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. Author manuscript; available in PMC: 2024 Feb 1.
Published in final edited form as: Int J Drug Policy. 2023 Jan 13;112:103950. doi: 10.1016/j.drugpo.2022.103950

ASSOCIATION OF SEX WORK AND SOCIAL-STRUCTURAL FACTORS WITH NON-FATAL OVERDOSE AMONG WOMEN WHO USE DRUGS IN VANCOUVER, CANADA

Miriam TH Harris a,b, Shira Goldenberg c,d,e, Zishan Cui e,f, Nadia Fairbairn e,f, M-J S Milloy e,f, Kanna Hayashi e,f,g, Jeffrey H Samet a,b, Alexander Y Walley a,b, Seonaid Nolan e,f
PMCID: PMC9974922  NIHMSID: NIHMS1865997  PMID: 36640591

Abstract

Background

Women who use drugs (WWUD) and engage in sex work experience disproportionate sex- and drug-related harms, such as HIV, however comparatively little is known about their overdose risk. Therefore, we examined the association between sex work and overdose and secondarily explored the association of social-structural factors, such as policing and gendered violence, with overdose.

Methods

Data were derived from two community cohort studies based in Vancouver, Canada between 2005 to 2018. We used logistic regression with GEE to examine the associations between a) sex work and nonfatal overdose and b) social-structural and individual variables with overdose among WWUD who engaged in sex work during the study. Sex work, overdose, and other variables were time-updated, captured every six months.

Results

Among 857 WWUD included, 56% engaged in sex work during the study. Forty-three percent of WWUD engaged in sex work had at least one overdose compared to 26% of WWUD who did not. Sex work was not significantly associated with an increased odds of overdose (AOR = 1.14, 95% CI: 0.93–1.40). In the exploratory analysis amongst 476 WWUD engaged in sex work, social-structural variables associated with overdose in the multivariable model included exposure to: punitive policing (OR = 1.97, 95% CI: 1.30–2.96) and physical or sexual violence (OR = 2.55, 95% CI: 1.88–3.46).

Conclusions

WWUD engaged in sex work had an increased overdose burden that may be driven by social-structural factors rather than sex work itself. Interventions that address policing and gendered violence represent potential targets for effective overdose prevention.

Keywords: overdose, women, sex work, violence, drug use

INTRODUCTION

Women who use drugs (WWUD) and engage in sex work (i.e., the exchange of sex for money, drugs, or other goods/services) experience compounding drug- and sex-related health problems. Complex reinforcing structures between drug use and sex work, such as drug use leading to sex work income dependency or drug use with clients during sex work, have been associated with drug- and sex-related health problems among WWUD (Deering et al., 2011; Duff et al., 2013; Shannon et al., 2011). Health problems include a high burden of HIV and other sexually transmitted and blood-borne infections, trauma, and physical and sexual violence (Azim et al., 2015; Decker et al., 2012; El-Bassel et al., 2020; Strathdee et al., 2015). Structural factors—including gender inequality that normalizes violence against women and sex workers, the criminalization of drug use and sex work, and stigma towards WWUD and sex workers—are also key drivers of these drug- and sex-related health problems (Boyd et al., 2018; El-Bassel & Strathdee, 2015; Hui et al., 2017; Mburu et al., 2019). However, less is known regarding overdose risk in this population. Driven by fentanyl and other toxins adulterating the drug supply, drug overdose deaths have risen dramatically across the United States and Canada, with 2021 being the deadliest year to date (Centers for Disease Control and Prevention, 2021; Ciccarone, 2017; Special Advisory Committee on the Epidemic of Opioid Overdoses, 2021). In the US, between 1999–2017 there was a 260% increase in the number of fatal overdoses among women aged 30–64 years, and 500% increase in the number of fatal overdoses among women aged 55–64 years (VanHouten, 2019). Given the threat posed by the toxic drug supply in North America and evidence that WWUD engaged in sex work experience disproportionate sex- and drug-related health inequities, further research is needed to better characterize overdose risk and potential overdose prevention strategies in this population (Ciccarone, 2017; Goldenberg, 2020; Tyndall, 2020).

