Shifts in substance use patterns among a cohort of people who use opioids after delisting of OxyContin in BC, Canada: An interrupted time series study

BACKGROUND

OxyContin was delisted from Canadian provincial drug formularies in March 2012 and replaced with a reformulated tamper-resistant form of oxycodone (i.e., OxyNeo). We assessed if delisting of OxyContin was associated with changes in the use of unregulated opioids and other substances among people who use opioids (PWUO).

METHODS

Data were derived from two prospective cohort studies of people who use drugs in Vancouver, BC, Canada from 2006 to 2018. PWUO who had at least one follow-up visit before and after delisting of OxyContin were included. Outcomes of interest were self-reported regular (i.e., at least weekly) use of heroin, non-prescribed prescription opioids, cannabis, methamphetamine, crack cocaine, and powder cocaine during the previous six months. Using quasi-experimental interrupted time series, we fit generalized least squares models to assess participants' immediate and long-term substance use practices after the policy change.

RESULTS

We analyzed data from 1014 participants who contributed to 17457 visits during the study. Following the delisting of OxyContin, heroin use increased immediately by 5.17% (95% confidence intervals [CI]: 0.68 to 9.67) and over time by 0.47% (0.35 to 0.58) per month. Non-prescribed prescription opioid use increased immediately by 1.80% (0.10 to 3.50) and over time by 0.16% (0.12 to 0.19) per month. Cannabis use increased immediately by 4.37% (0.88 to 7.87) and over time by 0.11% (0.02 to 0.19) per month. Methamphetamine use did not increase immediately but increased over time by 0.10% (0.01 to 0.18) per month. Crack cocaine use decreased immediately by 6.13% (-10.94 to -1.69) but not significantly over time. Lastly, powder cocaine use did not increase immediately or over time.

CONCLUSIONS

Delisting of OxyContin in BC was not associated with a reduction in unregulated opioid use among PWUO. Our findings point to a shift in substance use patterns of PWUO post-intervention and further highlight the unintended consequences of supply-reduction interventions in addressing the opioid epidemic.

Periods of Homelessness Linked to Higher VACS Index Among HIV-Positive People Who Use Drugs

We sought to evaluate the impact of homelessness on HIV disease progression among people who use unregulated drugs (PWUD) living with HIV and test if this association was mediated by adherence to antiretroviral therapy (ART). We applied general linear mixed-effects modeling to estimate the longitudinal relationship between homelessness and the Veterans Aging Cohort Study (VACS) Index, a validated measure of HIV disease progression that predicts all-cause mortality, among a prospective cohort of PWUD. In a longitudinal model adjusted for ART adherence, homelessness was significantly associated with increased VACS Index scores and 16% of the association was mediated by ART adherence. These findings indicate that homelessness was a significant risk factor for HIV disease progression and this association was marginally mediated by ART adherence. Future studies are needed to quantify the other mechanisms (e.g., food insecurity, mental health) by which homelessness increases mortality risk among PWUD living with HIV.

Initiation of opioid agonist treatment and subsequent substance use and other patterns among adolescents and young adults in Vancouver, Canada

BACKGROUND

Opioid agonist treatments (OAT) are effective interventions for reducing illicit opioid use; however, less is known about OAT among adolescents and young adults (AYA). This study sought to examine OAT retention and discontinuation among AYA.

METHODS

Data were derived from the At-Risk Youth Study, a prospective cohort of street-involved AYA in Vancouver, Canada, between September 2005 and December 2018. Multivariable Cox regression analysis was employed to identify sociodemographic, substance use, and other factors associated with time to first OAT. Substance use, homelessness, service utilization, and criminal justice patterns among AYA who did and did not initiate OAT were examined using before and after analysis.

RESULTS

Of 676 AYA who reported weekly illicit opioid use, 454 (67.2%) reported not being on OAT at some point over the study period and 217 (32.1%) initiated OAT over follow-up. In non-linear growth curve analysis, only participants retained in OAT demonstrated significant reductions in daily illicit opioid use when compared to 'no OAT' controls (p < 0.05). Nevertheless, reductions in homelessness (p = 0.070) and increases in difficulty accessing services (p = 0.078) were observed between participants retained in OAT vs. 'no OAT' controls, while reductions in homelessness (p = 0.085) and weekly non-medical prescription opioid use (NMPOU) (p = 0.061) were observed between 'OAT discontinuers' vs. 'no OAT' controls.

CONCLUSIONS

Despite finding that OAT retention was associated with significant reductions in daily illicit opioid use, no significant improvements in other key indicators were observed. This underscores the importance of providing supports alongside OAT to improve treatment outcomes among AYA.

MDMA-assisted therapy is associated with a reduction in chronic pain among people with post-traumatic stress disorder

INTRODUCTION

Increasing evidence demonstrates 3,4-methylenedioxymethamphetamine (MDMA)-assisted therapy (MDMA-AT) may be a safe and effective treatment for post-traumatic stress disorder (PTSD). There is growing interest in MDMA-AT to address a range of other health challenges. Chronic pain and PTSD are frequently comorbid, reciprocally interdependent conditions, though the possible role of MDMA-AT in treating chronic pain remains under-investigated. The present analysis examined the impact of manualized MDMA-AT on chronic pain severity among participants with PTSD who were enrolled in a Phase 2 clinical trial investigating MDMA-AT for PTSD (NCT03282123).

MATERIALS AND METHODS

Exploratory data from a subset of participants who completed chronic pain measures (n = 32) were drawn from a Phase 2 open-label study sponsored by the Multidisciplinary Association for Psychedelic Studies (MAPS). Multivariable analysis of variance (ANOVA) was utilized to compare pre- vs. post-treatment Chronic Pain Grade Scale (CPGS) values, adjusting for demographics (age, sex, and ethnicity). K-means clustering was then used to group the sample into three clusters to denote high (n = 9), medium (n = 11), and low (n = 12) baseline pain severity, and the same analysis was repeated for each cluster.

RESULTS

Among the 32 participants included in this analysis, 59% (n = 19) were women, 72% (n = 23) were white, and median age was 38 years [interquartile range (IQR) = 31-47]. Overall, 84% (n = 27) reported having pain, and 75% (n = 24) reported disability associated with their pain. Significant reductions in CPGS subscales for pain intensity and disability score, and overall CPGS severity grade were observed among participants in the highest pain cluster (n = 9, p < 0.05), and for pain intensity in the medium pain cluster (n = 11, p < 0.05) post- vs. pre-treatment.

DISCUSSION

Findings demonstrate a high prevalence of chronic pain in this sample of people with severe PTSD and that chronic pain scores among medium and high pain subgroups were significantly lower following MDMA-AT. While these data are preliminary, when considered alongside the frequency of comorbid chronic pain and PTSD and promising efficacy of MDMA-AT for treating PTSD, these findings encourage further research exploring the role of MDMA-AT for chronic pain.

Inability to access primary care clinics among people who inject drugs in a Canadian health care setting

OBJECTIVE

To examine the prevalence and correlation of self-reported inability to access community primary care clinics among people who inject drugs (PWID).

DESIGN

Self-report questionnaire data.

SETTING

Vancouver, BC.

PARTICIPANTS

Data were derived from 3 prospective cohort studies of PWID between 2013 and 2016.

MAIN OUTCOME MEASURES

Multivariable generalized estimating equations were used to determine prevalence of and reasons for self-reported inability to access primary care, as well as factors associated with inability to access care.

RESULTS

Of 1396 eligible participants, including 525 (37.6%) women, 209 (15.0%) persons were unable to access a primary care clinic at some point during the study period. In the multivariable analysis, factors independently associated with inability to access clinics included ever being diagnosed with a mental health disorder (adjusted odds ratio [AOR] = 1.63, 95% CI 1.14 to 2.35), dealing drugs (AOR = 1.60, 95% CI 1.15 to 2.22), using emergency services (AOR = 1.51, 95% CI 1.13 to 2.02), being female (AOR = 1.49, 95% CI 1.08 to 2.08), and testing positive for HIV (AOR = 0.47, 95% CI 0.30 to 0.72) (for all factors, P < .05).

CONCLUSION

Specific exposures were linked to challenges in accessing primary care among the sample of PWID, even in a publicly funded health care setting. Notably, models designed for care of people with HIV appear to increase access to primary care among PWID. Further research is needed to determine how to effectively treat accompanying mental illness, how to provide women-centred services, and how to connect people with primary care who would likely otherwise go to the emergency department.

