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Crystal Methamphetamine Use Among Female Street-based Sex Workers : Moving Beyond Individual-Focused… Shannon, Kate; Strathdee, Steffanie A.; Shoveller, Jean; Zhang, Ruth; Montaner, Julio; Tyndall, Mark Jan 31, 2011

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CRYSTAL METHAMPHETAMINE USE AMONG FEMALE STREET-BASED SEX WORKERS: MOVING BEYOND INDIVIDUAL-FOCUSED INTERVENTIONSK Shannon1,3, SA Strathdee2, J Shoveller3, R Zhang1, JS Montaner1, and MW Tyndall11British Columbia Centre for Excellence in HIV/AIDS, St. Paul’s Hospital, 608-1081 BurrardStreet, Vancouver, BC, CANADA, V6Z 1Y62Centre for Global Public Health, University of California San Diego School of Medicine, La Jolla,CA 92093-0507, United States3School of Population and Public Health, University of British Columbia, 5804 Fairview Avenue,Vancouver, BC, CANADA, V6T 1Z3AbstractGiven growing concern of the sexual risks associated with crystal methamphetamine use and thedearth of research characterizing the use of methamphetamine among street-based sex workers(FSWs), this study aimed to characterize the prevalence and individual, social, and structuralcontexts of crystal methamphetamine use among FSWs in a Canadian setting. Drawing on datafrom a prospective cohort, we constructed multivariate logistic models to examine independentcorrelates of crystal methamphetamine among FSWs over a two-year follow-up period usinggeneralized estimating equations. Of a total of 255 street-based FSWs, 78 (32%) reported lifetimecrystal methamphetamine use and 24% used crystal methamphetamine during the two-yearfollow-up period, with no significant associations between methamphetamine use and sexual riskpatterns. In a final multivariate GEE model, FSWs who used crystal methamphetamine had ahigher proportional odds of dual heroin injection (adjOR = 2.98, 95%CI: 1.35–5.22), having aprimary male sex partner who procures drugs for them (adjOR = 1.79, 95%CI: 1.02–3.14), andworking (adjOR = 1.62, 95%CI: 1.04–2.65) and living (adjOR = 1.41, 95%CI: 1.07–1.99) inmarginalized public spaces. The findings highlight the crucial need to move beyond the individualto gender-focused safer environment interventions that mediate the physical and social riskenvironment of crystal methamphetamine use among FSWs.Keywordsmethamphetamine use; gender inequities; street-based sex workers; risk environment; saferenvironment interventionsSend correspondence to: Kate Shannon, [PhD, MPH], B.C. Centre for Excellence in HIV/AIDS, Assistant Professor, Faculty ofMedicine, University of British Columbia, St. Paul's Hospital, 608-1081 Burrard Street, Vancouver, B.C., V6Z 1Y6, Canada, Tel:604-806-9459, Fax: (604) 806-9044, gshi@cfenet.ubc.ca.Contributors:KS had full access to the data, conceptualized the paper and analyses, wrote the initial draft, and was responsible for integrating all co-authors feedback. RZ conducted the statistical analyses. All authors provided feedback on the manuscript and approved the finalversion.Conflict of interest:Nothing declared.NIH Public AccessAuthor ManuscriptDrug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.Published in final edited form as:Drug Alcohol Depend. 2011 January 1; 113(1): 76–81. doi:10.1016/j.drugalcdep.2010.07.011.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscript1. INTRODUCTIONClose to 25 million people worldwide are estimated to use methamphetamine andamphetamine (United Nations Office of Drugs and Crime, 2007) and many urban centresacross North America are experiencing a significant increase in use of crystalmethamphetamine (CM) (Buxton and Dove, 2008). Methamphetamine use has beenassociated with multiple adverse health outcomes, and interpersonal risks such as self- harmand violence (Boddiger, 2005; Buxton et al., 2008; Newman et al., 2004 and Semple et al.,2004b), which represent a heavy social burden to communities (Brouwer et al., 2006 andSwanson et al., 2007). Unlike other illicit drugs, such as cocaine or heroin that are producedand/or refined outside North America, CM can be produced locally and inexpensively usingeasy-to-access precursor chemicals. Due to the widespread availability of crystalmethamphetamine, it has been suggested that conventional drug control strategies will likelyprove ineffective at curbing its widespread