Qualitative research among WWUD found that women have reduced access to overdose prevention through syringe service programs and safe consumption spaces compared to men, as these services can be male-dominated and perceived as unsafe (Boyd et al., 2018; Fairbairn et al., 2008; Harris et al., 2021). Such work has highlighted the need for women-focused harm reduction interventions. One cross-sectional study among WWUD engaged in sex work in Kazakhstan found a high burden of overdose, with 38% of women reporting a lifetime history of overdose and 18% reporting an overdose event in the last three months and intimate partner violence was strongly associated with overdose (El-Bassel et al., 2020). Another study among women engaged in sex work in Vancouver, Canada (of whom approximately 86% used stimulants and 60% used opioids) found one in three women experienced at least one non-fatal overdose over the 7.5-year study period (Goldenberg et al., 2020). This study showed that women who reported police presence as a barrier to harm reduction services had more than double the odds of experiencing a nonfatal overdose. However, few studies have examined if engaging in sex work influences overdose risk and how other social-structural factors may mitigate or increase overdose risks among WWUD engaged in sex work.

Vancouver, Canada, is the site of a large and heavily-concentrated drug use scene (Shannon et al., 2008) and is home to two longstanding community-recruited cohort studies of people who use drugs. We leveraged these cohort studies to examine non-fatal overdose among WWUD and the relationship between sex work and socio-structural factors and non-fatal overdose. Evidence from the HIV literature demonstrates HIV risks among sex workers and people who inject drugs are driven by socio-structural factors such as gender-based violence, policing, and incarceration (Azim et al., 2015; Bekker et al., 2015; El-Bassel & Strathdee, 2015; Strathdee et al., 2015). Similar social-structural factors are likely to also drive overdose risk among WWUD. This study draws on these HIV risk and prevention models (Bekker et al., 2015; Strathdee et al., 2015) to explore overdose among WWUD (See Appendix 1).

We first examined the longitudinal association between sex work engagement and overdose. We hypothesized that among WWUD, periods of engagement in sex work would have greater odds of overdose compared to periods when they were not engaged in sex work. Second, we explored the associations of social-structural and individual factors with overdose among WWUD who reported actively engaging in sex work during the study period. We hypothesized that overdose would be driven by social-structural factors such as violence, punitive policing, and access to care in the community, rather than sex work itself. Understanding the overdose burden among WWUD and potential drivers of overdose is critical to generating and implementing effective overdose prevention strategies.

METHODS

Study design and population

We used two ongoing community-recruited open prospective cohort studies, the AIDS Care Cohort to Evaluate exposure to Survival Services (ACCESS) and the Vancouver Injection Drug Users Study (VIDUS). Details regarding the ACCESS and VIDUS study design have been well-described elsewhere (Strathdee et al., 1998; Wood et al., 2009). Briefly, starting in 1996, using word-of-mouth and street-based outreach in the Downtown Eastside neighbourhood of Vancouver, people living with HIV who reported drug use other than or in addition to cannabis (ACCESS), and HIV at-risk people who reported injection drug use (VIDUS), aged ≥18 years were eligible for recruitment. Participants provide written informed consent prior to enrollment. VIDUS participants who undergo HIV seroconversion during the follow-up period are offered recruitment into the ACCESS study. The cohort procedures and questionnaires for ACCESS and VIDUS are harmonized to facilitate pooled analyses across the cohorts.

At baseline and biannually, study participants complete an interviewer-administered questionnaire and provide biosamples (blood, urine) for analysis. Study instruments capture demographic data, drug use patterns, health and social service utilization, sex work engagement, criminal-legal involvement, and experiences of physical or sexual violence. Participants who missed four consecutive interviews were considered lost to follow-up. The University of British Columbia and Providence Healthcare Research Ethics Board regularly reviewed and approved these studies.

The present study was restricted to individuals from the ACCESS and VIDUS cohorts who self-identified as a woman and completed a baseline and at least one follow-up interview from 2005 to December 2018. Participants were compensated 40 dollars (CAD) per visit. Data were restricted to 2005–2018 as sex work characteristics were not systematically collected until 2005, and analyzable data was not available beyond 2018 at the time of this study.

Outcome variable

The primary outcome of non-fatal overdose was defined as responding “yes” to the question: “In the last six months, have you overdosed by accident (i.e., where you had a negative reaction from using too much drugs or had a bad trip)?” (Caudarella et al., 2016). Intentionality was not explored. Non-fatal overdose was measured at every six-month study visit and treated as distinct observation clustered at the participant level.

Independent variable

The independent variable, sex work, was defined as responding “yes” to the question: “In the last six months, were you given any money, gifts, food, shelter, clothes, drugs, or a favour for sex?” (Chettiar et al., 2010; Kerr et al., 2016; Marshall et al., 2010). Sex work was measured at every six-month study visit and treated as distinct observation clustered at the participant level.