Prevalence and longitudinal correlates of recent exposure to fentanyl among HIV-positive people who use unregulated drugs during a community-wide overdose crisis

The United States and Canada are experiencing an opioid overdose crisis driven largely by exposure to fentanyl (a potent synthetic opioid), with little known about fentanyl exposure among HIV-positive people who use unregulated drugs (PWUD). We sought to estimate the prevalence and correlates of fentanyl exposure among a community-recruited sample derived from a prospective cohort study of HIV-positive PWUD in Vancouver, Canada. Generalized linear mixed-effects analyses were used to identify longitudinal factors associated with a fentanyl-positive urine drug screen test. Between June 2016-November 2017, 456 participants were recruited and contributed 1007 observations. At baseline, 96% of participants were ART-exposed, 72% had an HIV viral load (VL) <50 copies/mL and 21% had a fentanyl-positive test. Longitudinally, fentanyl-positive tests were characterized by: younger participant age (Adjusted Odds Ratio [AOR] = 0.45), recent non-fatal overdose (AOR = 2.30), engagement in opioid agonist therapy (AOR = 1.91), and at least daily heroin injection (AOR = 11.27). CD4+ cell count was negatively associated with fentanyl urine positivity (AOR = 0.92) (all p < 0.05). We identified several risk factors for overdose linked to fentanyl exposure among this sample, although no link with HIV treatment engagement or detectable HIV VL. Innovative strategies are needed to reduce the harmful effects of the contaminated unregulated drug supply experienced by PWUD.

The Veterans Aging Cohort Study (VACS) Index Predicts Mortality in a Community-recruited Cohort of People With Human Immunodeficiency Virus (HIV) Who Use Illicit Drugs

The Veterans Aging Cohort Study (VACS) index combines commonly collected clinical biomarkers to estimate human immunodeficiency virus (HIV) disease severity. Among a prospective cohort of people living with HIV who use illicit drugs (PWUD) (n = 948), we found that the VACS index was significantly associated with mortality over a 20-year study period.

High-intensity cannabis use and hospitalization: a prospective cohort study of street-involved youth in Vancouver, Canada

BACKGROUND

There is concern that cannabis use negatively affects vulnerable groups such as youth; however, the relationship between cannabis use and health care utilization has not been well characterized in this population. We longitudinally evaluated the association between daily cannabis use and hospitalization among a prospective cohort of street-involved youth.

METHODS

Data were collected from the At-Risk Youth Study (ARYS) in Vancouver, Canada, from September 2005 to May 2015. Participants were interviewed semi-annually and multivariable generalized estimating equation (GEE) logistic regression was used to examine the relationship between daily cannabis use and hospitalization.

RESULTS

A total of 1216 participants (31.2% female) were included in this analysis, and 373 (30.7%) individuals reported hospitalization at some point during the study period. In a multivariable GEE analysis, daily cannabis use was not significantly associated with hospitalization (Adjusted Odds Ratio [AOR] = 1.17, 95% Confidence interval [CI] = 0.84, 1.65). We did observe a significant interaction between daily cannabis use and sex (AOR = 0.51, 95% CI = 0.34, 0.77), whereby cannabis use was associated with a decreased odds of hospitalization among males (AOR = 0.60, 95% CI = 0.47, 0.78), yet was not significantly associated with hospitalization among females (AOR = 1.19, 95% CI = 0.84, 1.67).

CONCLUSIONS

The finding that daily cannabis use was not associated with hospitalization among street-involved youth is encouraging given the high rates of cannabis use in this population and the expansion of cannabis legalization and regulation. Future studies, however, are warranted to monitor possible changes in the consequences of cannabis use as cannabis legalization and regulation increase internationally.

Pain and Barriers to Accessing Health Services Among People Who Use Drugs

BACKGROUND

The opioid overdose crisis underscores the need for health services among people who use drugs (PWUD) with concurrent pain.

AIMS

Investigating the effect of pain on barriers to accessing health services among PWUD.

DESIGN

Prospective cohort study.

SETTINGS

A setting of universal access to no-cost medical care in Vancouver, Canada from June 2014 to May 2016.

PARTICIPANTS/SUBJECTS

PWUD who completed at least one study interview.

METHODS

Data derived from interviewer-administered questionnaires were used for multivariable generalized linear mixed-effects multiple regression (GLMM) analyses.

RESULTS

Among 1,348 PWUD, 469 (34.8%) reported barriers to accessing health services at least once during the study period. The median average pain severity was 3 (IQR: 0-6) out of 10. A dose-response relationship was observed between greater pain and increased odds of reporting barriers to accessing health services (adjusted odds ratio [AOR]: 1.59, 95% confidence interval [CI]: 1.15-2.21, p = .005 for mild versus no pain; AOR: 1.76, 95% CI: 1.30-2.37, p < .001 for moderate versus no pain; AOR: 2.55, 95% CI: 1.92-3.37, p < .001 for severe versus no pain). Common barriers included poor treatment by health professionals, socio-structural barriers such as transportation or mobility, and long wait lists or wait times.

CONCLUSIONS

Pain may be a significant risk factor associated with increased barriers to accessing health services among PWUD. Attention to pain management may improve access to health services, and reducing barriers to health services may conversely improve pain management and its related risks and harms.

Withdrawal-associated injury site pain prevalence and correlates among opioid-using people who inject drugs in Vancouver, Canada

BACKGROUND

Pain can return temporarily to old injury sites during opioid withdrawal. The prevalence and impact of opioid withdrawal-associated injury site pain (WISP) in various groups is unknown.

METHODS

Using data from observational cohorts, we estimated the prevalence and correlates of WISP among opioid-using people who inject drugs (PWID). Between June and December 2015, data on WISP and opioid use behaviours were elicited from participants in three ongoing prospective cohort studies in Vancouver, Canada, who were aged 18 years and older and who self-reported at least daily injection of heroin or non-medical presciption opioids.

RESULTS

Among 631 individuals, 276 (43.7 %) had a healed injury (usually pain-free), among whom 112 (40.6 %) experienced WISP, representing 17.7 % of opioid-using PWID interviewed. In a multivariable logistic regression model, WISP was positively associated with having a high school diploma or above (Adjusted Odds Ratio [AOR] = 2.23, 95 % Confidence Interval [CI]: 1.31-3.84), any heroin use in the last six months (AOR = 2.00, 95 % CI: 1.14-3.57), feeling daily pain that required medication (AOR = 2.06, CI: 1.18-3.63), and negatively associated with older age at first drug use (AOR = 0.96, 95 % CI: 0.93-0.99). Among 112 individuals with WISP, 79 (70.5 %) said that having this pain affected their opioid use behaviour, of whom 57 (72.2 %) used more opioids, 19 (24.1 %) avoided opioid withdrawal, while 3 (3.8 %) no longer used opioids to avoid WISP.

CONCLUSIONS

WISP is prevalent among PWID with a previous injury, and may alter opioid use patterns. Improved care strategies for WISP are warrented.

Greater Pain Severity is Associated with Inability to Access Addiction Treatment Among a Cohort of People Who Use Drugs

Aim

Given that co-occurring pain is prevalent among people who use drugs (PWUD), we sought to explore the effect of pain severity on accessing addiction treatment.

Methods

Data were derived from two prospective cohort studies of PWUD in Vancouver, Canada from June 2014 to May 2016. Multivariable generalized linear mixed-effects multiple regression (GLMM) analyses were used to investigate the association between average pain severity and self-reported inability to access addiction treatment.

Results

Among 1348 PWUD, 136 (10.1%) reported being unable to access addiction treatment at least once over the study period. Individuals who reported being unable to access addiction treatment had a significantly higher median average pain severity score (median=5, IQR=0-7) compared to individuals reporting no inability to access addiction treatment (median=3, IQR=0-6, p=0.038). Greater pain severity was independently associated with higher odds of reporting inability to access addiction treatment (AOR: 1.75, 95%CI: 1.08-2.82 for mild-moderate vs no pain; AOR: 1.98, 95%CI: 1.27-3.09 for moderate-severe vs no pain).

Conclusion

PWUD with greater pain severity may be at higher risk of being unable to access addiction treatment, or vice versa. While further research is needed to confirm causal associations, these data suggest that there may be underlying pathways or mechanisms through which pain may be associated with access to addiction treatment for PWUD.

Characterising the increasing prevalence of crystal methamphetamine use in Vancouver, Canada, from 2006-2017: A gender-based analysis

INTRODUCTION

Methamphetamine use is increasing in North America and is associated with numerous negative health effects and social harms. As drug-related harms are often gendered, this study sought to examine the differential impacts of gender on the trends, risk factors and health implications of crystal methamphetamine use among a Canadian cohort of people with high rates of injection polysubstance use.

METHODS

Data were collected from two prospective cohorts of people who inject drugs in Vancouver, Canada. We examined trends in reported crystal methamphetamine use from 2006-2017 using the Cochrane-Armitage test for trend. We used multivariable generalised estimating equations, stratified by gender, to determine independent risk factors and health outcomes associated with crystal methamphetamine use.

RESULTS

In total, 1984 participants were included in the study, including 694 (35%) women. The prevalence of reported crystal methamphetamine use within the previous 6 months rose from 19% in 2006 to 36% in 2017, with a rise seen in both genders (P < 0.001). Reported crystal methamphetamine use was associated with numerous risk behaviours and drug-related harms in both genders, and in women it was associated with an increase in experiences of sexual violence (adjusted odds ratio 1.64, 95% confidence interval 1.18, 2.27).