use (Wood and Kerr, 2008). As such, evidence isurgently needed to help characterize the social context and risk environment of CM use in aneffort to design tailored policies and interventions.Importantly, while CM use has been well described among men who have sex with men(MSM) and lesbian, gay, bisexual and transgendered (LGBT) populations, less attention hasbeen paid to female heterosexual users of crystal methamphetamine, particularly female sexworkers (FSWs). Two recent reviews of methamphetamine use have documented a moreequal sex ratio of female to male users as compared to other illicit drugs, as well assignificant gender differences in the social context of methamphetamine use (Cohen et al.,2007 and Dluzen and Liu, 2008). A few studies among women who use drugs have shownCM use to be associated with elevated concomitant sexual risks, including greater number ofsexual partners, unprotected vaginal and/or anal sex, and exchanging sex for money or drugs(Lorvick et al., 2006, Semple et al., 2004a and Weiser et al., 2006).The effects of CM have been shown to increase sexual desire, arousal, and pleasure(Patterson et al., 2005, Case et al., 2008 and Cohen et al., 2007; Dluxen et al., 2008). CMused has been linked to heightened sexual performance, particularly among MSMpopulations. Dependent CM use is commonly associated with loss of inhibitory control ofsexual behaviour and sexually compulsive behaviour, with increased risk for HIV and othersexually transmitted infections (STIs). Incidental or episodic psycho-stimulantmethamphetamine use is also reportedly widespread among some populations and isfrequently used to facilitate staying awake for extended periods of time and heightenedperiods of sexual activity and risk, including greater number of sexual partners andexchanges, risky sexual practices, and decreased condom use. Given the established linksbetween CM use and sexual risk taking, it has been increasingly postulated that CM use maybe an important and unique drug within sex work and client populations. A recent study intwo Mexico–US border cities found a 3-fold elevated odds of HIV infection among FSWswho used methamphetamine, even after adjustment for direct injection risks (Patterson et al.,2008). The authors hypothesized that non-injection methamphetamine use was a proxy forincreased HIV acquisition through unprotected sex. Qualitative work among the sex workersin these settings further suggested that CM use was used as an occupational stressor used tofacilitate staying awake and to enhance sexual performance (Crux et al., 2006).Despite the growing concerns of CM use among FSWs in many western cities across NorthAmerica and the hypothesized links between CM use and sexual risk among FSWs who usedrugs, there has been surprisingly limited attention paid to the use of CM among sex workpopulations. We therefore undertook this analysis to examine the prevalence and correlatesof CM use among a prospective cohort of street-based FSWs. In doing so, we aimed toShannon et al. Page 2Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptinvestigate the hypotheses that CM use would be associated with both enhanced sexual riskswith clients and specific environmental–structural contexts among street-based FSWs.2. METHODS2.1. Study population and samplingData are drawn from a community-based HIV prevention research partnership that has beendescribed in detail elsewhere (Shannon et al., 2007a and Shannon et al., 2007b). Briefly,between 2006 and 2008, street-based FSWs were enrolled into an open prospective cohortand participated in baseline and six monthly follow-up visits, including an interviewquestionnaire and voluntary HIV screening. Based on previous research that identified 100%substance use among street-based FSWs in Vancouver (Shannon et al., 2007a and Shannonet al., 2007b), eligibility criteria was defined as being a woman (≥14 years) who used illicitdrugs (excluding marijuana) and engaged in street-level sex work. Given the difficulties inaccessing a representative sample of FSWs due to the unknown size and boundaries of thispopulation, initial mapping of working areas with over 60 FSWs identified sex work ‘strolls’for targeted outreach and recruitment. Time-space sampling (Stueve et al., 2001) has beendeveloped as a recruitment strategy where the sampling