Confounder and exploratory variables

To guide the selection of socio-structural variables, we developed a new overdose risk framework for WWUD (Appendix 1) based on Bekker and Strathdee et al’s frameworks for HIV prevention among sex workers and WWUD, which considers individual and structural drivers of HIV infection (Bekker et al., 2015; Strathdee et al., 2015). A specific WWUD overdose framework is warranted given the unique gendered experiences and overdose prevention needs of this population (Collins et al., 2019; Goldenberg et al., 2020; Goldenberg, 2020). Our conceptual overdose risk framework considered drug supply, policy, community care access, social network, sex work, drug use behaviour, and individual factors in shaping overdose risk and prevention among WWUD. All variables described below were identified using our conceptual framework and were time-updated, measured at every six-month study visit, except for ethnicity and sexual orientation which remained fixed and were taken from the baseline visit.

To capture temporal changes in the drug supply, particularly the arrival of fentanyl, we included the calendar year as an ordinal variable (from 2005–2018) as a proxy for more reliable drug surveillance data. To capture policy factors, such as structural marginalization (Bailey et al., 2017; English et al., 2021), we included race and ethnicity defined as identifying as White versus Black, Indigenous (First Nations, Inuit, & Metis), or as a Person of Color (Hyett et al., 2018; Schnarch, 2004), and minority sexual orientation defined as self-identifying as straight versus gay, lesbian, bisexual, two-spirit, queer, asexual, or other. To capture other policy factors related to the criminalization of drug use and sex work we included being unhoused defined as experiencing homelessness (yes vs no), recent incarceration defined as being in jail or prison (yes vs no), and punitive policing defined as being stopped, searched, detained, or assaulted by the police (yes vs no).

To capture community care access we included treatment with medications for opioid use disorder (MOUD), defined as being on methadone, buprenorphine/naloxone, slow-release oral morphine, injectable opioid agonist therapy (intravenous diacetyl-morphine or hydromorphone), or naltrexone (yes vs no), utilization of supervised consumption sites defined as injecting at a supervised injection/overdose prevention site (yes vs no), and experiencing barriers to addiction care, defined as reporting being unable to access addiction treatment (yes vs no). To capture social network factors, such as gender-power imbalances, we included exposure to violence defined as physical or sexual assault (yes vs no), and being in a stable relationship defined as being legally married, or common law, or with a regular partner (yes vs no). To capture other social factors, such as drug use culture, we included living in the Downtown Eastside of Vancouver, a neighbourhood characterized by prevalent drug use, marginalization, and criminalization (yes vs no).

To capture drug use behaviours, we included opioid use defined as heroin, fentanyl, or prescription opioid use in a non-prescribed way (yes vs no), stimulant use defined as crystal/methamphetamine or crack/cocaine or prescription amphetamine use in a non-prescribed way (yes vs no), and alcohol use (yes vs no). Individual variables included age (continuous, in years).

Statistical analyses

First, we stratified participant characteristics by reporting sex work in the last six months at baseline and reported these as counts and percentages for binary variables and medians and interquartile range for continuous variables.

Non-fatal overdose prevalence and trends over time

We used descriptive statistics to summarize the proportion of bi-annual interview visits involving a non-fatal overdose in the past six months and the number of overdose events during the study period. We examined the counts and percentages of women who experienced an overdose stratified by reporting sex work in the last six months. We also assessed overdose trends over time by calculating the proportion of the bi-annual interview visits involving non-fatal overdose during each calendar year from 2005 to 2018.

Sex work association with non-fatal overdose

Our conceptual model was used to guide initial confounder selection followed by the application of a correlation matrix where overlapping variables that had a high degree of collinearity were excluded. Bivariate logistic regression was then used to examine the association between the independent variable of interest and selected confounders with non-fatal overdose over the study period. Generalized estimating equations (GEE) with a logit-link function and exchangeable correlation matrix were used to account for repeated measurements amongst participants over time (Diggle et al., 2013; Hardin & Hilbe, 2002). We then constructed an adjusted model where we included confounders that were significantly associated with the outcome at p < 0.10 in the bivariate analyses. We used a stepwise approach to fit a series of reduced models (Maldonado & Greenland, 1993; VanderWeele, 2019). After comparing the value of the coefficient of sex work associated with overdose in the full model to the value of the coefficient in each of the reduced models, we dropped the secondary variable associated with the smallest relative change. We continued this iterative process until the minimum change exceeded 5% to reach the final most parsimoniousness model. Missing and intermittent data were handled using the GEE estimating mechanism that draws on data from non-missing pairs for the estimators of its operating correlation matrix. We reported 95% confidence intervals. All statistical analyses were performed in SAS version 9.4.