CONCLUSIONS

These findings demonstrate the rising prevalence of reported crystal methamphetamine use in Vancouver in a cohort with high rates of polysubstance use. This work highlights drug and sex-related risk behaviours associated with crystal methamphetamine use for both genders, and underscores the need to develop strategies to address the growing use of crystal methamphetamine.

Effect of witnessing an overdose on the use of drug checking services among people who use illicit drugs in Vancouver, Canada

BACKGROUND

Since 2013, fentanyl-contaminated drugs have been driving North America's opioid-overdose epidemic. Drug checking, which enables people who use illicit drugs (PWUD) to test and receive feedback regarding the contents of their drugs, is being considered as a potential tool to address the toxic drug supply. While some PWUD witness overdoses, little is known about the impact of these experiences on subsequent risk reduction practices.

OBJECTIVE

The purpose of this study was to examine the effect of witnessing an overdose on drug checking service use.

METHODS

Data were derived from prospective cohorts of PWUD in Vancouver, Canada, a setting with a community-wide fentanyl overdose crisis, between June 1, 2018 and December 1, 2018. Multivariable logistic regression was used to estimate the effect of witnessing an overdose on drug checking service use.

RESULTS

1,426 participants were eligible for the study, including 530 females; 767 (53.8%) participants reported witnessing an overdose and 196 (13.7%) reported using drug checking services in the last 6 months. In multivariable analyses, after adjusting for a range of confounders including the use of fentanyl, witnessing an overdose was positively associated with drug checking service use (adjusted odds ratio = 2.32; 95% confidence interval: 1.57-3.49).

CONCLUSION

Our findings suggest that witnessing an overdose may motivate PWUD to use drug checking services. Given that only a small proportion of PWUD in the study reported using drug checking services, our findings highlight the need to continue to scale-up a range of overdose prevention interventions.

Overdose Risk and Acquiring Opioids for Nonmedical Use Exclusively from Physicians in Vancouver, Canada

BACKGROUND

A primary response to the alarming rise in overdose and mortality due to nonmedical prescription opioid (PO) use has been to restrict opioid prescribing; however, little is known about the relationship between obtaining opioids from a physician and overdose risk among people who use POs nonmedically and illicit street drugs. Objectives: Investigate the relationship between non-fatal overdose and acquiring POs exclusively from physicians for the purposes of engaging in nonmedical PO use. Methods: Data were collected between 2013 and 2016 among participants in two harmonized prospective cohort studies of people who use drugs in Vancouver: the At-Risk Youth Study (ARYS) and the Vancouver Injection Drug Users Study (VIDUS). Analyses were restricted to participants who engaged in nonmedical PO use and used generalized estimating equations. Results: Among 599 participants who used POs nonmedically, 82 (14%) individuals reported acquiring POs exclusively from a physician and 197 (33%) experienced a non-fatal overdose at some point over the study period. Acquiring POs exclusively from physicians was significantly and negatively associated with non-fatal overdose in the bivariate analysis (Odds Ratio = 0.60, 95% Confidence Interval (CI): 0.39-0.94) but not the final multivariate analysis (Adjusted Odds Ratio =0.87, 95% CI: 0.53-1.44). Conclusions: Compared to individuals who acquired POs from friends or the streets, participants who acquired POs exclusively from a physician were not at an increased risk of non-fatal overdose. Although responsible opioid prescribing is an important priority, additional strategies to address nonmedical PO use are urgently needed to reduce overdose and related morbidity and mortality.

Residential eviction predicts initiation of or relapse into crystal methamphetamine use among people who inject drugs: a prospective cohort study

Reports of increasing methamphetamine use among vulnerable populations may be attributed in part to the adaptive use of stimulants in response to the loss of stable housing through residential eviction. We employed multivariable recurrent event extended Cox regression to examine the independent association between recent evictions and initiation of or relapse into crystal methamphetamine use among people who inject drugs in Vancouver, Canada enrolled in two prospective cohort studies. In a multivariable analysis, eviction remained independently associated with methamphetamine initiation or relapse (adjusted hazard ratio = 1.90; 95% confidence interval: 1.31-2.75). Findings demonstrate the need to secure tenancies for drug-using populations to reduce harms.

Characterizing motivations for cannabis use in a cohort of people who use illicit drugs: A latent class analysis

Background

Cannabis use is common among marginalized people who use illicit drugs (PWUD) but reasons for use remain poorly investigated. We sought to explore how different intentions for cannabis use relate to social, structural, and behavioural factors among PWUD in Vancouver, Canada.

Methods

We used data from cannabis-using participants in two community-recruited prospective cohort studies of PWUD. Using latent class analysis, we identified discrete cannabis-using groups based on self-reported intentions for use. Generalized estimating equations were used to examine correlates of class membership.

Results

Between June 2016 and December 2018, 2,686 observations from 897 participants cannabis-using PWUD were analyzed. Four latent classes of cannabis use emerged: Class 1 (31.6%), characterized by non-medical purposes; Class 2 (37.5%), characterized by non-pain therapeutic use (e.g., stress, nausea/loss of appetite, and insomnia); characterized by Class 3 (21.9%) predominantly pain relief; and Class 4 (9.0%), characterized by a wide range of therapeutic uses in addition to pain management, including insomnia, stress, nausea/loss of appetite, and harm reduction. Class-specific structural, substance-, and health-related differences were observed, including indicators of better physical and mental health among the “recreational” class, despite evidence of more structural vulnerabilities (e.g., homelessness, incarceration).

Conclusions

Our findings demonstrate a wide spectrum of motivations for cannabis use among PWUD. We observed important health-related differences between latent classes, demonstrating possible unmet healthcare needs among PWUD reporting therapeutic cannabis use. These findings inform ongoing policy surrounding access to cannabis for harm reduction purposes and applications of medical cannabis for PWUD.

Temporal changes in non-fatal opioid overdose patterns among people who use drugs in a Canadian setting

Background and Aims: Little is known about how the expansion of opioid agonist therapy (OAT) and emergence of fentanyl in the illicit drug supply in North America has influenced non-fatal opioid overdose (NFOD) risk. Therefore, we sought to identify patterns of substance use and addiction treatment engagement (i.e., OAT, other inpatient or outpatient treatment) prior to NFOD, as well as the trends and correlates of each pattern among people who use drugs (PWUD) in Vancouver, Canada. Methods: Data were derived from participants in three prospective cohorts of PWUD in Vancouver in 2009-2016. Observations from participants reporting opioid-related NFOD in the previous six months were included. A latent class analysis was used to identify classes based on substances used at the time of last NFOD and addiction treatment engagement in the month prior to the last NFOD. Multivariable generalized estimating equations estimated the correlates of each class membership. Results: In total, 889 observations from 570 participants were included. Four distinct classes were identified: (1) polysubstance use (PSU) and addiction treatment engagement; (2) PSU without treatment engagement; (3) exposure to unknown substances, mostly without treatment engagement; and (4) primary heroin users without treatment engagement. The class of exposure to unknown substances appeared in 2015 and became the dominant group (76.9%) in 2016. In multivariable analyses, the odds of membership in the class of primary heroin users decreased over time (adjusted odds ratio [AOR]: 0.74, 95% confidence interval [CI]: 0.68-0.81). Conclusions: Changing profiles of PWUD reporting opioid-related NFOD were seen over time. Notably, there was a sudden increase in reports of overdose following exposure to unknown substances since 2015, the majority of whom reported no recent addiction treatment engagement. Further study into patterns of substance use and strategies to improve addiction treatment engagement is needed to improve and focus overdose prevention efforts.

The effect of injecting alone on the use of drug checking services among people who inject drugs

OBJECTIVES

Drug checking services aim to provide people who use drugs with information on the content and purity of their substances as a harm reduction intervention. The objective of this study was to determine the relationship between injecting alone and use of drug checking services in Vancouver, Canada.

METHODS

Data were derived from three prospective cohort studies of people who inject drugs (PWID). We conducted bivariable and multivariable logistic regression analysis to estimate the effect of injecting alone on use of drug checking services.

RESULTS

Between May 2018 and December 2018, a total of 793 people who inject drugs were included in the study: 579 (73.0%) reported injecting alone and 177 (22.3%) reported use of drug checking services. In a multivariable model adjusted for various confounders (including various sociodemographic variables, drug use patterns, and whether participants had suffered physical attacks/violence), injecting alone was negatively associated with use of drug checking services (Adjusted Odds Ratio = 0.65; 95% Confidence Interval: 0.44-0.97).

CONCLUSIONS

We observed a negative association between injecting drugs alone and use of drug checking services, which may be due in part to a number of exogenous factors that prevent people who inject alone from accessing drug checking services (e.g., stigma, location of services). As these individuals are at heightened risk of experiencing overdoses, there is a need to pursue other strategies to reach this group of people who use drugs.

Coercion into addiction treatment and subsequent substance use patterns among people who use illicit drugs in Vancouver, Canada

BACKGROUND AND AIMS

Many people who use drugs (PWUD) are coerced into receiving treatment. This study aimed to assess changes in substance use and related outcomes before versus after treatment in people coerced into treatment, voluntarily attending treatment or not attending treatment.