unit is location and time wherepeople congregate rather than individuals. Similar to earlier studies of time-space samplingamong MSM in gay clubs, we systematically sampled all female sex workers (inclusive oftransgender women) through outreach at staggered times and locations along the mappedsex work strolls over the baseline period.2.2. Study instrumentsAt baseline and follow-up visits, a detailed semi-structured questionnaire administered bytrained peer researchers (former/current FSWs) elicited responses related to demographics,health service use, working conditions, violence, and sexual and drug risk practices. Inaddition, voluntary HIV screening using the point of care rapid INSTI test (Biolytical,Vancouver, Canada, specificity 99.3%, sensitivity 99.6%) was conducted by the projectnurse, supported by pre/post-test counseling. HIV-positive tests were confirmed by Westernblot.2.3. MeasuresSince we had repeated measures available over a two-year period, we analyzed datalongitudinally. The dependent variable for all analyses was derived to capture any use ofCM in the past six months (injection/smoking/snorting or other). In sub-analyses, initialexperiences of CM use were examined, including median age of first use, person with whomthey first used CM (e.g., partner, client, friend, family, dealer, pimp, stranger) and mode offirst administration (injection/smoking/snorting or other).The covariates of CM use were categorized as: (a) individual (e.g., non-modifiablecharacteristics; current behaviour patterns); (b) interpersonal (e.g., social relations andinteractions); and (c) environmental–structural (e.g., socio-spatial features; regulatory/legalfactors). Individual variables included: age (youth ≤24 years), HIV serostatus, and use ofother injection/non-injection drugs (cocaine or heroin injection, or crack cocaine smoking).Given prior evidence of enhanced sexual and drug-related harms among Aboriginal womenand youth who use drugs in this setting, Aboriginal ethnicity (e.g., First Nations, Metis orInuit ancestry) also was considered as a covariate.Interpersonal sexual and drug-related risk practices included physical violence, sexualviolence, being pressured into unprotected sex, and borrowing a used crack pipe and/orsyringe. Based on previous qualitative research (Shannon, 2008), we also examinedShannon et al. Page 3Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptcorrelates related to the interpersonal impacts of FSWs’ intimate partners, including: havingan intimate male partner who injects drugs; engaging in unprotected vaginal or anal sex witha primary partner; and having a male intimate partner procure drugs for FSWs. In addition,we examined risks specific to sex work transactions, including: median number of clientsper week, unprotected sexual transactions, client-perpetrated violence, exchanging sex whilehigh on drugs, and sharing drugs with clients.Environmental–structural factors included: homelessness; working area (industrial area,main streets, residential setting); place of servicing client (car or outdoor public space ascompared to indoor settings, including hourly rooms or saunas); harassment by police(reported as: ‘jacked up’ by police and/or confiscation of drug use paraphernalia withoutarrest); and displacement to outlying areas due to street policing (reported as: ‘having movedworking areas away from main streets due to policing’).2.4. Statistical analysesAnalyses included FSWs who completed baseline and at least one follow-up visit over thetwo-year period. Baseline variables considered included demographic variables (e.g., age,ethnicity). All other variables were treated as time-updated covariates that referred toexperiences occurring during the previous six-month period. Fisher's exact test was alsoused to compute p-values when observations were ≤5.We examined bivariate associations and tested for potential collinearity or effect-modification between individual, partner, environmental–structural variables and CM useusing generalized estimating equations (GEE) and a working correlation matrix. We usedGEE for binary outcomes with logit link for the analysis of correlated data since the factorspotentially associated with CM use during follow-up were repeated (time-dependent)measures. GEE models account for the correlation between repeated