Predictors of Injection Cessation and Relapse among Female Sex Workers who Inject Drugs in Two Mexican-US Border Cities

Abstract

We know little about predictors of injection drug cessation and relapse among female sex workers who inject drugs (FSW-PWID) at the US-Mexico border. Among HIV-negative FSW-PWID taking part in a behavioral intervention study in Tijuana and Ciudad Juárez, Cox regression was used to identify predictors of time to first cessation of injection, which was defined as reporting not having injected drugs for a period of 4 months or longer, and among that subset, we examined predictors of time to injection relapse. Among 440 women, 84 (19 %) reported ceasing injection during follow-up (median time to cessation = 9.3 months); of these, 30 (35 %) reported relapse to injection (median time to relapse = 3.5 months). The rate of injection cessation was lower for women reporting trading sex prior to age 18 (adj. hazard ratio (HR) = 0.64, 95 % confidence interval (CI) = 0.41-1.01), ever being sexually abused (adj. HR = 0.44, 95 % CI = 0.27-0.71), and a higher number of vaginal sex acts with casual clients (adj. HR = 0.99 per transaction, 95 % CI = 0.98-1.00). The rate of cessation was higher for women who spent more hours on the streets on a typical day (adj. HR = 1.04/h, 95 % CI = 1.01-1.08) and who lived in Tijuana vs. Ciudad Juárez (adj. HR = 2.15, 95 % CI = 1.14-4.07). The rate of relapse was higher among women reporting regular drug use with clients (adj. HR = 2.17, 95 % CI = 0.96-4.89) and those scoring higher on a risk injection index (adj. HR = 2.04, 95 % CI = 1.15-3.61). The rate of relapse was lower for FSW-PWID with higher than average incomes (adj. HR = 0.40, 95 % CI = 0.18-0.89). These findings have important implications for the scale-up of methadone maintenance treatment programs (MMTPs) in Mexico and indicate a need for gender-specific programs that address sexual abuse experiences and economic vulnerabilities faced by FSW-PWID.

Predictors of injecting cessation among a cohort of people who inject drugs in Tijuana, Mexico

“…In the only study to-date that examined IDU cessation in Mexico, 19% of female sex workers who injected drugs and participated in a behavioral intervention to promote safer sex in the context of drug use ceased IDU for at least four months during 12 months of follow-up. This study found no significant associations between drug use variables (including participation in OST) and IDU cessation (West et al, 2015).…”

“…Selection of predictor variables for inclusion in analysis was informed by available literature on IDU cessation (e.g. DeBeck et al, 2011; Evans et al, 2009; Kimber et al, 2010; Nambiar et al, 2015; Shah et al, 2006; West et al, 2015; Xia et al, 2015), with a focus on variables which we considered particularly relevant to our study setting (i.e., a middle-income country with low OST coverage). Four domains of variables were included:…”

Sex differences in the multilevel determinants of injection risk behaviours among people who inject drugs in Tijuana, Mexico

“…Although the outcome measure for this study was modelled closely after a measure used in a large intervention trial designed to reduce sexual and injection risk among PWID [25], it has not been psychometrically validated. However, it is important to note that this measure has demonstrated strong predictive validity [26,27], and internal consistency. Responses on HIV‐risk behaviours from female PWID may be subject to differential misclassification bias [58,59], which can arise from stigma among women who use drugs [16,60].…”

“…The primary outcome of interest was an ‘injection risk score’, which was modelled closely after a composite variable created for the Drug User's Intervention Trial [25], and has demonstrated strong predictive validity in prior research [26,27]. This score was calculated from an index of five Likert‐scaled variables assessing the frequency of injection risk behaviours in the past 6 months.…”

Gender matters? How does gender shape risk environment for syringe sharing among people who inject drugsin northern Mexico. Results from a cross-sectional survey

“…The higher HIV prevalence among WWID could be partly explained by the overlap between sex work and drug use networks (Sherman, Latkin, & Gielen, 2001;Evans et al, 2003;Strathdee, Magis-Rodriguez, Mays, Jimenez, & Patterson, 2012), in conjunction with the structural poverty conditions women face in Mexico (Patterson et al, 2006;Strathdee et al, 2008;Strathdee et al, 2013), and the highest exposure of WWID to violence (Beletsky et al, 2013;Syvertsen et al, 2014;West et al, 2016). In addition, the biologically transmission of HIV is more efficient from man to woman than vice versa (Strathdee & Stockman, 2010).…”