The impact of the COVID-19 pandemic on people who use drugs in three Canadian cities: a cross-sectional analysis.

BACKGROUND: The COVID-19 pandemic had a disproportionate impact on the health and wellbeing of people who use drugs (PWUD) in Canada. However less is known about jurisdictional commonalities and differences in COVID-19 exposure and impacts of pandemic-related restrictions on competing health and social risks among PWUD living in large urban centres. METHODS: Between May 2020 and March 2021, leveraging infrastructure from ongoing cohorts of PWUD, we surveyed 1,025 participants from Vancouver (n = 640), Toronto (n = 158), and Montreal (n = 227), Canada to describe the impacts of pandemic-related restrictions on basic, health, and harm reduction needs. RESULTS: Among participants, awareness of COVID-19 protective measures was high; however, between 10 and 24% of participants in each city-specific sample reported being unable to self-isolate. Overall, 3-19% of participants reported experiencing homelessness after the onset of the pandemic, while 20-41% reported that they went hungry more often than usual. Furthermore, 8-33% of participants reported experiencing an overdose during the pandemic, though most indicated no change in overdose frequency compared the pre-pandemic period. Most participants receiving opioid agonist therapy in the past six months reported treatment continuity during the pandemic (87-93%), however, 32% and 22% of participants in Toronto and Montreal reported missing doses due to service disruptions. There were some reports of difficulty accessing supervised consumption sites in all three sites, and drug checking services in Vancouver. CONCLUSION: Findings suggest PWUD in Canada experienced difficulties meeting essential needs and accessing some harm reduction services during the COVID-19 pandemic. These findings can inform preparedness planning for future public health emergencies.

Determinants of psychological distress during the COVID-19 pandemic among people who use drugs in Montreal, Canada.

INTRODUCTION: Limited data exists on psychological impacts of the COVID-19 pandemic among people who use drugs (PWUD). This study aimed to determine the prevalence and correlates of severe psychological distress (PD) among PWUD in Montreal around the beginning of the pandemic. METHODS: We conducted a rapid assessment study from May to December 2020 among PWUD recruited via a community-based cohort of people who inject drugs in Montreal (Hepatitis C cohort [HEPCO], N = 128) and community organisations (N = 98). We analysed self-reported data on changes in drug use behaviours and social determinants since the declaration of COVID-19 as a public health emergency, and assessed past-month PD using the Kessler K6 scale. Multivariable logistic regression was conducted to examine correlates of PD distress (score ≥13). RESULTS: Of 226 survey participants, a quarter (n = 56) were screened positive for severe PD. In multivariable analyses, age (1-year increment) (adjusted odds ratio = 0.94, 95% confidence interval [0.90, 0.98]) and a decrease in non-injection drug use versus no change (0.26 [0.07, 0.92]) were protective against severe PD, while positive associations were found for any alcohol use in the past 6 months (3.73 [1.42, 9.78]), increased food insecurity (2.88 [1.19, 6.93]) and both moving around between neighbourhoods more (8.71 [2.63, 28.88]) and less (3.03 [1.18, 7.74]) often compared to no change. DISCUSSION AND CONCLUSIONS: This study documented a high prevalence of severe PD among PWUD during the COVID-19 pandemic compared with pre-COVID-19 data. Social determinants such as food insecurity and mobility issues, alongside demographic and substance use-related factors, were linked to distress. Evidence-based risk mitigation strategies for this population could reduce negative consequences in future pandemics or disruptions.

Gender, sexual orientation identity, and initiation of amphetamine injecting among people who inject drugs: Examination of an expanding drug era in Montreal, Canada, 2011-19.

BACKGROUND: Amphetamine injection is expanding in North America and has been associated with male homosexuality among people who inject drugs (PWID). Applying subcultural evolution theory, we examined overall and gender-stratified trends in amphetamine injection and assessed sexual orientation as a gender-specific predictor of initiation among PWID in Montreal, Canada. METHODS: Data were from HEPCO, an open prospective cohort of PWID. Gender and sexual orientation were self-identified at enrolment. Interviewer-administered questionnaires at three-monthly (HCV RNA-negative participants) or yearly (RNA-positive) intervals captured past three-month amphetamine injection and covariates. Annual prevalence and linear trends in amphetamine injection were estimated using GEE. Incidence was computed among naïve individuals and hazard ratios for initiation estimated using gender-stratified, time-varying Cox regression models. RESULTS: 803 participants contributed 8096 observations between March 2011 and December 2019. Annual prevalence of amphetamine injecting increased from 3.25% [95%CI: 2.06-4.43%] to 12.7% [9.50-16.0] (trend p<0.001). Bivariate Cox regression models suggested similar and divergent predictors of initiation by gender. Incidence was 3.27 per 100 person-years [95%CI: 2.51-4.18] among heterosexual men, 7.18 [3.50-13.2] among gay/bisexual men, 1.93 [0.78-4.02] among heterosexual women and 5.30 [1.69-12.8] among gay/bisexual women. Among men, gay/bisexual identity doubled risk of initiation after adjusting for age, ethnicity, calendar year (aHR 2.16 [1.07-4.36]) and additional covariates (2.56 [1.24-5.30]). Among women, evidence for an association with gay/bisexual identity was inconclusive (aHR 2.63 [0.62-11.2]) and sample size precluded further adjustment CONCLUSIONS: Prevalence of amphetamine injection among PWID increased four-fold from 2011 to 2019, with elevated risk of initiation in gay and bisexual men.