DESIGN

Data from three linked prospective cohort studies of PWUD were used. McNemar's test and non-linear growth curve modeling were employed to: (a) assess changes in substance use patterns before and after coerced addiction treatment and (b) compare these changes with changes in PWUD who (1) voluntarily accessed and (2) did not access treatment.

SETTING

Vancouver, Canada.

PARTICIPANTS

A total of 3196 community-recruited PWUD.

MEASUREMENTS

The outcome variables were substance use and related outcomes assessed by self-reported questionnaire. The input variable was self-reported coerced addiction treatment (defined as being forced into addiction treatment by a doctor or the criminal justice system), voluntary treatment versus no treatment.

FINDINGS

Between September 2005 and June 2015, 399 (12.5%) participants reported being coerced into addiction treatment. In McNemar's test, there were no statistically significant reductions in within-group substance use outcomes for people coerced into treatment, voluntarily attending treatment or not attending treatment. In non-linear growth curve analyses, there were no statistically significant differences in the before and after substance use patterns between those coerced into treatment versus either of the two control groups (all P > 0.05). In subanalyses, we found no statistically significant differences in substance use patterns between people who reported formal coerced treatment through the criminal justice system and people who reported informal coerced treatment through a physician.

CONCLUSIONS

Among PWUD in Vancouver, Canada, there appear to be no statistically significant improvements in substance use outcomes among those reporting coerced addiction treatment, those voluntarily accessing treatment, and those not attending treatment.

Initiation into heroin use among street-involved youth in a Canadian setting: A longitudinal cohort study

BACKGROUND

Emerging evidence suggests that non-medical prescription opioid (NMPO) use may be a risk factor for initiating heroin use; however, pathways from PO to heroin use among youth remain underexplored. We sought to examine the association between NMPO use and heroin initiation.

METHODS

Between September 2005 and June 2017 data were derived from an open prospective cohort of street-involved youth aged 14-28 who use illegal drugs in Vancouver, Canada. The study included 526 youth who had never used non-injection heroin, and 652 youth who had never used injection heroin at baseline. We used Cox proportional hazards regressions to examine the association between NMPO use - in addition to other substance use patterns - and subsequent initiation into non-injection and injection heroin use.

RESULTS

Among those who had never used non-injection heroin at baseline, 133 (25.3%) initiated non-injection heroin use during the study period. Among those who had never injected heroin at baseline, 137 (21.0%) initiated heroin injection during the study period. In multivariable analyses, NMPO use, crack use, and crystal methamphetamine use predicted non-injection heroin initiation (all p < 0.05). In separate multivariable analyses, non-injection heroin and crystal methamphetamine predicted heroin injection initiation (all p < 0.05).

CONCLUSIONS

Among street-involved youth in this setting, NMPO use predicted initiation into non-injection heroin use but not initiation into heroin injection. Interestingly, crack cocaine and crystal methamphetamine use were stronger predictors of heroin initiation than NMPO use was, suggesting that stimulant use may carry greater risks for heroin initiation than NMPO use.

A gender-based analysis of nonmedical prescription opioid use among people who use illicit drugs

BACKGROUND

Research investigating the unique impacts associated with engaging in nonmedical prescription opioid use (NMPOU) among males and females who also use illicit drugs is needed.

METHODS

Data were collected between 2013 and 2017 from two linked prospective cohort studies in Vancouver: the At-Risk Youth Study and Vancouver Injection Drug Users Study. Generalized estimating equations were used to identify factors associated with engaging in NMPOU among females and males separately.

RESULTS

Among 1459 participants, 534 were female (37%). Similar proportions of females (46%) and males (48%) engaged in NMPOU at their first visit during the study period. In multivariable analyses, factors associated with NMPOU among both males and females included heroin use, overdose, drug dealing, and difficulty accessing health and social services. Among females, those who engaged in NMPOU were more likely to report Caucasian or white ethnicity, cocaine use, crystal methamphetamine use, and sex work; among males, those who engaged in NMPOU were older, reported crack use and engaged in binge drug use (all p < 0.05).

CONCLUSION

The prevalence of NMPOU was similar among males and females who use illicit drugs in Vancouver, and NMPOU was independently associated with markers of vulnerability among both genders. Findings highlight the need for a comprehensive public health approach to address NMPOU that integrates overdose prevention and reversal services, employment opportunities, and better access to services for both women and men.

The relationship between childhood emotional abuse and chronic pain among people who inject drugs in Vancouver, Canada

BACKGROUND

People who inject drugs (PWID) often contend with chronic pain as a result of illness and trauma, and such pain is known to have significant impacts on mental health, quality of life, and substance use behaviours. Although PWID are also known to have high rates of childhood trauma, little is known about how childhood emotional abuse may be associated with chronic pain in this population.

OBJECTIVE

We undertook this study to explore emotional abuse and chronic pain among PWID.

PARTICIPANTS AND SETTING

This study comprised a total of 1459 participants in Vancouver, Canada between June 2014 and November 2016.

METHODS

We employed multivariable generalized estimating equations with data derived from two prospective cohort studies of community-recruited PWID to examine the relationship between childhood emotional abuse and chronic pain in the past six months.

RESULTS

Among eligible participants, 591 (40.5%) reported childhood emotional abuse, and 760 (52.1%) reported chronic pain in the previous six months. In a multivariable analysis, experiencing childhood emotional abuse remained independently associated with chronic pain (adjusted odds ratio: 1.25; 95% confidence interval: 1.01-1.53) after adjustment for a range of socio-demographic and drug use confounders.

CONCLUSIONS

Our findings suggest that childhood emotional abuse may have lasting relationships with chronic pain among PWID, potentially through established physiological and psychological mechanisms. Current chronic pain treatment may benefit from the evaluation of life course vulnerabilities that may be amenable to earlier interventions. Further, increased availability of effective trauma-informed chronic pain treatment is needed among this vulnerable population.

Knowledge of Fentanyl and Perceived Risk of Overdose Among Persons Who Use Drugs in Vancouver, Canada

OBJECTIVES

In North America, the illicit drug supply is increasingly contaminated by illicitly manufactured fentanyl. We sought to assess the level and source of fentanyl risk knowledge, defined as knowledge of the overdose risks associated with fentanyl, and characterize the prevalence and correlates of perceived risk of personally having a fentanyl overdose among persons who use illicit drugs (PWUD) in Vancouver, British Columbia.

METHODS

We derived data from 3 prospective cohorts of PWUD in Vancouver from December 2016 through May 2017. We used multivariable ordinal regression analysis to identify factors associated with a lower perceived risk of having a fentanyl overdose.

RESULTS

Of 1166 participants, 1095 (93.9%) had fentanyl risk knowledge. Of 1137 participants who answered questions about their perceived risk of having a fentanyl overdose, 398 (35.0%) perceived having no risk, 426 (37.5%) perceived having low risk, and 313 (27.5%) perceived having moderate or high risk. Never or rarely using opioids (n = 541, 65.7%) was the most common reason for reporting no or low perceived risk (n = 824), whereas 137 (16.6%) participants reported daily heroin use. In multivariable analysis, compared with participants who perceived a moderate or high risk, participants who perceived a lower risk were less likely to report a recent nonfatal overdose (adjusted odds ratio [aOR] = 0.28; P < .001), recent injection drug use (aOR = 0.34; P < .001), and awareness of recent exposure to fentanyl (aOR = 0.34; P < .001).

CONCLUSION

Despite a high level of fentanyl risk knowledge, most study participants did not translate this knowledge into a risk of having an overdose. Although participants who perceived a lower risk were less likely to have had an overdose, a considerable proportion was engaged in daily opioid use, suggesting the need to improve overdose prevention efforts.

Homelessness and incarceration associated with relapse into stimulant and opioid use among youth who are street-involved in Vancouver, Canada

INTRODUCTION AND AIMS

While much research has sought to identify the factors associated with initiation and cessation of various forms of drug use among vulnerable youth, little is known about relapse into drug use in this population. We sought to characterise relapse into stimulant and opioid use among street-involved youth in Vancouver, Canada.

DESIGN AND METHODS

Data were collected between 2005 and 2017 from the At-Risk Youth Study, a prospective cohort study of street-involved youth who use illicit drugs in Vancouver. Multivariable extended Cox regression was utilised to identify factors associated with relapse into illegal stimulants and/or opioids among youth who had previously ceased using stimulants and/or opioids for 6 months or longer.

RESULTS

Among 246 participants who reported a period of cessation lasting 6 months or longer, 165 (67.1%) relapsed at some point during study follow-up. Youth who were recently incarcerated (adjusted hazard ratio [AHR]: 1.46), homeless (AHR: 1.43), or had a history of daily stimulant use (AHR: 1.48) were significantly more likely to report relapse, while youth of who identified as white (AHR: 0.74) were significantly less likely to report relapse (all P < 0.05).