Exploratory analysis of individual and social-structural variables associated with non-fatal overdose among women engaged in sex work

To explore factors associated with overdose among WWUD engaged in sex work we first restricted the analytic sample to observations in which women reported sex work in the last six months. We identified exploratory variables through the application of our conceptual framework followed by a correlation matrix to exclude highly collinear variables. We then used multiple bivariate logistic regression with GEE to examine associations between individual exploratory variables and overdose. Variables significantly associated with the outcome at p < 0.10 in bivariate analyses were included in a single multivariable logistic regression model with GEE. We applied a backward elimination approach to fit a series of reduced models to reach the final most parsimonious model associated with a minimized Quasi-Likelihood Information Criterion (QIC) value (Vittinghoff et al., 2006).

RESULTS

There were 857 WWUD included in the study, contributing 9470 observations. Participants completed a median of nine (1st to 3rd quartile [Q1–Q3]: 3–19) follow-up visits and the median follow-up years were seven (Q1–Q3: 2.9–11.6). The loss to follow up rate was 5.55 per 100 person-years. At baseline, 596 (70%) women reported ever engaging in sex work in their lifetime; throughout the 13-year follow-up period, 476 (56%) women reported engaging in sex work at least once in the past six months. Table 1 summarizes the baseline participant characteristics. The median age was 38 years (Q1–Q3: 31–45), 46% identified as White, 54% identified as Black, Indigenous, or as a Person of Color, and 23% reported a minority sexual orientation. In the previous six months 88%, 68%, and 50% of women reported using stimulants, opioids, and/or alcohol at least once respectively. Over one-third of women were unhoused, and about three-quarters were living in the Downtown Eastside neighbourhood of Vancouver. In the previous six months, close to half of the participants reported some form of physical or sexual violence, 23% reported exposure to punitive policing practices, and 13% had been incarcerated.

Table 1.

Baseline characteristics of 857 women who use drugs in Vancouver, Canada, 2005–2018, data derived from the ACESS and VIDUS cohort studies

Characteristics Total n (%) Sex work at least once in the past 6-months n (%) Missingc n
(n= 857) Yes (n=327) No (n=530)
Age, median years (IQR)a 38 (31–45) 36 (30–43) 40 (33–46) 0
Race & Ethnicityb
White 398 (46%) 156 (48%) 238 (45%) 5
BIPOC 458 (54%) 170 (52%) 288 (55%)
Minority sexual orientationb 195 (23%) 88 (27%) 107 (20%) 1
Living in the DTESa 632 (74%) 274 (84%) 358 (68%) 0
Unhouseda 307 (36%) 141 (44%) 166 (32%) 6
Incarcerationa 110 (13%) 54 (17%) 56 (10%) 15
Punitive policinga 189 (23%) 94 (29%) 95 (19%) 17
Violencea 394 (46%) 150 (46%) 244 (46%) 0
HCVa 715 (84%) 271 (83%) 444 (84%) 4
HIVa 321 (39%) 113 (35%) 208 (39%) 0
Opioid usea 580 (68%) 267 (82%) 313 (59%) 3
Alcohol usea 423 (50%) 162 (53%) 254 (48%) 4
Stimulant usea 752 (88%) 312 (95%) 440 (83%) 1
Medications for opioid use disordera 421 (50%) 167 (52%) 254 (49%) 17
Supervised consumption site usea 432 (51%) 201 (62%) 231 (44%) 5
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Minority sexual orientation = identifying as gay, lesbian, bisexual, transexual, two-spirit, and/or queer.

Punitive Policing = being stopped, searched, detained, or assaulted by the police

Violence = being physically or sexually assaulted

Medications for opioid use disorder = being on buprenorphine, methadone, slow-release oral morphine, injectable opioid agonists, or naltrexone

Safe consumption site use = injected drugs at a supervised consumption/overdose prevention site

ACCESS: AIDS Care Cohort to Evaluate exposure to Survival Services; VIDUS: Vancouver Injection Drug Users Study; IQR: interquartile range; BIPOC: Black, Indigenous, other Person of Color; DTES: downtown eastside of Vancouver; HCV: hepatitis C virus; HIV: human immunodeficiency virus

a

Occurrences in the last six months.

b

Lifetime occurence.

c

There was less than 1% missing data in baseline variables.