Proactive Contact Tracing.

The COVID-19 pandemic has spurred an unprecedented demand for interventions that can reduce disease spread without excessively restricting daily activity, given negative impacts on mental health and economic outcomes. Digital contact tracing (DCT) apps have emerged as a component of the epidemic management toolkit. Existing DCT apps typically recommend quarantine to all digitally-recorded contacts of test-confirmed cases. Over-reliance on testing may, however, impede the effectiveness of such apps, since by the time cases are confirmed through testing, onward transmissions are likely to have occurred. Furthermore, most cases are infectious over a short period; only a subset of their contacts are likely to become infected. These apps do not fully utilize data sources to base their predictions of transmission risk during an encounter, leading to recommendations of quarantine to many uninfected people and associated slowdowns in economic activity. This phenomenon, commonly termed as "pingdemic," may additionally contribute to reduced compliance to public health measures. In this work, we propose a novel DCT framework, Proactive Contact Tracing (PCT), which uses multiple sources of information (e.g. self-reported symptoms, received messages from contacts) to estimate app users' infectiousness histories and provide behavioral recommendations. PCT methods are by design proactive, predicting spread before it occurs. We present an interpretable instance of this framework, the Rule-based PCT algorithm, designed via a multi-disciplinary collaboration among epidemiologists, computer scientists, and behavior experts. Finally, we develop an agent-based model that allows us to compare different DCT methods and evaluate their performance in negotiating the trade-off between epidemic control and restricting population mobility. Performing extensive sensitivity analysis across user behavior, public health policy, and virological parameters, we compare Rule-based PCT to i) binary contact tracing (BCT), which exclusively relies on test results and recommends a fixed-duration quarantine, and ii) household quarantine (HQ). Our results suggest that both BCT and Rule-based PCT improve upon HQ, however, Rule-based PCT is more efficient at controlling spread of disease than BCT across a range of scenarios. In terms of cost-effectiveness, we show that Rule-based PCT pareto-dominates BCT, as demonstrated by a decrease in Disability Adjusted Life Years, as well as Temporary Productivity Loss. Overall, we find that Rule-based PCT outperforms existing approaches across a varying range of parameters. By leveraging anonymized infectiousness estimates received from digitally-recorded contacts, PCT is able to notify potentially infected users earlier than BCT methods and prevent onward transmissions. Our results suggest that PCT-based applications could be a useful tool in managing future epidemics.

HCV treatment initiation in the era of universal direct acting antiviral coverage - Improvements in access and persistent barriers.

BACKGROUND: Barriers to HCV treatment initiation persisted after the introduction of direct-acting antivirals (DAAs) in Canada among people who inject drugs (PWID); whether DAA universal coverage lifted these barriers remain unknown. We assessed the evolution of HCV treatment initiation and associated factors among PWID in Montreal, Canada, comparing eras of IFN-based regimens (2011-2013), of DAA restricted access (2014-02/2018), and universal coverage (03/2018-03/2020). METHODS: We included chronically HCV-infected participants followed in a community-based PWID cohort in Montreal, Canada between 2011 and 03/2020 and collected data at 3-month intervals. Time-updated Cox regressions were conducted to examine 9 variables of interest associated with treatment initiation overall and for each of the three eras. RESULTS: Of 276 participants, 126 initiated treatment during follow-up. Yearly initiation increased from 3% in 2011 to 19% in 2016, and 54% in 2018. PWID aged >40 (vs. ≤40) were twice as likely to initiate treatment in 2014-02/2018 (HR: 2.02 95%CI: [1.24-3.28]) but not in other periods (2011-2013: 0.55 [0.25-1.22]; 03/2018-03/2020: 1.14 [0.59-2.22])). Odds of initiation were lower for men than women in all periods, with women three times more likely to be treated under universal coverage (0.30 [0.11-0.77] vs 2011-2013: 0.67 [0.25-1.78] and 2014-02/2018: 0.75 [0.42-1.35]). Recent incarceration was negatively associated with initiation throughout all periods (2011-2013: 0.57 [0.13-2.43]; 2014-03/2018: 0.39 [0.17-0.91]; 03/2018-03/2020: 0.25 [0.07-0.83]). Barriers associated with high injection frequency appear to have diminished since DAA introduction (2014-02/2018: 0.71 [0.42-1.20]; 03/2018-03/2020: 1.05 [0.52-2.11] vs. 2011-2013: 0.26 [0.08-0.88]). Contact with a primary care physician and engagement in opioid agonist therapy were positively associated with treatment initiation, though estimates were attenuated under universal coverage relative to previous eras. CONCLUSION: Treatment initiation rates have increased since the introduction of universal DAA coverage, though barriers such as incarceration persist.