DISCUSSION AND CONCLUSIONS

Relapse into stimulants and/or opioids was common among youth in our setting, and incarceration, homelessness, and daily stimulant use were found to be positively associated with relapse among youth. Findings suggest that increased access to youth housing supports and alternatives to the criminalisation of drug use may help to reduce the rates of relapse into stimulants and/or opioids in this population.

The relationship between parental heavy drinking and non-fatal overdose among people who inject drugs in Vancouver, Canada

BACKGROUND

Despite the acute drug-related and behavioural risk factors for experiencing a drug overdose, few remote childhood experiences have been examined as risk factors for subsequent later life overdose risk. Parental heavy drinking has been associated with some later life negative outcomes, but little is known regarding the impact on drug overdoses, especially among people who inject drugs. Given the current overdose crisis in North America, we sought to evaluate the impact of parental heavy drinking on later life non-fatal overdose among people who inject drugs in Vancouver, Canada.

METHODS

Data were derived from two prospective cohort studies of community-recruited people who inject drugs in Vancouver between December 2012 and May 2016. We employed multivariable generalized estimating equations to examine the relationship between parental heavy drinking and non-fatal overdose in the past six months.

RESULTS

Among 327 eligible participants, 111 (33.9%) reported parental heavy drinking and 95 (29.1%) reported a non-fatal overdose at least once during the study period. In a multivariable analysis, experiencing parental heavy drinking remained independently associated with non-fatal overdose (adjusted odds ratio: 1.69; 95% confidence interval: 1.07-2.66) after adjustment for a range of socio-demographic and drug using confounders.

CONCLUSIONS

These findings suggest long-term negative impacts of parental heavy drinking, on subsequent risk taking or other mechanisms associated with overdose. Current overdose prevention efforts may benefit from the evaluation of life course vulnerabilities that may be amenable to earlier interventions.

High Prevalence of Self-Reported Exposure to Adulterated Drugs Among People Who Experienced an Opioid Overdose in Canada: A Cohort Study

BACKGROUND

In North America, rates of overdoses are increasing largely due to the adulteration of illicit drugs by illicit synthetic opioids.

OBJECTIVES

We sought to examine the prevalence and correlates of self-reported exposure to adulterated drugs among people who experienced a non-fatal opioid overdose.

METHODS

Data were derived from three prospective cohort studies of people who use drugs in Vancouver, Canada between June and November 2016. Multivariable logistic regression analyses were used to examine the prevalence and correlates of self-reported exposure to adulterated drugs.

RESULTS

Among 117 participants who reported symptoms consistent with a non-fatal opioid overdose, 78 (66.7%) reported believing the drug was adulterated during their last overdose. Of those, 42 (53.8%) had not perceived adulteration prior to overdose. In the multivariable analysis, engagement in opioid agonist therapy (Adjusted Odds Ratio [AOR] = 2.79, 95% Confidence Interval [CI]: 1.10, 7.45) was independently associated with having not perceived adulteration prior to overdose. Daily heroin use (AOR = 5.28; 95% CI: 1.92, 15.97) and reporting supervised injection site staff were present at most recent overdose (AOR = 6.16; 95% CI: 1.25, 47.27) were independently associated with having perceived adulteration prior to overdose. Conclusions/Importance: We found a high prevalence of believing adulterated drugs were present for the most recent overdose. Further, the high prevalence of unperceived adulteration prior to overdose supports the need to lower the risk of overdose by providing individuals with options to consume drugs in a safer manner, including supervised consumption sites.

Perceived Devaluation among a Cohort of Street-Involved Youth in Vancouver, Canada

BACKGROUND

Perceived devaluation is a barrier to seeking mental and physical health services among people who use illicit drugs.

OBJECTIVE

Assessing the prevalence and correlates of perceived devaluation within a cohort of street-involved youth.

METHODS

Data were drawn from an open prospective cohort of street-involved youth who use illicit drugs (aged 14-26 at study enrollment) between December 2013 and May 2015 in Vancouver, Canada. Perceived devaluation was measured using an adapted version of Perceived Devaluation and Discrimination scale. Multivariable generalized estimating equations were constructed to examine factors independently associated with high perceived devaluation.

RESULTS

Among 411 street-involved youth, 95.1% reported high perceived devaluation at some point during the study period. In a multivariable analysis, youth who reported high perceived devaluation were significantly more likely to engage in: unprotected sex (Adjusted Odds Ratio [AOR] = 1.56, 95% Confidence Interval 1.03-2.37); heavy alcohol use (AOR = 2.31, 95% CI 1.22-4.36); and daily heroin use (AOR = 2.07, 95% CI 1.16-3.70). Youth who resided in the Downtown Eastside neighborhood were significantly less likely to report high perceived devaluation (AOR = 0.41, 95% CI 0.26-0.65).

CONCLUSIONS

Perceived devaluation was extremely prevalent among street-involved youth in our sample. We also observed that youth most in need of health and social services were significantly more likely to report high levels of perceived devaluation which may result in a reluctance to seek out key services and supports. These findings highlight the need to implement stigma reduction interventions for vulnerable youth in this setting.

HIV Incidence Among Men Who Have Sex with Men and Inject Drugs in a Canadian Setting

Few data on HIV incidence among men who have sex with men and inject drugs (MSM-PWID) are available. Drawing on a prospective cohort in Vancouver, Canada, we examined the relationship between MSM status and HIV incidence among PWID using Kaplan-Meier analyses and extended Cox regression. Data were collected from 1996 to 2014 and analyzed in 2017. Of 1131 HIV-negative male PWID, 8.6% (n = 97) reported sex with men over the study period. MSM status was crudely associated with HIV incidence [Hazard Ratio (HR) = 1.81; 95% CI 1.08-3.03], but not after adjustment for daily cocaine injection and syringe borrowing (Adjusted HR = 1.33; 95% CI 0.78-2.28). Findings highlight the need for harm reduction interventions and socio-behavioral research focused on MSM-PWID.

An age-based analysis of nonmedical prescription opioid use among people who use illegal drugs in Vancouver, Canada

BACKGROUND

Nonmedical prescription opioid use (NMPOU) is a serious public health problem in North America. At a population-level, previous research has identified differences in the prevalence and correlates of NMPOU among younger versus older age groups; however, less is known about age-related differences in NMPOU among people who use illegal drugs.

METHODS

Data were collected between 2013 and 2015 from two linked prospective cohort studies in Vancouver, Canada: the At-Risk Youth Study (ARYS) and the Vancouver Injection Drug Users Study (VIDUS). Factors independently associated with NMPOU among younger (ARYS) and older (VIDUS) participants were examined separately using bivariate and multivariate generalized estimating equations.

RESULTS

A total of 1162 participants were included. Among 405 eligible younger participants (Median age = 25; Inter-Quartile Range [IQR]: 22-28), 40% (n = 160) reported engaging in NMPOU at baseline; among 757 older participants (Median age = 48, IQR: 40-55), 35% (n = 262) reported engaging in NMPOU at baseline. In separate multivariate analyses of younger and older participants, NMPOU was positively and independently associated with heroin use (younger: Adjusted Odds Ratio [AOR] = 3.12, 95% Confidence Interval [CI]: 2.08-4.68; older: AOR = 2.79, 95% CI: 2.08-3.74), drug dealing (younger: AOR = 2.22, 95% CI: 1.58-3.13; older: AOR = 1.87, 95% CI: 1.40-2.49), and difficulty accessing services (younger: AOR = 1.47, 95% CI: 1.04-2.09; older: AOR = 1.74, 95% CI: 1.32-2.29). Among the youth cohort only, NMPOU was associated with younger age (AOR = 1.12, 95% CI: 1.05-1.19), crack use (AOR = 1.56, 95% CI: 1.06-2.30), and binge drug use (AOR = 1.41, 95% CI: 1.00-1.97); older participants who engaged in NMPOU were more likely to report crystal methamphetamine use (AOR = 1.97, 95% CI: 1.46-2.66), non-fatal overdose (AOR = 1.76, 95% CI: 1.20-2.60) and sex work (AOR = 1.49, 95% CI: 1.00-2.22).

DISCUSSION

The prevalence of NMPOU is similar among younger and older people who use drugs, and independently associated with markers of vulnerability among both age groups. Adults who engage in NMPOU are at risk for non-fatal overdose, which highlights the need for youth and adult-specific strategies to address NMPOU that include better access to health and social services, as well as a range of addiction treatment options for opioid use. Findings also underscore the importance of improving pain treatment strategies tailored for PWUD.