measures for eachsubject, and data from every participant follow-up visit were considered in the analyses. Wethen fit multivariate logistic GEE models adjusting for known or potential confounders andvariables that retained significance at p < 0.01 with CM use in bivariate analyses. The finalmultivariate model includes variables that retained significance at alpha level of p < 0.05.All reported p-values are two-sided, and are reported at 95% confidence intervals (CIs).3. RESULTSA total of 255 street-based FSWs completed at least one follow-up visit and were thereforeincluded in the analyses (median visits = 2, interquartile range [IQR]: 1–3). Approximatelyhalf (48%) self-identified as Aboriginal as compared to 43% Caucasian, 9% other minority(Hispanic, Asian), with no statistically significant differences in odds of CM use by ethnicity(p = 0.24). The median age at baseline was 36 years (IQR: 25–41) and the median age of sexwork initiation was 15 years (IQR: 13–21). Twenty percent were youth 24 years of age orless, with 30% of youth reporting current CM use as compared to 18% of FSWs ≥25 years(p = 0.04). HIV prevalence among FSWs was 23%, with no statistically significantdifference in likelihood of CM use by HIV status (p = 0.83). FSWs reported a mean of 12and a median of 6 clients per week (IQR = 3–15). There was no statistically significantdifference in number of clients by CM use among FSWs (p = 0.38).Of the 255 women, 78 (32%) reported lifetime CM use and 24% used CM over the two-yearfollow-up period (12% by injection only, 9% by both injection and non-injection, 3% bynon-injection only). Table 1 describes the portion of individual, interpersonal andenvironmental/structural risk events reported by FSWs, stratified by CM use over the two-year follow-up period.Shannon et al. Page 4Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptInjection was the primary mode of administration of CM use over the follow-up period(85%), in addition to non-injection (48%). However, only 40% (n = 31) first used CM byinjection, while 47% (n = 37) first smoked and 13% (n = 10) first snorted (‘bumped’) crystalmethamphetamine. The median age of initiation of CM use was 22 years (IQR: 16–34 years)while the median age of first injecting drugs was 17 years (IQR: 15–23 years), reflecting therelatively recent introduction of CM use in this setting. The most frequently reported personwith whom FSWs first used CM was a primary non-commercial sex partner (51%), followedby friend/acquaintance (22%) (p < 0.001).In univariate GEE analyses (Table 2), FSWs who used CM in the prior six months had ahigher proportional odds of injecting heroin (unadjOR = 3.11, 95%CI: 1.65–5.98), having anintimate sex partner who injects drugs (unadjOR = 2.03, 95%CI: 1.20–3.42), injectingcocaine (unadjOR = 2.00, 95%CI: 1.06–3.18), being ≤24 years of age (unadjOR = 1.91,95%CI: 1.01–3.61), working in an industrial area (unadjOR = 1.68, 95%CI: 1.06–2.67), andliving on the street (unadjOR = 1.53, 95%CI: 1.15–2.15). FSWs who used CM had a lowerproportional odds of smoking crack cocaine (unadjOR = 0.58, 95%CI: 0.33–1.03).In a final multivariate GEE model (Table 3), FSWs who used CM in the prior six monthshad a higher proportional odds of being a heroin injector (adjOR = 2.98, 95%CI: 1.35–5.22),having a primary male sex partner who procured drugs for them (adjOR = 1.79, 95%CI:1.02–3.14), working in industrial areas (adjOR=1.62, 95%CI: 1.04–2.65), and living on thestreet (adjOR=1.41, 95%CI: 1.07–1.99).4. DISCUSSIONClose to one-third of our sample reported lifetime CM use, with one quarter using CM useover the two-year follow-up period. Over half of FSWs who use methamphetamine reportedfirst using CM with a primary non-commercial sex partner, and we observed two foldincreased odds of CM use among FSWs who had a primary sex partner who procured drugsfor them. Further, CM use remained independently associated with working and living inmarginalized public spaces.Importantly, our findings contrast with earlier hypotheses that CM use among FSWs mayfacilitate enhanced sexual risks, with no statistically significant associations observedbetween CM use and number of clients, or unprotected sex with clients or non-commercialpartners among FSWs. These findings however do not discount the potential use ofmethamphetamine as an occupational