Self-reported impacts of the COVID-19 pandemic among people who use drugs: a rapid assessment study in Montreal, Canada.

BACKGROUND: People who use drugs (PWUD) are at high risk of experiencing indirect harms of measures implemented to curb the spread of COVID-19, given high reliance on services and social networks. This study aimed to document short-term changes in behaviours and health-related indicators among PWUD in Montreal, Canada following declaration of a provincial health emergency in Quebec. METHODS: We administered a structured rapid assessment questionnaire to members of an existing cohort of PWUD and individuals reporting past-year illicit drug use recruited via community services. Telephone and in-person interviews were conducted in May-June and September-December 2020. Participants were asked to report on events and changes since the start of the health emergency (March 13, 2020). Descriptive analyses were performed. RESULTS: A total of 227 participants were included (77% male, median age = 46, 81% Caucasian). 83% and 41% reported past six-month illicit drug use and injection drug use, respectively. 70% of unstably housed participants reported increased difficulty finding shelter since the start of the health emergency. 48% of opioid agonist treatment recipients had discussed strategies to avoid treatment disruptions with providers; 22% had missed at least one dose. Many participants perceived increased difficulty accessing non-addiction health care services. Adverse changes were also noted in indicators pertaining to income, drug markets, drug use frequency, and exposure to violence; however, many participants reported no changes in these areas. Among persons reporting past six-month injection drug use, 79% tried to access needle-syringe programmes during the health emergency; 93% of those obtained services. 45% tried to access supervised injection sites, of whom 71% gained entry. CONCLUSIONS: This snapshot suggests mixed impacts of the COVID-19 pandemic on PWUD in Montreal in the months following declaration of a provincial health emergency. There were signals of increased exposure to high-risk environments as well as deteriorations in access to health services. Pandemic-related measures may have lasting impacts among vulnerable subgroups; continued monitoring is warranted.

Ageing and older people who use illicit opioids, cocaine or methamphetamine: a scoping review and literature map.

AIMS: To provide an overview of research literature on ageing and older people who use illicit opioids and stimulants by documenting the conceptual frameworks used and content areas that have been investigated. METHODS: We conducted a scoping review of literature relating to ageing and older people who use illicit stimulants and opioids, defining 'older' as 40 years and above. Primary studies, secondary studies and editorials were included. Searches were conducted in PubMed and Embase in July 2020 and March 2021; the Cochrane library was searched in November 2021. Charted data included methodological details, any conceptual frameworks explicitly applied by authors and the content areas that were the focus of the publication. We developed a hierarchy of content areas and mapped this to provide a visual guide to the research area. RESULTS: Of the 164 publications included in this review, only 16 explicitly applied a conceptual framework. Seven core content areas were identified, with most publications contributing to multiple content areas: acknowledgement of drug use among older people (n = 64), health status (n = 129), health services (n = 109), drug use practices and patterns (n = 84), social environments (n = 74), the criminal legal system (n = 28) and quality of life (n = 15). CONCLUSIONS: The literature regarding older people who use illicit drugs remains under-theorized. Conceptual frameworks are rarely applied and few have been purposely adapted to this population. Health status and health services access and use are among the most frequently researched topics in this area.

Injecting frequency trajectories and hepatitis C virus acquisition: Findings from a cohort of people who inject drugs in Montréal, Canada.