3,4-Methylenedioxymethamphetamine (MDMA; ecstasy) use and transitions to injection drug use among street-involved youth

Background: Despite the popularity of 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) among young people across North America and Europe, MDMA is rarely explored in studies of young people at high risk of injecting drugs. We conducted a study among street-involved youth who use illicit drugs in Vancouver, Canada, to understand if use of MDMA is associated with initiation of injection drugs. Methods: We followed injection-naïve participants in the At-Risk Youth Study (ARYS), an ongoing prospective cohort of street-involved youth aged 14-26 who use illicit drugs. Bivariate and multivariate extended Cox models with time-updated variables were used to examine the association between MDMA use and initiation of injection drug use between September 2005 and May 2015. Results: Among 483 youth, 306 (63.4%) had a history of MDMA use and 218 (45.1%) had used MDMA in the previous 6 months at baseline. A total of 105 (21.7%) youth initiated injection drug use over the 10-year period, yielding an incidence density of 8.51 (95% confidence interval [CI]: 6.96-10.30) per 100 person-years. MDMA use was not significantly associated with initiating injection drugs at the bivariate (hazard ratio: 0.93, 95% CI: 0.61-1.42) or multivariate (adjusted hazard ratio: 0.88, 95% CI: 0.57-1.35) level, after adjusting for socio-demographic and substance use confounders. Conclusions: Amid ongoing frequent use of MDMA among some young people in North America, we did not observe an elevated risk of injection initiation among those who used MDMA in this cohort of street-involved youth.

Regular MDMA use is associated with decreased risk of drug injection among street-involved youth who use illicit drugs

OBJECTIVES

Childhood trauma is common among street-involved youth and is associated with injection drug use. Illicit 3,4-Methylenedioxymethamphetamine (MDMA) use is also common among street-involved youth, and data suggest this substance has clinical utility in management of post-traumatic stress disorder (PTSD) and associated harms. Despite this, little is known about co-occurring patterns of MDMA use and injection drug use.

METHODS

Data were derived from a prospective cohort of street-involved youth using illicit drugs in Vancouver, Canada. Using multivariable generalized estimating equation logistic regression, we examined the association between MDMA use and the use of injection drugs, adjusting for confounders such as polysubstance use and sociodemographic factors.

RESULTS

4941 surveys from 1208 participants between September 2005 and May 2015 were included. Of these, 829 (68.6%) were male, 815 (67.5%) reported white ethnicity, and median age was 21.7 years. Overall, 599 (49.6%) participants reported MDMA use, 544 (45.0%) reported injection drug use, and 244 (20.2%) reported concurrent MDMA and injection drug use at least once during the study period. In multivariable analyses, regular MDMA use was significantly negatively associated with injection drug use (Adjusted Odds Ratio [AOR] = 0.57, 95% CI: 0.46-0.69).

DISCUSSION

After accounting for socio-demographic factors and polysubstance use, periods of reported regular MDMA use were negatively associated with reported injection drug use among this cohort. These findings suggest that, unlike the use of most other non-injection drugs, illicit MDMA use does not appear to promote injection drug use but rather is associated with a reduced likelihood of injection drug use.

Hepatitis C cascade of care among people who inject drugs in Vancouver, Canada

BACKGROUND

People who inject drugs (PWID) have high rates of hepatitis C virus (HCV) infection. Little is known about the rates of diagnosis and treatment for HCV among PWID. Therefore, this study aims to characterize the cascade of care in Vancouver, Canada, to improve HCV treatment access and delivery for PWID.

METHODS

Data were derived from 3 prospective cohort studies of PWID in Vancouver, Canada, between December 2005 and May 2015. The progression of participants was identified through 5 steps in the cascade of care: (1) chronic HCV; (2) linkage to HCV care; (3) liver disease assessment; (4) initiation of treatment; and (5) completion of treatment. Predictors of undergoing liver disease assessment for HCV treatment were identified using a multivariable extended Cox regression model.

RESULTS

Among 1571 participants with chronic HCV, 1359 (86.5%) had ever been linked to care, 1257 (80.0%) had undergone liver disease assessment, 163 (10.4%) had ever started HCV treatment, and 71 (4.5%) had ever completed treatment. In multivariable analyses, human immunodeficiency virus (HIV) seropositivity, use of methadone maintenance therapy, and hospitalization in the past 6 months were independently and positively associated with undergoing liver disease assessment (all P < .001), whereas daily heroin injection was independently and negatively associated with undergoing liver disease assessment (P < .001).

CONCLUSIONS

Among this cohort of PWID, few had been started on or completed treatment for HCV. These findings highlight the need to improve the prescribing of HCV treatment among PWID with active substance use.

Factors associated with methadone maintenance therapy discontinuation among people who inject drugs

BACKGROUND

Methadone maintenance therapy (MMT) continues to be a key treatment for opioid use disorder, although premature discontinuation of MMT can increase risk for overdose and other severe harms. We examined sociodemographic characteristics, substance use patterns and social-structural exposures associated with MMT discontinuation among a cohort of people who use drugs (PWUD) in Vancouver, Canada.

METHODS

Data were derived from VIDUS and ACCESS, prospective cohorts of PWUD in Vancouver, Canada. The outcome of interest was self-reported discontinuation of MMT within the last six months. Multivariable Generalized Estimating Equations (GEE) were conducted to identify factors independently associated with MMT discontinuation.

RESULTS

Between 2005 and 2015, 1301 PWUD who had accessed MMT were recruited, among whom 288 (22.1%) discontinued MMT at least once during the study period. In multivariable GEE analyses, homelessness (Adjusted Odds Ratio [AOR] = 1.46, 95% Confidence Interval [95% CI]: 1.09-1.95), daily heroin injection (AOR = 5.17, 95% CI: 3.82-6.99), daily prescription opioid use (injection or non-injection) (AOR = 2.18, 95% CI: 1.30-3.67), recent incarceration (AOR = 1.46, 95% CI: 1.01-2.12), and not being on any form of income assistance (AOR = 2.14, 95% CI: 1.33-3.46) were each independently positively associated with MMT discontinuation. Participants with more study visits on methadone (>50% vs. ≤50% of visits) (AOR = 0.63, 95% CI: 0.47-0.85) and those with higher methadone dose (>100 mg vs. <60 mg per day) (AOR = 0.44, 95% CI: 0.31-0.62) were less likely to discontinue MMT.

DISCUSSION AND CONCLUSIONS

Discontinuation of MMT in this urban setting was associated with recent homelessness and incarceration, not accessing social income assistance, as well as daily prescription opioid use and daily heroin injection drug use. These findings underscore a need to reduce potential barriers to MMT retention by providing access to stable housing and preventing treatment interruptions during transitions between community and custodial settings.

Use of withdrawal management services among people who use illicit drugs in Vancouver, Canada

Background

For many individuals with substance use disorders, the entry point for addiction treatment can be through withdrawal management (e.g. detoxification) services. However, little is known about the factors that predict withdrawal management service use among people who use illicit drugs (PWUD). Using data derived from two prospective cohorts of PWUD, we conducted a longitudinal data analysis of factors associated with use of withdrawal management services.

Methods

Individuals participating in two cohorts of PWUD were prospectively followed between December 2005 and May 2016 in Vancouver, Canada. Bivariate and multivariate generalized estimating equations were used to examine factors associated with use of withdrawal management services.

Results

Out of a total of 2001 participants, 339 (16.9%) individuals reported having been to a withdrawal management centre in the previous 6 months at some point during the study period. In multivariate analyses, male sex (adjusted odds ratio [AOR]: 1.62, 95% Confidence Interval [CI]: 1.17–2.24), homelessness (AOR: 1.86, 95% CI: 1.45–2.38), binge use of any substance (AOR: 1.34, 95% CI: 1.08–1.67), having attended a supervised injection facility (AOR: 1.66, 95% CI: 1.3–2.11), and having accessed other addiction medicine treatment or supports (other than withdrawal management services or opioid agonist therapy; AOR: 3.34, 95% CI: 2.64–4.22) were positively associated with having accessed withdrawal management services, whereas older age (AOR: 0.81, 95% CI: 0.7–0.94) was negatively associated with the outcome.

Conclusions

This study identified specific factors associated with accessing withdrawal management services. Current evidence suggests a need to re-examine the provision of withdrawal management services. Consideration needs to be given to redesigning access to care and bridging to evidence-based addiction treatment, particularly for highly vulnerable subpopulations, identified in this study as females and older people.

Patterns of Transmitted Drug Resistance and Virological Response to First-line Antiretroviral Treatment Among Human Immunodeficiency Virus-Infected People Who Use Illicit Drugs in a Canadian Setting

Background

Transmitted drug resistance (TDR) may compromise response to antiretroviral therapy (ART). However, there are limited data on TDR patterns and impacts among people who use illicit drugs (PWUD).

Methods

Data were drawn from 2 prospective cohorts of PWUD in Vancouver, Canada. We characterized patterns of TDR among human immunodeficiency virus (HIV)-infected PWUD, and assessed its impacts on first-line ART virological outcomes.

Results

Between 1996 and 2015, among 573 ART-naive PWUD (18% with recent HIV infection), the overall TDR prevalence was 9.8% (95% confidence interval [CI], 7.3%-12.2%), with an increasing trend over time, from 8.5% in 1996-1999 to 21.1% in 2010-2015 (P = .003), mainly driven by resistance to nonnucleoside reverse transcriptase inhibitors (NNRTIs). TDR-associated mutations were more common for NNRTIs (5.4%), followed by nucleoside reverse transcriptase inhibitors (3.0%) and protease inhibitors (1.9%). TDR prevalence was lower among recently infected PWUD (adjusted odds ratio, 0.39 [95% CI, .15-.87]). Participants with TDR had higher risk of virological failure than those without TDR (log-rank P = .037) in the first year of ART.