Non-fatal overdose prevalence and trends over time

In total, 305 of 857 women (36%) reported overdosing at least once in the last six months during the 13-year study period. Throughout the study period, 206 of 476 (43%) women who engaged in sex work had at least one overdose event compared to 99 of 381 (26%) women who did not engage in sex work. Over time overdoses increased, with a marked increase starting in 2016 (Fig. 1).

Fig. 1.

Fig. 1.

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Prevalence of non-fatal overdose amongst 857 women who use drugs in Vancouver, Canada between 2005–2018, data derived from the ACCESS and VIDUS cohort studies

ACCESS: AIDS Care Cohort to Evaluate exposure to Survival Services; VIDUS: Vancouver Injection Drug Users Study.

Sex work association with non-fatal overdose

In the bivariate analyses (Table 2), variables significantly associated with an increased odds of overdose included the following social-structural factors: calendar year, minority sexual orientation, being unhoused, recent incarceration, exposure to punitive policing, utilization of supervised injection facilities, exposure to violence, and living in the Downtown East Side of Vancouver. Using MOUD was significantly associated with a reduced odds of overdose. Drug use behaviors and individual factors associated with overdose included alcohol, opioid, and stimulant use and age. In the final adjusted GEE model, sex work (Table 3) was not independently associated with an increased odds of overdose (AOR = 1.14, 95% CI: 0.93–1.40), after adjustment for key confounders (calendar year, minority sexual orientation, being unhoused, exposure to punitive policing, being on medications for opioid use disorder, using a supervised consumption site, exposure to violence, opioids use, stimulant use, and alcohol use).

Table 2.

Bivariate Logistic regression analyses using GEE examining associations between individual and structural factors and non-fatal overdose amongst 857 women who use drugs in Vancouver, Canada, 2005–2018, data derived from the ACESS and VIDUS cohort studies

Characteristics Odds ratio (95% CI)
Independent variable
 Sex worka 1.60 (1.31–1.95)
 Confounder variables
Temporal changes in drug supply
 Calendar Year 1.11 (1.08–1.14)
Public policy variables
 BIPOCb 1.22 (0.94–1.59)
 Minority sexual orientationb 1.51 (1.09–2.18)
 Unhouseda 1.70 (1.37–2.12)
 Incarcerationa 1.93 (1.45–2.59)
 Punitive Policinga 1.51 (1.09–2.18)
Community care access variables
 Medications for opioid use disordera 0.76 (0.62–0.94)
 Supervised consumption site usea 2.27 (1.84–2.80)
 Barriers to addiction carea 1.15 (0.80–1.65)
Social network variables
 Violencea 1.83 (1.51–2.22)
 Stable relationshipa 1.15 (0.95–1.38)
 Living in the DTESa 1.37 (1.11–1.69)
Drug use variables
 Opioid usea 3.63 (2.94–4.48)
 Stimulant usea 2.20 (1.69–2.88)
 Alcohol usea 1.93 (1.62–2.31)
Individual variables
 Agea 0.99 (0.98–1.01)
Open in a new tab

Minority sexual orientation = identifying as gay, lesbian, bisexual, transexual, two-spirit, and/or queer

Punitive Policing = being stopped, searched, detained, or assaulted by the police

Medications for opioid use disorder = being on buprenorphine, methadone, slow-release oral morphine, injectable opioid agonists, or naltrexone

Safe consumption site use = injected drugs at a supervised consumption/overdose prevention site Barriers to addiction care = being unable to access addiction treatment

Violence = being physically or sexually assaulted

Stable relationship = being legally married, or common law, or with a regular partner

ACCESS: AIDS Care Cohort to Evaluate exposure to Survival Services; VIDUS: Vancouver Injection

Drug Users Study; GEE: generalized estimating equations; CI: Confidence interval; BIPOC: Black, Indigenous, other Person of Color; DTES: downtown eastside of Vancouver

a

Time updated, occurrences in the last six months.

b

Fixed, from the baseline visit.

Table 3.

Multivariable GEE confounder model for the independent association between sex work and non-fatal overdose amongst 857 women who use drugs in Vancouver, Canada, 2005–2018, data derived from the ACESS and VIDUS cohort studies

Independent variable Adjusted odds ratio (95% CI)
Sex worka 1.14 (0.93–1.40)b
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a

Time updated, occurrences in the last six months.

b

Adjusted for calendar year, minority sexual orientation, being unhoused, exposure to punitive policing, being on medications for opioid use disorder, using a supervised consumption site, exposure to violence, opioids use, stimulant use, and alcohol use. Additional variables in the full multivariable model but which were not retained in the best fitting model included being unhoused, recent incarceration, and living in the Down Town East Side of Vancouver. All variables except for sexual orientation were measured occurrences in the last six months.