BACKGROUND: Frequent injecting increases hepatitis C (HCV) acquisition risk among people who inject drugs (PWID). However, few studies have examined how temporal fluctuations in injecting frequency may effect HCV infection risk. Thus, this study examined HCV incidence according to injecting frequency trajectories followed by PWID over one year in Montréal, Canada. METHODS: At three-month intervals from March 2011 to June 2016, HCV-uninfected PWID (never infected or cleared infection) enrolled in the Hepatitis Cohort (HEPCO) completed interviewer-administered questionnaires and HCV testing. At each visit, participants reported the number of injecting days (0-30 days) for each of the past three months. In previous work, using group-based trajectory modeling, we identified five injecting frequency trajectories followed by participants over one year (months 1-12 of follow-up), including sporadic, infrequent, increasing, decreasing, and frequent injecting. In this study, we estimated group-specific HCV incidence (months 1-63 of follow-up) using posterior probabilities to assign participants to their most likely trajectory group. RESULTS: Of 386 participants (mean age=40, 82% male, 48% never HCV-infected), 72 acquired HCV during 893 person-years of follow-up. HCV incidence for the whole study sample was 8.1 per 100 person-years (95%CI=6.4-10.1). Trajectory group-specific HCV incidences were highest for those injecting drugs with decreasing (23.9, 14.4-37.5) or increasing frequency (16.0, 10.1-24.3), intermediate for those injecting at consistently high frequency (10.2, 5.4-17.8), and lowest for those injecting infrequently (3.9, 2.2-6.5) or sporadically (4.3, 2.2-7.6). CONCLUSION: Results suggest that PWID at highest HCV risk are those injecting at high frequency, either transitorily (increasing, decreasing injecting) or consistently (frequent injecting). This study highlights changes in injecting frequency as a potentially important dimension to consider among the factors leading to HCV acquisition. Clinical and public health interventions tailored to PWID with different injecting frequency profiles may contribute to HCV prevention.

Gender-specific associations between psychological distress and injecting risk behaviours among people who inject drugs in Montreal, Canada.

BACKGROUND: Psychological distress is common among people who inject drugs (PWID) and may be associated with HCV-related risk behaviours. Previous studies have documented increased vulnerability to both psychological distress and HCV infection among female relative to male PWID. It is, however, unclear whether behavioural responses to distress differ by gender. This study estimated gender-specific associations between psychological distress and i) binge drug injection, and ii) sharing of injection materials. METHODS: Data were drawn from HEPCO, a longitudinal cohort study involving three-monthly interviews with active PWID in Montreal, Canada. Past-month psychological distress was assessed with the Kessler (K10) scale, categorized for descriptive analyses as minimal (score 10-15), moderate (16-21), high (22-29), or severe (30-50). Binge was defined as injecting large quantities of drugs until participants could no longer continue (past 3 months). Sharing was defined as injection with previously-used needles or equipment (past 3 months). Generalized additive models were fit to estimate smooth, nonlinear associations between K10 scores and risk behaviours, by gender. Models were adjusted for known determinants of drug-related harms and included random intercepts to model within-subject correlation. RESULTS: 805 individuals (82% male) provided 8158 observations (2011-2020). High to severe levels of distress were common and more frequent among women (55% vs 37%). Among men, the odds of binge and sharing monotonically and non-linearly increased with increasing scores of psychological distress. Associations for binge among women were attenuated relative to men but nevertheless increased with distress, albeit in a linear fashion. Sharing was not associated with distress among women. CONCLUSION: Psychological distress was differentially associated with injecting risk behaviours among men and women who inject drugs. Assessment of distress may provide novel prevention opportunities for select PWID. Further investigation into gender differences is warranted to inform development and tailoring of interventions.

Socioeconomic stability is associated with lower injection frequency among people with distinct trajectories of injection drug use.

BACKGROUND: Little is known about how socioeconomic circumstances relate to injection frequencies among people who inject drugs (PWID) with diverse trajectories of injection. We aimed to characterize trajectories of injection drug use in a community-based sample of PWID over 7.5 years and to investigate the extent to which two modifiable factors reflecting socioeconomic stability-stable housing and stable income-relate to injection frequencies across distinct trajectories. METHODS: HEPCO is an open, prospective cohort study of PWID living in Montréal with repeated follow-up at three-month or one-year intervals. Self-reported data on injection frequency, housing and income are collected at each visit. Injection frequency was defined as the number of injection days (0-30), reported for each of the past three months. Using group-based trajectory modeling, we first estimated average trajectories of injection frequency. Then, we estimated the trajectory group-specific average shift upward or downward associated with periods of stable housing and stable income relative to periods when these conditions were unstable. RESULTS: Based on 19,527 injection frequency observations accrued by 529 participants followed over 2011-2019 (18.3% female, median age: 41), we identified five trajectories of injection frequency: three characterized by sustained injection at different frequencies (28% infrequent; 19% fluctuating; 19% frequent), one by a gradual decline (12%), and another by cessation (28%). Periods of stable housing and stable income were each independently associated with a lower injection frequency, on average, in all five trajectory groups (2.2-7.5 fewer injection days/month, depending on the factor and trajectory group). CONCLUSION: Trajectories of injection drug use frequency were diverse and long-lasting for many PWID. Despite this diversity, socioeconomic stability was consistently associated with a lower injection frequency, emphasizing the close relationship between access to fundamental necessities and injection patterns in all PWID, irrespective of whether they are on a path to cessation or sustained injecting.