Conclusions

Between 1996 and 2015, TDR prevalence increased significantly among PWUD in Vancouver. Higher risk of virological failure among PWUD with TDR may be explained by some inappropriate ART prescribing, as well as undetected minority resistant variants in participants with chronic HIV infection. Our findings support baseline resistance testing early in the course of HIV infection to guide ART selection among PWUD in our setting.

Factors associated with discontinuation of methadone maintenance therapy (MMT) among persons who use alcohol in Vancouver, Canada

BACKGROUND

We sought to examine the factors associated with discontinuation of MMT among persons on methadone who use alcohol.

METHODS

We evaluated the impact of drug-related and other factors on discontinuation of MMT among persons enrolled in MMT and who reported any use of alcohol versus those who were enrolled in two community-recruited prospective cohorts of people who use illicit drugs (PWUD). Extended Cox models with time-dependent variables identified factors independently associated with time to first MMT discontinuation.

RESULTS

Between December 2005 and 2015, 823 individuals on MMT who also reported using alcohol at least once were included in these analyses. During the study period, 391 (47.5%) discontinued methadone. Daily heroin injection (Adjusted Hazard Ratio [AHR] = 2.67, 95% Confidence Interval [CI]: 2.10-3.40) and homelessness (AHR = 1.42, 95% CI: 1.10-1.83) were positively associated with MMT discontinuation, whereas receiving other concurrent addiction treatment in addition to MMT (AHR = 0.07, 95% CI: 0.05-0.08), as well as >60 mg methadone dose (AHR = 0.48, 95% CI: 0.39-0.60), Hepatitis C virus seropositivity (AHR = 0.65, 95% CI: 0.47-0.90), and HIV seropositivity (AHR = 0.72, 95% CI: 0.57-0.91) were negatively associated with MMT discontinuation. Any/heavy alcohol use was not independently associated with MMT discontinuation.

CONCLUSIONS

This study reinforces the known risks of continued heroin injection and homelessness for MMT discontinuation among individuals who also consume alcohol and highlights the protective effect of both MMT dose and receipt of concurrent addiction treatment.

The impact of methadone maintenance therapy on access to regular physician care regarding hepatitis C among people who inject drugs

Background & aims

People who inject drugs (PWID) living with hepatitis C virus (HCV) infection often experience barriers to accessing HCV treatment and care. New, safer and more effective direct-acting antiviral-based therapies offer an opportunity to scale-up HCV-related services. Methadone maintenance therapy (MMT) programs have been shown to be effective in linking PWID to health and support services, largely in the context of HIV. The objective of the study was to examine the relationship between being enrolled in MMT and having access to regular physician care regarding HCV among HCV antibody-positive PWID in Vancouver, Canada.

Design

Three prospective cohort studies of people who use illicit drugs.

Setting

Vancouver, Canada.

Participants

We restricted the study sample to 1627 HCV-positive PWID between September 2005 and May 2015.

Measurements

A marginal structural model using inverse probability of treatment weights was used to estimate the longitudinal relationship between being enrolled in MMT and having a regular HCV physician and/or specialist.

Findings

In total, 1357 (83.4%) reported having access to regular physician care regarding HCV at least once during the study period. A marginal structural model estimated a 2.12 (95% confidence interval [CI]: 1.77–2.20) greater odds of having a regular HCV physician among participants enrolled in MMT compared to those not enrolled.

Conclusions

HCV-positive PWID who enrolled in MMT were more likely to report access to regular physician care regarding HCV compared to those not enrolled in MMT. These findings demonstrate that opioid agonist treatment may be helpful in linking PWID to HCV care, and highlight the need to better engage people who use drugs in substance use care, when appropriate.

Hospitalization among street-involved youth who use illicit drugs in Vancouver, Canada: a longitudinal analysis

Background

Street-involved youth who use illicit drugs are at high risk for health-related harms; however, the profile of youth at greatest risk of hospitalization has not been well described. We sought to characterize hospitalization among street-involved youth who use illicit drugs and identify the most frequent medical reasons for hospitalization among this population.

Methods

From January 2005 to May 2016, data were collected from the At-Risk Youth Study (ARYS), a prospective cohort study of street-involved youth in Vancouver, Canada. Multivariable generalized estimating equation (GEE) was used to identify factors associated with hospitalization.

Results

Among 1216 participants, 373 (30.7%) individuals reported hospitalization in the previous 6 months at some point during the study period. The top three reported medical reasons for hospital admission were the following: mental illness (37.77%), physical trauma (12.77%), and drug-related issues (12.59%). Factors significantly associated with hospitalization were the following: past diagnosis of a mental illness (adjusted odds ratio [AOR] = 1.85; 95% confidence interval [95% CI] 1.47–2.33), frequent cocaine use (AOR = 2.15; 95% CI 1.37–3.37), non-fatal overdose (AOR = 1.76; 95% CI 1.37–2.25), and homelessness (AOR = 1.40; 95% CI 1.16–1.68) (all p < 0.05).

Conclusions

Findings suggest that mental illness is a key driver of hospitalization among our sample. Comprehensive approaches to mental health and substance use in addition to stable housing offer promising opportunities to decrease hospitalization among this vulnerable population.

Substance use patterns associated with recent exposure to fentanyl among people who inject drugs in Vancouver, Canada: A cross-sectional urine toxicology screening study

INTRODUCTION

Vancouver, Canada is experiencing an opioid overdose crisis where fentanyl, a potent, synthetic opioid contaminating the illicit drug supply, has been detected in the majority of fatal overdose cases. Despite its growing presence throughout North America, few studies have characterized exposure to fentanyl among people who use illicit drugs (PWUD). We sought to identify the prevalence and correlates of fentanyl exposure among PWUD in Vancouver.

METHODS

Data were derived from cohort studies of PWUD in Vancouver. In June-October 2016, we administered multi-panel urine drug screens (UDS) to detect recent exposure to fentanyl and eight other substances. Multivariable logistic regression was used to identify substance use patterns associated with recent fentanyl exposure among participants who injected drugs in the past six months (PWID).

RESULTS

Among 669 PWUD including 250 (37.4%) females and 452 (67.6%) PWID, 97 (14.5%) tested positive for fentanyl. All these individuals also tested positive for other substances, most commonly for morphine/heroin (89.9%), amphetamine/methamphetamine (75.3%) and cocaine (74.2%). A fentanyl detection rate was significantly higher among PWID (19.7%) compared to non-injection drug users (3.9%) (p<0.001). In multivariable analyses, younger age (adjusted odds ratio [AOR]: 0.96) and testing positive for morphine/heroin (AOR: 6.73), buprenorphine (AOR: 4.25), amphetamine/methamphetamine (AOR: 3.26), cocaine (AOR: 2.92) and cannabis (AOR: 0.52) remained independently associated with fentanyl exposure (all p<0.05).

CONCLUSION

With one in five PWID being exposed to fentanyl, there is an urgent need to design and scale up interventions to reduce overdose risk, including a range of opioid agonist therapies.

Prevalence of Heavy Alcohol Use Among People Receiving Methadone Following Change to Methadose

BACKGROUND

A recent switch in methadone formulation from methadone (1 mg/mL) to Methadose (10 mg/mL) in British Columbia (BC), Canada, was associated with increased reports of opioid withdrawal and increases in illicit opioid use. Impacts on other forms of drug use have not been assessed. Since alcohol use is common among people receiving Medication-Assisted Treatment (MAT), we assessed if switch was associated with increased prevalence of heavy alcohol use.

METHODS

Drawing on data from two open prospective cohort studies of people who inject drugs in Vancouver, BC, generalized estimating equations (GEE) model examined relationship between methadone formulation change and heavy alcohol use, defined by National Institute for Alcohol Abuse and Alcoholism (NIAAA). A sub-analysis examined relationship with heavier drinking defined as at least eight drinks per day on average in last six months.

RESULTS

Between June 2013 and May 2015, a total of 787 participants on methadone were eligible for the present analysis, of which 123 (15.6%) reported heavy drinking at least once in last six months. In an unadjusted GEE model, Methadose use was not significantly associated with an increased likelihood of heavy drinking [Odds Ratio (OR) = 1.03; 95% Confidence interval (CI) = 0.87-1.21]. Methadose use was not significantly associated with an increased likelihood of drinking at least eight drinks daily on average (OR = 1.09, 95% CI = 0.72-1.65).

CONCLUSIONS

Despite reported changes in opioid use patterns coinciding with the change, there appeared to be no effect of the methadone formulation change on heavy drinking in this setting.