Exploratory analysis of individual and social-structural variables associated with overdose among women engaged in sex work

Table 4 summarizes individual and structural factors associated with overdose in the bivariate and multivariable analyses restricted to observations from the 476 WWUD in the cohort who engaged in sex work. In the multivariable model social-structural and induvial variables significantly associated with an increased odds overdose included calendar year (OR = 1.17, 95% CI: 1.12–1.23), reporting minority sexual orientation (OR = 1.43, 95% CI 1.00–2.03), exposure to punitive policing (OR = 1.97, 95% CI 1.30–2.96), exposure to violence (OR = 2.55, 95% CI: 1.88–3.46), opioid use (AOR = 3.02, 95% CI: 1.89–4.82), and alcohol use (OR = 1.66, 95% CI: 1.20–2.30). Using MOUD (OR = 0.49, 95% CI: 0.34–0.70) was significantly associated with a reduced odds of overdose in the multivariate model.

Table 4.

Exploratory logistic regression analysis using GEE of individual and structural factors associated with non-fatal overdose amongst 476 women who use drugs engaged in sex work in Vancouver, Canada 2005–2018, data derived from the ACESS and VIDUS cohort studies

Exploratory variables Bivariate odds ratio (95% CI) Multivariablec odds ratio (95% CI)
Temporal changes in drug supply
 Calendar Yeara 1.13 (1.08–1.19) 1.17 (1.12–1.23)
Public policy factors
 BIPOCb 1.20 (0.82–1.76)
 Minority sexual orientationb 1.46 (0.99–2.15) 1.43 (1.00–2.03)
 Unhouseda 1.47 (1.05–2.07) 1.39 (0.97–2.00)
 Incarcerationa 1.24 (0.62–2.47)
Punitive Policinga 1.58 (1.06–2.34) 1.97 (1.30–2.96)
Community care access variables
 Medications for opioid use disordera 0.54 (0.46–0.84) 0.49 (0.34–0.70)
 Supervised consumption site usea 1.54 (1.14–2.07)
 Barriers to addiction carea 1.31 (0.78–2.21)
Social network variables
 Violencea 2.16 (1.64–2.85) 2.55 (1.88–3.46)
 Stable relationshipa 1.24 (0.98–1.71)
 Living in the DTESa 0.85 (0.58–1.25)
Drug use variables
 Opioid usea 3.03 (2.00–4.60) 3.02 (1.89–4.82)
 Stimulant usea 1.53 (0.69–3.43)
 Alcohol usea 1.80 (1.34–2.42) 1.66 (1.20–2.30)
Individual variables
 Agea 1.00 (0.98–1.02)
Open in a new tab

Minority sexual orientation = identifying as gay, lesbian, bisexual, transexual, two-spirit, and/or queer

Punitive Policing = being stopped, searched, detained, or assaulted by the police

Medications for opioid use disorder = being on buprenorphine, methadone, slow-release oral morphine, injectable opioid agonists, or naltrexone

Safe consumption site use = injected drugs at a supervised consumption/overdose prevention site

Barriers to addiction care = being unable to access addiction treatment

Violence = being physically or sexually assaulted

Stable relationship = being legally married, or common law, or with a regular partner

ACCESS: AIDS Care Cohort to Evaluate exposure to Survival Services; VIDUS: Vancouver Injection

Drug Users Study; GEE: generalized estimating equations; CI: Confidence interval; BIPOC: Black, Indigenous, other Person of Color; DTES: downtown eastside of Vancouver

a

Time updated, occurrences in the last six months.

b

Fixed, from the baseline visit.

c

Single model that included all the variables listed under the multivariable odds ratio column. Additional variables in the full multivariable model but which were not retained in the best fitting model included supervised consumption site use.

DISCUSSION

In this study, we observed that sex work and overdose were prevalent among WWUD in Vancouver, Canada: 56% reported sex work engagement and 36% had at least one non-fatal overdose while enrolled in the study. Our study shows WWUD engaged in sex work had an increased overdose burden compared to WWUD who did not engage in sex work. Sex work was not significantly associated with overdose after adjusting for confounders, suggesting other social-structural and individual factors, rather than sex work itself, explained the elevated overdose burden. Though our exploratory results must be interpreted with caution given the inherit risk of exploratory analyses (Luijken et al., 2022), our findings are consistent with other overdose research suggesting that fentanyl in the drug supply, substance use, and treatment with MOUD were important factors associated with overdose. Our exploratory analysis also provides new insights into policing and violence factors that may be important social-structural drivers of overdose among WWUD engaged in sex work that merit further study and offer opportunities for overdose prevention (El-Bassel et al., 2020; Goldenberg et al., 2020)