stressor among sex workers, as observed in northernMexican border cities, where methamphetamine use among FSWs is associated withoccupational stressors, such as the need to stay awake (Cruz et al., 2007).Instead, in this study of street-based FSWs, CM use appears to be more important within thecontext of intimate drug-using sexual partnerships suggesting a gendered pattern of riskcolliding along the intersections of street-based sex and drug markets. These findings accordwith the limited qualitative research (Cruz et al., 2007) suggesting that CM use amongFSWs may be most closely tied to use with spouses and other trusted, non-commercial sexpartners, who may act as pimps. In this study, the particularly nuanced relationship of drugprocurement by primary male sex partners of FSWs may confer a gendered risk environmentof CM use within sexual partnerships, as previously described among crack users over thelast two decades (Maher, 1997). In particular, qualitative accounts of crack-using primarypartnerships have consistently documented gendered risk environments, including risk ofinfectious disease transmission, among younger FSWs who work to obtain the money fordrugs for both themselves and their partner and rely on older male partners (often serving aspimps or sugar daddies) to procure drugs for them (Shannon et al., 2008; Maher 1997). ThisShannon et al. Page 5Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptemerging pattern of risk among FSWs who use CM rely on male sex partners to procuredrugs for them extends earlier work suggesting that CM use may substitute cocaine as acheaper or more easily accessible stimulant in settings with a proximal vulnerability to anestablished stimulant drug use pattern (Case et al., 2008). Further, though the results did notremain significant in multivariate analyses, FSWs who use CM in our study were marginallyless likely to smoke crack cocaine suggesting a potential shift in stimulant use may beemerging in this population.Qualitative research studies among heroin and cocaine-using couples have demonstratedhow drug user's sexual relationships can act as key sites of risk management that directlymodify individual drug use practices and facilitate positive social norms ([Rhodes et al.,1998] and [Simmons and Singer, 2006]). Specifically, the overtly gendered collusion amongsexual partnerships to procure and use drugs was shown to reinforce and produceinterpersonal risks, as well as protective mechanisms (Simmons and Singer, 2006). Amongmale-female intimate partners, drug involvement has been previously found to be directlyassociated with male psychological dominance, increased physical and sexual violence andconcomitant sexual HIV risks (El-Bassel et al., 2005). Evidence also suggests that femaleIDUs tend to have greater overlap in their sexual and drug use networks relative to theirmale counterparts ([Sherman et al., 2001] and [Strathdee et al., 2008]), and drug sharingamong IDU sexual partnerships has been shown to place women at increased risk of being“second on the needle” ([Cruz et al., 2007] and [Harvey et al., 1998]). Accordingly,women's lack of control over access and procurement of drugs, including cleaning of druguse paraphernalia and ‘tasting’ the strength of the drugs, may facilitate enhanced sexual anddrug risk patterns. Women have also been shown to be more likely to: engage in syringe-mediating sharing processes such as frontloading (a method of distributing shared drugsthrough syringes); sharing other injection/non-injection paraphernalia (e.g., crack pipes);and trading unprotected sex directly for drugs ([Fernando et al., 2003], [Flinlinson et al.,2005], [Grund et al., 1996] and [Koester et al., 2005]). These findings underscore the need toscale up gender-sensitive and couple-focused harm reduction and treatment interventions,recognizing the nuanced importance of drug-using sexual partnerships in both maintainingrisky and preventative practices.Additionally, given that the majority of FSWs who use methamphetamine in this study werepoly users of heroin injection, interventions will need to account for dual opiate dependencyin shaping risk patterns and environments. Evidence among methamphetamine-using MSMhas shown CM to most be frequently used in combination with other drugs (Patterson et al.,2005), particularly