A rapid review of the impacts of "Big Events " on risks, harms, and service delivery among people who use drugs: Implications for responding to COVID-19.

BACKGROUND: "Big Events" are major disruptions to physical, political, and economic environments that can influence vulnerability to drug-related harms. We reviewed the impacts of Big Events with relevance to the COVID-19 pandemic on drug-related risk and harms and access to drug treatment and harm reduction services. METHODS: We conducted a rapid review of quantitative, qualitative, and mixed methods literature relating to the following Big Events: respiratory infection pandemics, natural disasters, financial crises, and heroin shortages. Included studies reported data on changes to risks, harms, and/or service provisioning for people who use illicit drugs (other than cannabis) in the context of these Big Events. Searches were conducted in PubMed in May 2020, and two reviewers screened studies for inclusion. Peer-reviewed studies published in English or French were included. We used a narrative synthesis approach and mapped risk pathways identified in the literature. RESULTS: No studies reporting on respiratory infection pandemics were identified. Twelve studies reporting on natural disaster outcomes noted marked disruption to drug markets, increased violence and risk of drug-related harm, and significant barriers to service provision caused by infrastructure damage. Five studies of the 2008 global financial crisis indicated increases in the frequency of drug use and associated harms as incomes and service funding declined. Finally, 17 studies of heroin shortages noted increases in heroin price and adulteration, potentiating drug substitutions and risk behaviors, as well as growing demand for drug treatment. CONCLUSION: Current evidence reveals numerous risk pathways and service impacts emanating from Big Events. Risk pathway maps derived from this literature provide groundwork for future research and policy analyses, including in the context of the COVID-19 pandemic. In light of the findings, we recommend responding to the pandemic with legislative and financial support for the flexible delivery of harm reduction services, opioid agonist treatment, and mental health care.

Deconstructing the 'cheque effect': short-term changes in injection drug use after receiving income assistance and associated factors.

BACKGROUND AND AIMS: Disbursement of income assistance has been temporally associated with intensified drug use and related harms (coined the 'cheque effect'). However, relationships to injection drug use (IDU) remain understudied. We examined short-term 'cheque effects' and associated factors among people who inject drugs (PWID). DESIGN: Cross-sectional analysis nested within a cohort study. SETTING: Montreal, Quebec, Canada. PARTICIPANTS: PWID receiving income assistance, with no employment income. A total of 613 PWID (median age 41, 83% male) contributed 3269 observations from 2011 to 2017. MEASUREMENTS AND METHODS: At each cohort visit, an interviewer-administered questionnaire captured retrospective reports of injection-related behaviour during the 2-day periods (i) before and (ii) including/after receiving last month's income assistance payment (number of injections; drugs injected; any receptive syringe-sharing). The relative likelihood (odds) and magnitude (rate) of an increase in injection frequency ('cheque effect') were estimated in relation to social and behavioural factors using logistic and negative binomial regression in a covariate-adjusted two-part model. FINDINGS: Prevalence of IDU and syringe-sharing were, respectively, 1.80 and 2.50 times higher in the days following versus preceding cheque receipt (P < 0.001). Among people with past-month IDU, most observations showed increased injection frequency (52%) or no change in injection frequency (44%). The likelihood of a 'cheque effect' was positively associated with cocaine injection [versus injection of other substances, odds ratio (OR) = 2.639, 95% confidence interval (CI) = 2.04-3.41], unstable housing (OR = 1.272, 95% CI = 1.03-1.57) and receiving opioid agonist therapy (OR =1.597, 95% CI = 1.27-2.00) during the same month. Magnitude of the 'cheque effect' was positively associated with cocaine injection [rate ratio (RR) = 1.795, 95% CI = 1.43-2.16], unstable housing (RR = 1.198, 95% CI = 1.02-1.38) and frequent injection (RR = 2.938, 95% CI = 2.43-3.44), but inversely associated with opioid agonist therapy (RR = 0.817, 95% CI = 0.68-0.95) and prescription opioid injection (RR = 0.794, 95% CI = 0.66-0.93). CONCLUSION: Among people who inject drugs in Montreal, Canada, injection drug use and receptive syringe-sharing appear to be more prevalent in the 2 days after versus before receiving income assistance. The odds and rate of individual-level increases in injection frequency appear to be positively associated with cocaine injection (versus injection of other substances) and unstable housing.

