 3.
The associations between time-varying predictors and incident STIs are also presented as incident-rate ratios in Additional file 2with the direction and magnitude of associations being very similar to the findings from our primary analyses presented in Table 3.
Our final model had the second smallest QIC criterion-indicative of model fit.
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The adjusted model without the covariate on of non-paying sexual partners had a slightly smaller QIC than the final model that we used We chose to include the variable on of non-paying sexual partners because it is an important covariate in the literature; as such, we were balancing formal goodness-of-fit measures with epidemiological theory.
In the adjusted multivariable regression models, the only two predictors found to be ificant were age and consistent condom use. Increasing age was a risk factor for incident STIs.
Conversely, consistently using condoms during anal or vaginal intercourse was protective for incident STIs. studies of urban, MSM populations have found a similar correlation between consistent condom use and reduced incident STIs. It is important to note is that some participants were recruited into our study by referral from within Condesa HIV Testing Clinic and, furthermore, that participants had to agree to frequent HIV and STI testing as part of the research protocol. This means study participants likely have a greater concern and interest in their sexual health than the general MSWs population in Mexico City.
As such, we expect our estimates for protective health behaviors, such as condom use, to be overestimates, and we expect estimates for risky health behaviors, such as drug use during sex work, to be underestimates when compared to the general MSWs population in Mexico City.
Furthermore, procurement prices continue to be higher in Mexico than other Latin American countries, which can be a deterrent to larger scale PrEP implementation [ 3133 ]. Since only a small of MSWs reported consistently using condoms during anal and vaginal sex The Avahan Program—a large-scale HIV prevention program in southern India—combines peer-mediated strategies, condom distribution and STI clinical services to improve outcomes in high-risk men who have sex with men [ 27 ].
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Increased condom use free commercial and non-commercial partners, as well as decreased syphilis incidence, was strongly linked with exposure to this program. In other low- and middle-income countries, evidence-based interventions for increasing condom use in sex Mexico populations demonstrate that reducing STI transmission is more effective when combined with the consistent and correct use of condoms [ 394041 ].
This suggests that behavioral interventions for primary STI and HIV prevention may also serve to enhance the effectiveness of secondary prevention activities. The primary limitation of our study was the calculation condoms incidence rates using data from a randomized controlled trial of economic incentives to reduce risky sexual practices [ 1 ]. Therefore, our should be interpreted as conservative estimates. Another limitation of the study was the small sample size, which decreased the precision of our estimates and increased the likelihood of type II error, a failure to detect a difference that was present within our sample.
Some participants were lost-to-follow-up after the first and second study appointments, which further reduced the sample size. The smaller sample size, however, did allow us to collect higher quality data on STIs and potential predictors. Lastly, it is important to reiterate that it was only in our multivariable adjusted model that we found ificant associations between incident STIs and predictors. Our unadjusted model did not find these associations ificant.
One last element we would like to note is that our final data collection took place in May Although there have inevitably been changes to the field of HIV and in Mexico City since then, the of this study are still relevant. To the best of our knowledge, this is the only study that provides these incidence rates for MSWs in Mexico City. Furthermore, prevention and early detection of HIV are both as important as ever. Consistently using condoms during anal and vaginal sex was found to be associated with a lower likelihood of STI acquisition among these MSWs.
Consistent condom use appears to be a key potential predictor of STIs and is an important component of interventions to prevent infections. Additionally, targeted interventions for MSWs who report inconsistent condom use are warranted in light of these findings.
Given such high HIV rates within this MSWs population, the population would likely benefit from future work that assesses the feasibility, effects, and cost of incorporating PrEP in multidimensional interventions. Article Google Scholar. HIV prevalence and risk behavior from a nationally representative survey among men who have sex with Men. PLoS One. Male sex workers: practices, contexts, and vulnerabilities for HIV acquisition and transmission. J Acquir Immune Defic Syndr.