heroin injection (Case et al., 2008). Users often combine drugs tominimize the adverse effects of a drug, such as countering the undesirable “crashing” effectsof methamphetamine (Patterson et al., 2005). Anecdotal reports suggest thatmethamphetamine may be used to provide a ‘kick’ when heroin purity decreases. Poly-druguse has been shown to drastically elevate the potential for drug toxicity and overdosemortality, as well as transient immune suppression (Leri et al., 2003), which may help tofurther explain recent findings of elevated risk of non-fatal overdopes among CM injectors(Fairbairn et al., 2008).Collectively, these findings suggest the potential for an emerging outbreak of amethamphetamine epidemic consistent with the “social equation of risk” of stimulant CMuse previously conceptualized in other settings such as Tijuana, Mexico (Case et al., 2008).The established components of this social equation of risk have been postulated to includeproximal vulnerability to established stimulant drug use patterns; social dislocation due toeconomic disparities, migration or poverty; an available supply and locally produced ormanufactured drug; and geographic proximity to drug use environment (Case et al., 2008).Of particular importance, our findings suggest that CM use is closely linked to street-basedShannon et al. Page 6Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptsex work in marginalized public spaces, suggesting social dislocation and features of thephysical and social environment may shape access and availability of CM use or specificsocial networks and socio-spatial patterns of CM use. While further exploration is needed ofthe contexts of space that may shape CM patterns among FSWs, their partners and clients,these findings point to the critical need for policies and interventions that modify the riskenvironment (Rhodes, 2002) and ensure safer sex work spaces in proximity to harmreduction and treatment resources. While CM use in our study was not associated withspecific sexual risk patterns, the use of CM by FSWs in more marginalized public spacesmay point to potential pathways to sexual risk. For example, we have previously observedelevated rates of coercive unprotected sex by clients among street-based FSWs displaced toworking in industrial settings (Shannon et al., 2008). As such, structural interventions thatmitigate the risk environment of street-based sex work (such as safer sex work sites andscaled up mobile outreach interventions to outlying and isolated spaces) may help toneutralize the gendered nature of drug acquisition and co-dependence in these sexualpartnerships.Strengths and limitations: the self-reported nature of responses may have been subject tosocial desirability biases that could have underestimated risky sexual and drug use practicesand attenuated results towards the null. Secondly, the observational nature of this researchprecludes determining causality, although the longitudinal analyses using GEE may accountfor the impact of repeated measures and temporal bias. Thirdly, the relatively small samplesize may have diluted our ability to detect associations, such as the association betweenmethamphetamine use and younger age. Finally, our results may not be generalizable toFSWs working in indoor venues, such as massage parlours or escort agencies.In summary, our findings suggest the potential of an emerging CM epidemic among street-based FSWs and their non-commercial partners with the that the greatest concentration ofharms among FSWs working and living in marginalized public spaces. As such, thisresearch highlights the critical importance of safer environment interventions that mediatethe risk environment and context of CM use in reducing harms, including gender-sensitiveand couple-focused interventions that tailored to FSWs and their intimate drug-usingpartners.REFERENCESBoddiger D. Methamphetamine use linked to rising HIV transmission. 