Harm Reduction Coverage and Hepatitis C Incidence: Findings From a Cohort of People Who Inject Drugs.

INTRODUCTION: Needle and syringe programs and opioid agonist therapy are essential for harm reduction among people who inject drugs. Few studies assess their combined potential in preventing hepatitis C virus infection. No studies have assessed whether they perform similarly among individuals at risk of primary and recurrent infection. This study aimed to estimate the rates of hepatitis C virus acquisition according to harm reduction coverage among hepatitis C virus-naive and previously infected people who inject drugs in Montreal, Canada. METHODS: This prospective cohort study involved regular interviews and hepatitis C antibody and RNA testing (data collection: 2010-2017, analysis: 2018). Opioid agonist therapy coverage was defined by current dose: high (≥60 mg/day methadone, ≥16 mg buprenorphine), low, or none. Complete needle and syringe program coverage was defined as exclusively reporting safe needle and syringe sources (past 6 or 3 months). Combined coverage was defined as full (high-dose agonist/complete needle/syringe coverage), minimal (low-dose agonist/incomplete needle/syringe coverage), and partial (remaining combinations). Cox regression models were fit. RESULTS: A total of 106 events were observed over 1,183.1 person-years for primary and recurrent incidence rates of 10.6 (95% CI=8.0, 13.8) and 7.6 (95% CI=5.6, 9.9) per 100 years, respectively. High-dose opioid agonist therapy was associated with a 77% reduction in hepatitis C virus acquisition (hazard ratio=0.23, 95% CI=0.10, 0.50) compared with not receiving opioid agonist therapy. Needle and syringe coverage was not associated with infection rates. Estimates considering their combination reflected opioid agonist therapy coverage. Associations were similar among hepatitis C virus-naive and previously infected people who inject drugs. CONCLUSIONS: High-dose opioid agonist therapy seems particularly important to reduce drug-related harms among hepatitis C virus-naive and previously infected people who inject drugs in Montreal.

Cigarette Smoking and Nicotine Dependence Trajectories Among Incident Adolescent Smokers.

INTRODUCTION: Few interventions target adolescent cigarette smokers to prevent escalation in cigarette use or promote cessation, in part because little is known about co-developing smoking and nicotine dependence (ND). Our objectives were to: (1) estimate developmental trajectories of ND/cravings, withdrawal symptoms, the modified Fagerström Tolerance Questionnaire (mFTQ) and ICD-10 tobacco dependence in incident adolescent smokers; (2) describe concordance in number and shapes of trajectories across the four ND indicators; and (3) classify participants in each ND trajectory according to cigarette smoking trajectories. METHODS: Data were drawn from an ongoing longitudinal investigation of 1294 grade 7 students recruited in 1999-2000 in 10 Montreal-area high schools. Group-based joint trajectory models were used to identify distinct subgroups defined by the four ND indicators, in 307 incident smokers. RESULTS: The optimal trajectory model included five groups for ND/craving and four groups for each of withdrawal symptoms, the mFTQ and ICD-10 tobacco dependence. The four ND indicators showed similar developmental patterns and classification into smoking trajectory groups, although some discordance was observed. Smokers in the low-level decreaser group and stable low consumers who exhibited high ND were younger than those in the cigarette-low ND trajectory groups. Moderate or rapid escalators who exhibited no/low ND were less likely to have university-educated mothers and more likely to have parents who smoke. CONCLUSIONS: Trajectories were similar across ND indicators, and generally reflected cigarette smoking trajectory shapes. Novice smokers may need education to become self-aware of developing ND symptoms, as well as to learn about alternative courses of action once ND symptoms manifest. IMPLICATIONS: Trajectories of cigarette smoking and ND symptoms have rarely been investigated concurrently. This study provides evidence of high concordance across four distinct ND indicators in the proportion of participants with no/low-level dependence, and with high or increasing ND. Moreover, the development of cigarette smoking is concordant with ND symptom development. Interventions to prevent escalation and promote cessation should target adolescents before first puff to increase self-awareness of developing ND symptoms, as well as to learn about alternative courses of action once ND symptoms are experienced.

Associations between housing stability and injecting frequency fluctuations: findings from a cohort of people who inject drugs in Montréal, Canada.