Our exploratory results are consistent with other studies regarding the harms of the criminalization of both sex work and drug use for WWUD. A well-described consequence of the criminalization of drugs is the emergence of increasingly toxic substances into the unregulated supply (Ciccarone, 2017). We found that calendar year was associated with an increased odds of overdose among WWUD engaged in sex work and overdoses also increased over time in the cohort. This is in keeping with other research describing increasing toxicity of the drug supply in Vancouver during the same period (Ivsins et al., 2020; Tupper et al., 2018). In addition to policy action for the decriminalization of drug use, current safer supply programs under investigation in Vancouver should consider tailoring engagement efforts to WWUD given the known barriers to harm reduction and addiction treatment services women face (Bonn et al., 2020; Ivsins et al., 2020). Consistent with the other studies that find sex workers and WWUD disproportionately experience policing, almost a third of the women in our study were exposed to punitive policing practices and exposure to such practices was associated with a 1.97 times greater odds of overdose among WWUD engaged in sex work in our exploratory analysis (Deering et al., 2014; Goldenberg et al., 2020; Goldenberg et al., 2017). Among female sex workers in Kazakhstan, women who experienced high levels of punitive policing were more likely to use risky injection practices and have higher HIV and STI positivity (Mukherjee et al., 2022). Community-based risk reduction alternatives to policing and police training or diversion programs for sex work or drug possession could reduce police violence and related harms for WWUD (Footer et al., 2016; Reza-Paul et al., 2012; Riley et al., 2014). However, sex work decriminalization and policy reform would likely more substantively reduce policing among WWUD, highlighting the urgency for the advancement of sex worker’s rights during the present overdose crisis in Canada (Amnesty International, 2016; Socías et al., 2015).

In our exploratory analysis, aside from opioid use, exposure to violence presented the greatest association with overdose (OR 2.55) among WWUD engaged in sex work. Our results add to prior work that showed physical and intimate partner violence were strongly associated with overdose among sex workers who use drugs in Kazakhstan (El-Bassel et al., 2020). Such findings support theories on the bidirectional relationship between violence and drug use where violence causes pain and trauma increasing drug use and drug use increases a women’s vulnerability to violence via the disinhibiting effects of drug use among violence perpetrators (Stone & Rothman, 2019). Our works strengthen calls for interventions focused on the intersecting issues of violence, stigma, and sex work for WWUD that remain lacking in public health and programmatic responses to overdose prevention (Collins et al., 2019; Goldenberg, 2020). Tailored programming may be particularly needed for sexual orientation minority (gay, lesbian, bisexual, two-spirit, queer, or asexual) women. Our findings, consistent with others, suggest that such women may experience heightened intersecting levels of stigma and oppression and may have an increased risk of overdose (Hatzenbuehler & Pachankis, 2016; Moazen-Zadeh et al., 2019). While innovative programs like SisterSpace in Vancouver—a women’s only safe consumption space—offer a model of harm reduction that addresses social-structural factors (Boyd et al., 2020), efforts have not been scaled nor broadly integrated within addiction treatment services. Lessons learned from structural and multi-component approaches for HIV prevention among sex workers (Beattie et al., 2015; Reza-Paul et al., 2012; Ulibarri et al., 2019) offer models for integrating violence reduction interventions. These could include incorporating couples-based intimate partner interventions within office-based addiction treatment programs and/or establishing more women’s only MOUD treatment programs to increase access. Addressing violence in opioid use disorder treatment settings may reduce treatment barriers and increase MOUD retention among WWUD (El-Bassel et al., 2022). Interventions that increase access and engagement with MOUD are needed given the well-established benefits of MOUD (Gjersing & Bretteville-Jensen, 2014; Schiff et al., 2018) and our findings suggesting using MOUD was associated with a 51% reduced odds of overdose among WWUD engaged in sex work.