Major depressive disorder and access to health services among people who use illicit drugs in Vancouver, Canada

BACKGROUND

People who use illicit drugs (PWUD) are commonly diagnosed with major depressive disorder (MDD). However, little is known about whether PWUD living with MDD experience additional barriers to accessing health services compared to those without MDD. We sought to identify whether MDD symptoms were associated with perceived barriers to accessing health services among people who use illicit drugs (PWUD) in Vancouver, Canada.

METHODS

Data were collected through prospective cohorts of PWUD in Vancouver, Canada between 2005 and 2016. Using multiple logistic regression, we examined the relationship between MDD symptoms, defined as a Centre for Epidemiologic Studies Depression (CES-D) scale total score of ≥16, and barriers to access health services. We also used descriptive statistics to examine common barriers among participants who reported any barriers.

RESULTS

Among a total of 1529 PWUD, including 521 (34.1%) females, 415 (27.1%) reported barriers to accessing health services, and 956 (62.5%) reported MDD symptoms at baseline. In multiple logistic regression analyses, after adjusting for a range of potential confounders, MDD symptoms (adjusted odds ratio [AOR] = 1.40; 95% confidence interval [CI]: 1.03-1.92) were positively and significantly associated with barriers to accessing health services. Among those who reported MDD symptoms and barriers to access, commonly reported barriers included: long wait lists/times (38.1%); and treated poorly by health care professionals (30.0%).

CONCLUSION

These findings show that the likelihood of experiencing barriers to accessing health services was higher among PWUD with MDD symptoms compared to their counterparts. Policies and interventions tailored to address these barriers are urgently needed for this subpopulation of PWUD.

Nonmedical prescription opioid use and illegal drug use: initiation trajectory and related risks among people who use illegal drugs in Vancouver, Canada

Objective

We investigated the prevalence of and risk factors associated with initiating nonmedical prescription opioid use (NMPOU) before and after illegal drugs using data from two linked cohort studies of street youth and adults who use illegal drugs in Vancouver, Canada. All participants who attended a study visit between 2013 and 2016 were eligible for the primary analyses.

Results

Among 512 youth and 833 adult participants, the prevalence of NMPOU was extremely high (88% among street youth; 90% among adults), and over one-third of those who reported engaging in NMPOU had initiated NMPOU before illegal drug use (vs. transitioning from illegal drugs to NMPOU). Participants who reported either transitioning to or from NMPOU had higher risk profiles, particularly related to substance use, when compared with those who reported never engaging in NMPOU. Sub-analyses restricted to only those who engaged in NMPOU found few statistically significant differences between those who initiated NMPOU prior to illegal drugs versus those who initiated illegal drugs prior to NMPOU. Findings suggest that among people who use illegal drugs, early NMPOU trajectories do not appear to critically shape future patterns and practices.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3152-9) contains supplementary material, which is available to authorized users.

Knowledge and possession of take-home naloxone kits among street-involved youth in a Canadian setting: a cohort study

BACKGROUND

The distribution of take-home naloxone (THN) kits has been an important strategy in reducing overdose fatalities among people who use drugs. However, little is known about the use of THN among youth who are street-involved. The present study explores knowledge and possession of THN among street-involved youth in a Canadian setting.

METHODS

Data were derived from the At-Risk Youth Study (ARYS), a prospective cohort of street-involved youth age 14-28 at enrollment in Vancouver, Canada. Participants completed a standardized questionnaire, which included items related to knowledge and possession of THN, sociodemographic characteristics, and substance use-related factors. Multivariable logistic regression models were used to identify factors independently associated with knowledge and possession of THN.

RESULTS

Between December 2014 and November 2016, 177 youth were interviewed, including 68 females (38.4%). While 126 (71.2%) participants reported knowledge of THN, only 40 (22.6%) possessed a THN kit. Caucasian/white ethnicity was found to be positively associated with both knowledge and possession of THN (both p < 0.05). Public injection drug use in the last 6 months was found to be positively associated with knowledge of THN, while daily heroin use and daily methamphetamine use were associated with possession of THN (all p < 0.05). Male gender was negatively associated with possession of THN (p < 0.05).

CONCLUSIONS

These findings highlight important gaps between knowledge and possession of THN among youth and the need to increase participation in THN programs among specific populations including non-white and male youth. Further research is needed to gain a better understanding of the barriers that may prevent certain youth from acquiring THN kits.

Socioeconomic factors associated with cessation of injection drug use among street-involved youth

Background

Although the initiation of injection drug use has been well characterized among at-risk youth, factors that support or impede cessation of injection drug use have received less attention. We sought to identify socioeconomic factors associated with cessation of injection drug use among street-involved youth.

Methods

From September 2005 to May 2015, data were collected from the At-Risk Youth Study (ARYS), a prospective cohort study of street-involved youth in Vancouver, Canada. Multivariate extended Cox regression was utilized to identify socioeconomic factors associated with cessation of injection drug use for six months or longer among youth who were actively injecting.

Results

Among 383 participants, 171 (44.6%) youth reported having ceased injection (crude incidence density 22 per 100 person-years; 95% confidence interval [CI], 19–26) at some point during study follow-up. Youth who had recently dealt drugs (adjusted hazard ration [AHR], 0.50; 95% CI, 0.29–0.87), engaged in prohibited street-based income generation (AHR, 0.41; 95% CI, 0.24–0.69), and engaged in illegal income generating activities (AHR, 0.19; 95% CI, 0.06–0.61) were significantly less likely to report cessation of injection drug use.

Conclusions

Our findings suggest that socioeconomic factors, in particular engagement in prohibited street-based and illegal income generating activities, may pose barriers to ceasing injection drug use among this population. Effort to improve access to stable and secure income, as well as employment opportunities may assist youth in transitioning away from injection drug use.

Trial registration

Our study is not a randomized controlled trial; thus the trial registration is not applicable.

Incidence and predictors of mental health disorder diagnoses among people who inject drugs in a Canadian setting

INTRODUCTION AND AIMS

Limited attention has been given to the predictors of mental health diagnoses among people who inject drugs (PWID) in community settings. Therefore, we sought to longitudinally examine the prevalence, incidence and predictors of mental disorder diagnosis among a community-recruited cohort of PWID.

DESIGN AND METHODS

Data were derived from two prospective cohort studies of PWID (VIDUS and ACCESS) in Vancouver, Canada between December 2005 and May 2015. We used multivariable extended Cox regression to identify factors independently associated with self-reported mental disorder diagnosis during follow-up among those without a history of such diagnoses at baseline.

RESULTS

Among the 923 participants who did not report a mental disorder at baseline, 206 (22.3%) reported a first diagnosis of a mental disorder during follow-up for an incidence density of 4.29 [95% confidence interval (CI) 3.72-4.91] per 100 person-years. In the multivariable analysis, female sex [adjusted hazards ratio (AHR) = 1.74, 95% CI 1.29-2.33], experiencing non-fatal overdose (AHR = 2.33, 95% CI 1.38-3.94), accessing any drug or alcohol treatment (AHR = 1.68, 95% CI 1.24-2.27), accessing any community health or social services (AHR = 1.53, 95% CI 1.02-2.28) and experiencing violence (AHR = 1.60, 95% CI 1.12-2.29) were independently associated with a mental disorder diagnosis at follow-up.

DISCUSSION AND CONCLUSIONS

We observed a high prevalence and incidence of mental disorders among our community-recruited sample of PWID. The validity and implication of these diagnoses for key substance use and public health outcomes are an urgent priority.

Cessation of Injecting and Preceding Drug Use Patterns Among a Prospective Cohort of Street-Involved Youth

PURPOSE

Injection drug use is prevalent among street-involved youth, but patterns of cessation are poorly described. We identified drug use patterns preceding injection cessation among street-involved youth.

METHODS

From September 2005 to May 2015, we collected data from the At-Risk Youth Study, a prospective cohort of street-involved youth in Vancouver, Canada, and limited the sample to actively injecting youth. The primary outcome was cessation of injecting self-reported at semiannual follow-up visits. We used Cox regression to identify drug use patterns preceding cessation.

RESULTS

Among 383 youth, 65% were male, mean age was 22.3 (standard deviation, 2.5; range, 15-30) years, and 171 (45%) ceased injecting for 6 months or more (crude incidence density 22 per 100 person-years; 95% confidence interval [CI], 19-26). Youth who ceased were less likely to have injected daily (adjusted hazard ratio [AHR], .40; 95% CI, .28-.56), injected heroin (AHR, .40; 95% CI, .29-.56), or injected crystal methamphetamine (AHR, .43; 95% CI, .31-.59) before cessation. Noninjection heroin use was positively associated with injection cessation (AHR, 1.52; 95 CI, 1.12-2.08). Addiction treatment was not associated with cessation. At the time of cessation, 101 (59%) youth continued to use "hard" noninjection drugs such as heroin and crystal methamphetamine.

CONCLUSIONS

Periods of injection cessation were common but frequently accompanied by ongoing noninjection drug use. Findings indicate that trajectories of injection drug use among youth are complex and highlight the need to further explore relationships between ongoing noninjection drug use and injection cessation.