BACKGROUND: The relationship between housing stability and drug injecting is complex, as both outcomes fluctuate over time. The objectives were to identify short-term trajectories of housing stability and injecting frequency among people who inject drugs (PWID) and examine how patterns of injecting frequency relate to those of housing stability. METHODS: At three-month intervals, PWID enrolled between 2011 and 2016 in the Hepatitis Cohort completed an interviewer-administered questionnaire and were tested for hepatitis C and HIV infections. At each visit, participants reported, for each of the past three months, the accommodation they lived in the longest (stable/unstable) and the number of injecting days (0-30). Group-based dual trajectory modeling was conducted to identify housing stability and injecting frequency trajectories evolving concomitantly over 12 months and estimate the probabilities of following injecting trajectories conditional upon housing trajectories. RESULTS: 386 participants were included (mean age 40.0, 82 % male). Three housing stability trajectories were identified: sustained (53 %), declining (20 %), and improving (27 %). Five injecting frequency trajectories were identified: sporadic (26 %), infrequent (34 %), increasing (15 %), decreasing (11 %), and frequent (13 %). PWID with improving housing were less likely to increase injecting (8 %) compared to those with sustained (17 %) or declining housing (17 %). CONCLUSIONS: Improving housing was associated with a lower probability of increasing injecting compared to declining housing, while sustained housing stability was associated with a higher probability of increasing injecting compared to improving housing. Therefore, policies to improve PWID's access to stable housing are warranted and may reduce, to some extent, drug injecting and related harms.

Sexual behaviour as a risk factor for hepatitis C virus infection among people who inject drugs in Montreal, Canada.

Hepatitis C virus (HCV) acquisition remains high in key risk environments including injection drug use and sex between men. However, few studies examine the independent contribution of sexual behaviour to HCV acquisition among people who inject drugs (PWID). We estimated HCV incidence and examined sexual behaviour as a time-varying predictor of HCV acquisition in a prospective cohort study of PWID in Montreal (2004-2017). Initially, HCV-negative participants completed behavioural questionnaires and HCV antibody testing (6 months until 2011, 3 months thereafter). A time-updating exposure variable (no sex, opposite-sex partner only, ≥1 same-sex partner) was generated for the previous 6/3 months. Time to HCV seroconversion was examined using Cox regression analysis, adjusted for age, unstable housing and incarceration (both past 3 months), and daily, heroin, cocaine and prescription opioid injecting (all past month). Among 440 PWID (baseline: median age 33 years, 18.9% female, 1.4% HIV-positive), 156 participants seroconverted during follow-up (overall incidence rate: 11.9/100 person-years [PY]). Incidence was lowest in the no sex group (8.70 and 2.91 cases/100 PY in males and females, respectively) and highest in the ≥1 same-sex partner group (24.14 and 21.97 cases/100 PY in males and females, respectively). Among males, HCV risk was 47% lower in those reporting no sex compared to ≥1 same-sex partner (adjusted hazard ratio: 0.53, 95% confidence interval: 0.28, 0.99). In this cohort of PWID, reporting recent same-sex partners was associated with greater risk of HCV acquisition among males, necessitating targeted harm reduction strategies that consider the complex interplay of sexual and injecting risk behaviours.

Opioid agonist treatment dosage and patient-perceived dosage adequacy, and risk of hepatitis C infection among people who inject drugs.

BACKGROUND: Opioid agonist treatment is considered important in preventing acquisition of hepatitis C virus (HCV) among people who inject drugs; however, the role of dosage in opioid agonist treatment is unclear. We investigated the joint association of prescribed dosage of opioid agonist treatment and patient-perceived dosage adequacy with risk of HCV infection among people who inject drugs. METHODS: We followed prospectively people who inject drugs at risk of acquiring HCV infection (who were RNA negative and HCV-antibody negative or positive) in Montréal, Canada (2004-2017). At 6-month, then 3-month intervals, participants were tested for HCV antibodies or RNA, and completed an interviewer-administered behavioural questionnaire, reporting the following: current exposure to opioid agonist treatment (yes/no), prescribed dosage either high (methadone ≥ 60 mg/d or buprenorphine ≥ 16 mg/d) or low, and perceived dosage adequacy (adequate/inadequate). We then assigned participants to 1 of 5 exposure categories: no opioid agonist treatment, high dosage of opioid agonist treatment perceived to be adequate, high dosage perceived to be inadequate, low dosage perceived to be adequate or low dosage perceived to be inadequate. To estimate associations between categories of opioid agonist treatment dosage and incident HCV infection, we conducted Cox regression analyses, adjusting for multiple confounding factors. RESULTS: Of 513 participants (median age 35.0 yr, 77.6% male), 168 acquired HCV over 1422.6 person-years of follow-up (incidence 11.8/100 person-years, 95% confidence interval [CI] 10.1-13.7). We observed a gradient in the relative risks of HCV infection across categories of opioid agonist treatment dosage. Compared with people who inject drugs not receiving opioid agonist treatment, adjusted hazard ratios were 0.43 (95% CI 0.23-0.84) for those receiving high dosages perceived to be adequate, 0.61 (95% CI 0.25-1.50) for those receiving high dosages perceived to be inadequate, 1.22 (95% CI 0.74-2.00) for those receiving low dosages perceived to be adequate and 1.94 (95% CI 1.11-3.39) for those receiving low dosages perceived to be inadequate. INTERPRETATION: Risk of HCV infection varies considerably according to dosage of opioid agonist treatment and patient-perceived adequacy, with associations indicating both protective and harmful effects relative to no exposure to opioid agonist treatment.