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New York: United Nations; 2007.Available: www.unodc.org/docuemnts/data-and-analysis/WDR-2007-exsum.pdfWeiser SD, Dilworth SE, Neilands TB, Cohen J, Bangsberg DR, Riley ED. Gender-specific correlatesof sex trade among homeless and marginally housed individuals in San Francisco. J. Urban Health.2006; 83:736–740. [PubMed: 16845499]Wood E, Kerr T. Methamphetamine strategy requires evaluation. CMAJ. 2008; 179:677. [PubMed:18809901]Shannon et al. Page 9Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptShannon et al. Page 10Table 1Individual, interpersonal and contextual characteristics of street-based FSWs, stratified by crystalmethamphetamine use over two-year follow-up.Characteristic Crystal methamphetamine useYes(n = 105)an (%)No(n = 493)an (%) p-valueIndividual factorsCocaine Injection 42 (40) 130 (26) 0.030Heroin Injection 68 (65) 195 (39) <0.001Crack Smoking 66 (63) 425 (86) 0.063Interpersonal factorsPressured into sex without a condom 30 (29) 115 (23) 0.968Borrowed use crack pipe and/or syringe 62 (59) 301 (61) 0.275Experienced physical violence 24 (22) 127 (26) 0.221Experienced sexual violence 20 (19) 83 (17) 0.418Intimate partner riskIntimate partner who injects drugs 31 (30) 111 (26) 0.141Intimate partner who procures drugs 31 (30) 52 (11) 0.007Unprotected sex with an intimate partner 25 (22) 95 (19) 0.945Sexual transactions with clientsMedian number of clients/week (IQR) 6 (2–14) 6 (3–15) 0.382Unprotected sexual transactions 27 (26) 99 (20) 0.645Shared drugs with clients 45 (43) 187 (38) 0.578Exchanged sex while high 45 (43) 260 (53) 0.391Experienced client-perpetrated violence 19 (18) 93 (19) 0.178Environmental–structural factorsAbsolute homelessness (lived on the street) 50 (48) 183 (37) 0.010Worked in an industrial area 28 (27) 73 (14) 0.002Serviced clients in cars or public spaces 62 (59) 264 (54) 0.493Moved working areas to outlying spaces due to street-policing 36 (34) 203 (41) 0.726Experienced police harassment/confiscation of drug use paraphernalia (without arrest) 44 (42) 172 (35) 0.493aRefers to total number of reports over two-year follow-up period. Fisher's exact test was used to compare proportions if one or more counts wasless than or equal to five.Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptShannon et al. Page 11Table 2Bivariate GEE analyses for individual, interpersonal, and contextual factors correlated with crystalmethamphetamine use among street-based FSWs (n = 255) over two-year follow-up.Characteristics Crystal methamphetamine useCrude oddsratios95% ConfidenceintervalsIndividual factorsYouth (≤24 years of age) 1.91 (1.01–3.61)Aboriginal ethnicity 0.70 (0.38–1.27)HIV seropositive 1.07 (0.55–2.09)Cocaine injection 2.00 (1.06–3.18)Heroin injection 3.11 (1.65–5.91)Crack cocaine smoking 0.58 (0.33–1.03)Interpersonal factorsPressured into sex without a condom 1.01 (0.65–1.58)Borrowed use crack pipe and/or syringe 1.21 (0.86–1.71)Experienced physical violence 1.03 (0.69–1.59)Experienced sexual violence 1.36 (0.65–2.84)Intimate partner risksIntimate sex partner who injects drugs 1.33 (0.91–1.97)Intimate sex partner who procures drugs 2.03 (1.20–3.42)Unprotected sex with intimate partner 0.99 (0.66–1.46)Sexual transactions with clientsMedian number of clients/week 0.99 (0.97–1.01)Unprotected sexual transactions 1.11 (0.72–1.72)Shared drugs with clients 1.11 (0.72–1.61)Exchanged sex while high 0.82 (0.52–1.29)Experienced client-perpetrated violence 0.67 (0.38–1.19)Environmental–structural factorsAbsolute homelessness (lived on the street) 1.53 (1.15–2.15)Worked in industrial areas 1.68 (1.06–2.67)Serviced clients in cars or public spaces 1.15 (0.78–1.70)Moved working areas to outlying spaces due to street-policing 0.93 (0.61–1.42)Experienced police harassment/confiscation of drug use paraphernalia 1.15 (0.77–1.71)Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptShannon et al. Page 12Table 3Multivariate GEE analyses for individual, interpersonal, and contextual factors independently correlated withcrystal methamphetamine use among street-based FSWs (n = 255) over two-year follow-up.Characteristics Crystal methamphetamine useAdjusted odds ratios 95% Confidence intervalsHeroin injectiona 2.98 1.35–5.22Youth (≤ 24 years of age) 1.80 0.90–3.63Intimate partner who procures drugsa 1.79 1.02–3.14Worked in industrial areasa 1.62 1.04–2.65Cocaine injection 1.50 0.87–2.51‘Absolute homelessness’ (lived on the street)a 1.41 1.07–1.99Crack cocaine smoking 0.67 0.40–1.15aVariables that retained significance at p < 0.05 in the multivariate GEE model.Drug Alcohol Depend. Author manuscript; available in PMC 2012 July 09.


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