While there have long been calls for Housing First-based approaches for people who use drugs, our findings show a substantial proportion (38%) of study participants were unhoused at baseline (Aubry et al., 2015). Intimate partner violence and violence in low-income housing settings remain specific unanswered barriers to housing for WWUD (Collins et al., 2018; Knight et al., 2014; Lazarus et al., 2011). Given the high prevalence of homelessness and violence in our study, housing strategies for WWUD must include services for women experiencing violence and housing programs must ensure policies are in place to prevent further violence against women when housed (Collins et al., 2020; Yakubovich et al., 2022). Presently, emergency housing programs for women experiencing violence are typically segregated from addiction care and often actively exclude and discriminate against WWUD (Schumacher & Holt, 2012). A national US report from 2009 found that 71% of domestic violence shelter programs from 37 states did not admit women who were intoxicated, 46% discharged women who used substances, and only 26% offered any form of substance use treatment services (Schumacher & Holt, 2012). Welcoming and safe emergency shelter and housing options are needed to respond to the intersection of female gender, drug use, and sex work that presently exclude women from accessing the services they need most – housing, trauma care, harm reduction, and addiction treatment.

Strengths of this study include the use of a novel framework to examine sex work and social-structural factors associated with overdose and the use of longitudinal data from two large and long-running community-recruited cohort studies. However, several limitations should be noted. Failure to include women who died may result in survivor bias and prevents us for studying these associations with fatal overdose. The exploratory analysis examining factors associated with non-fatal overdose among WWUD engaged in sex work was designed to be hypothesis-generating, and the social structural variables associated with overdose we identified require further study. Additionally, our exploratory approach required multiple hypothesis testing risking multiplicity bias. Though we used a framework to broadly explore overdose risks, the ACCESS and VIDUS cohorts were not designed to focus on WWUD or people doing sex work. Therefore, there are undoubtedly additional unmeasured social structural confounders (Deering et al., 2014; El-Bassel & Strathdee, 2015) and some variables we did include, for example, calendar year as a proxy for the drug supply, lacked nuance. Future studies should examine drug checking data or toxicology data in overdose analyses. Additionally, our examination of race and ethnicity, sexual orientation, and gender identities lacked nuance. Further qualitative and quantitative research exploring the intersectional impact of gender, sexual orientation, and race identities on overdose among WWUD are needed. Similarly, our alcohol and drug use variables lacked granularity as we chose to use broad alcohol and drug use variables rather than more specific drug type or intensity use variables. Our aim was to focus social-structural factors associated with overdose rather than individual drug-use behaviours, however this is a limitation of our approach. Finally, non-random sampling recruitment techniques and the unique setting of Vancouver limits the generalizability of our findings to other WWUD globally.

In summary, in this study, WWUD engaged in sex work faced an increased overdose burden compared to WWUD not engaged in sex work; key social-structural factors associated with nonfatal overdose in this population included policing and violence. Findings are consistent with other research that demonstrates the deleterious consequences created by the criminalization of drug use and sex work and the resulting violence against women. Our findings highlight the need to investigate policies and interventions that address intersecting structural factors of sex work, violence, and policing as potential targets for effective overdose prevention among WWUD.

Supplementary Material

Supplementary Material

HIGHLIGHTS.

  • This study included 857 women who used drugs from Vancouver with 13 years of data.

  • During the study, 56% of women engaged in sex work and 36% had an overdose.

  • Women engaged in sex work experienced a disproportionate overdose burden.

  • Policing and gender-based violence, rather than sex work, may be key drivers of overdose.

  • Overdose prevention efforts that examine intersecting structural factors are needed.

Funding

The VIDUS and ACCESS cohorts were supported by the US National Institutes of Health (NIH) (U01DA038886, U01DA021525). Miriam Harris’s work was supported by the International Collaborative Addiction Medicine Research Fellowship (NIDA R25-DA037756). Seonaid Nolan is supported by the Michael Smith Foundation for Health Research and the University of British Columbia’s Steven Diamond Professorship in Addiction Care Innovation. Shira Goldenberg is partially supported by NIH (NIDA R01 DA028648). M-J Milloy is supported in part by the NIH (U01-DA0251525). He is the Canopy Growth professor of cannabis science at the University of British Columbia, a position established through arms’ length gifts to the university from Canopy Growth, a licensed producer of cannabis, and the Government of British Columbia’s Ministry of Mental health and addictions. Kanna Hayashi holds the St. Paul’s Hospital Chair in Substance Use Research and is supported in part by the NIH (U01DA038886), a Michael Smith Foundation for Health Research (MSFHR) Scholar Award, and the St. Paul’s Foundation. Nadia Fairbairn holds the Philip Owen Professorship in Addiction Medicine at UBC and is supported in part by the NIH (NIDA R25-DA037756), a Michael Smith Foundation for Health Research (MSFHR) Scholar Award, and the St. Paul’s Foundation.

Footnotes

Declarations of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Appendix 1. Supplementary materials

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