Transitioning from interferon-based to direct antiviral treatment options: A potential shift in barriers and facilitators of treatment initiation among people who use drugs?

BACKGROUND: Multiple barriers for accessing hepatitis C virus (HCV) treatment were identified during the interferon-based (IFN) treatment era for people who inject drugs (PWID). Whether these barriers persist since the introduction of IFN-free direct-acting antiviral (DAA) agents in Canada remains to be documented. This study examined temporal trends in HCV treatment initiation and associated factors during the transition from INF-based to all-oral DAA regimens. METHODS: The study population was drawn from a prospective cohort of PWID in Montreal, Canada. At three-month/one-year intervals between 2011 and 2017, participants with chronic HCV infection completed an interviewer-administered questionnaire on socio-demographic characteristics, drug use and health service utilisation, including HCV treatment. Time-updated Cox multivariate regression models, stratified by DAA + INF (2011-2013) and all-oral DAA (2014-2017) availability periods, were conducted to examine associations between time to HCV treatment initiation and associated barriers and facilitators. RESULTS: Of 308 participants (85% male, median age 42 [IQR: 33, 50]), 80 (26%) initiated HCV treatment during 915 person-years (PY). Incidence rates increased from 1.6 /100 PY (95%CI:0.9-2.6) in 2011 to 12.7 (10.6-15.1) in 2017 (p-trend = 0.0012). In multivariate analyses, visiting a primary care physician (2011-2013: aHR = 3.63[1.21-10.9]; 2014-2017: 2.52[1.10-5.77]) and frequent injection (0.23[0.05-0.99] and 0.49[0.24-0.99]) were consistently associated with treatment initiation. Participants aged >40 (2.27[1.24-4.13]), receiving opioid agonist therapy (OAT) (2.17[1.19-3.94]), and reporting prior HCV treatment (3.00[1.75-5.15]) were more likely to initiate treatment in the all-oral DAA period. CONCLUSION: Treatment initiation increased between 2011 and 2017, but still remains low among PWID. Primary care visiting was a key facilitator regardless of the period, while engagement in OAT and health services, indicated by prior HCV treatment, increased the likelihood of treatment initiation in the DAA era. These findings suggest that access to health services is essential but not enough to scale up treatment in this population.

Conceptualising access in the direct-acting antiviral era: An integrated framework to inform research and practice in HCV care for people who inject drugs.

As direct-acting antiviral (DAA) therapy costs fall and eligibility criteria are relaxed, people who inject drugs (PWID) will increasingly become eligible for HCV treatment. Yet eligibility does not necessarily equate to access. Amidst efforts to expand treatment uptake in this population, we seek to synthesise and clarify the conceptual underpinnings of access to health care for PWID, with a view to informing research and practice. Integrating dominant frameworks of health service utilisation, care seeking processes, and ecological perspectives on health promotion, we present a comprehensive theoretical framework to understand, investigate and intervene upon barriers and facilitators to HCV care for PWID. Built upon the concept of Candidacy, the framework describes access to care as a continually negotiated product of the alignment between individuals, health professionals, and health systems. Individuals must identify themselves as candidates for services and then work to stake this claim; health professionals serve as gatekeepers, adjudicating asserted candidacies within the context of localised operating conditions; and repeated interactions build experiential knowledge and patient-practitioner relationships, influencing identification and assertion of candidacy over time. These processes occur within a complex social ecology of interdependent individual, service, system, and policy factors, on which other established theories provide guidance. There is a pressing need for a deliberate and nuanced theory of health care access to complement efforts to document the HCV 'cascade of care' among PWID. We offer this framework as an organising device for observational research, intervention, and implementation science to expand access to HCV care in this vulnerable population. Using practical examples from the HCV literature, we demonstrate its utility for specifying research questions and intervention targets across multiple levels of influence; describing and testing plausible effect mechanisms; and identifying potential threats to validity or barriers to research translation.