Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico

Trends in drug overdose deaths in Mexico (1999-2019). A national descriptive analysis and interstate comparison

BACKGROUND

We assess trends in overdose mortality rates in Mexico from 1999 to 2019 and identify the states with the highest overdose mortality rates over time.

METHODS

The analysis using mortality statistics examined deaths related to drug use. We estimated general overdose mortality rates at the national and state levels and calculated specific mortality rates associated with opioid and stimulant use using central rate estimation. We used joinpoint regression to analyse national and state-specific trends in overdose mortality from 1999 to 2019.

FINDINGS

Nationally, the general overdose mortality rate increased annually by 10.49 % (p < 0.01, CI=11.4-18.9) from 2015 to 2019. The northern states of Baja California and Chihuahua were the states with the higher annual increases (18.6 %, p < 0.01, CI=4.2-29.6; and 15.6 %, p < 0.01, CI=12.9-19.7, respectively). By substance type, the national opioid-related mortality rate increased by 29.82 % per year from 2014 to 2019 (p < 0.01; CI=20.1-40.3), compared with an annual decrease of 11.43 % in the previous period (2005-2014) (p < 0.01; CI=-14.7- 8.0). Baja California was the state with the highest rise in opioid-related mortality from 2013 to 2019, with an annual increase of 15.84 % (p < 0.01; CI=1.4-32.3). Stimulant-related mortality increased by 21.79 % per year since 2013 (p < 0.01; CI=16.9-26.9), but it was not possible to calculate state-level trends.

CONCLUSIONS

Drug-related mortality rates have increased in Mexico since 2015, particularly in the northern states of Baja California, Chihuahua, Sonora and Sinaloa. Improving harm reduction programmes and local surveillance of fatal and non-fatal overdoses is essential to address the silent escalation of overdose mortality.

Health, harm reduction, and social service providers' perspectives on the appropriateness and feasibility of peer distribution of HIV self-test kits among people who use drugs

BACKGROUND

People who use drugs (PWUD) experience elevated HIV risk and numerous barriers to facility-based HIV testing. HIV self-testing (HIVST) could circumvent many of those barriers and is acceptable among PWUD, yet HIVST implementation for PWUD is limited. Service providers' perspectives on specific HIVST delivery strategies could help increase availability for PWUD.

METHODS

From April-November 2021, we interviewed 16 health, harm reduction, and social service providers working with PWUD in San Diego, CA. Interviews and rapid thematic analysis explored perspectives on HIVST's utility and appropriateness, as well as the feasibility of and anticipated challenges with specific HIVST delivery strategies, including peer or secondary distribution.

RESULTS

Participants viewed HIV as a significant threat to PWUD health and confirmed the presence of numerous barriers to local facility-based HIV testing. Participants viewed HIVST as a promising and potentially empowering solution. Based on community familiarity with secondary distribution of harm reduction supplies (i.e., naloxone) and information, participants viewed secondary distribution of HIVST kits as an appropriate and feasible strategy for increasing the reach of HIVST, but also described potential barriers (e.g., engaging socially disconnected individuals, ensuring linkages to services following HIVST) and provided suggestions for alternative HIVST kit delivery models (e.g., harm reduction vending machines).

CONCLUSIONS

Service providers viewed secondary distribution of HIVST kits among PWUD as promising, appropriate, and feasible, yet specialized efforts may be needed to reach the most marginalized individuals and ensure consistent provision of educational information and referral supports that maximize the impact of this approach.

Longitudinal polysubstance use patterns and non-fatal overdose: A repeated measures latent class analysis

BACKGROUND

Polysubstance use (PSU) is common among people who use opioids (PWUO) and has been associated with drug-related harms. We aimed to identify latent longitudinal PSU classes among a cohort of PWUO and characterize non-fatal overdose risks among different sub-classes over time.

METHODS

We used longitudinal data (2005-2018) from three ongoing prospective cohorts of people who use drugs in Vancouver, Canada. The primary outcome of interest was self-reported non-fatal overdose during the past six months. The primary exposure of interest was longitudinal PSU patterns among PWUO, obtained from repeated measures latent class analysis (RMLCA) of weekly substance use-related outcome indicators. Multivariable generalized estimating equations models were built to assess the association between latent PSU class membership and non-fatal overdose, adjusting for potential sociodemographic, behavioural, and structural confounders.

RESULTS

2627 PWUO were included in the analysis, and 1094 (41.6 %) had experienced at least one non-fatal overdose during the study period. RMLCA revealed five distinct latent longitudinal PSU classes, including low/infrequent use (Class 1; 30 %), primarily opioid and methamphetamine use (Class 2; 22 %), primarily cannabis use (Class 3; 15 %), primarily opioid and crack use (Class 4; 29 %), and frequent PSU (Class 5; 4 %). In comparison with Class 1 (low), membership in all latent PSU classes except Class 3 (cannabis) was associated with increased odds of non-fatal overdose: Class 2 (opioids + meth) vs. Class 1 (Adjusted odds ratios [aOR] = 2.20, 95 % confidence intervals [CI]: 1.51-3.22), Class 4 (opioids + crack) vs. Class 1 (aOR = 1.06, 95 % CI: 0.85-1.33), and Class 5 (frequent) vs. Class 1 (aOR = 2.39, 95 % CI: 1.92-2.97).

CONCLUSION

Our findings highlighted the heterogeneous characteristics of PWUO in terms of patterns of PSU and non-fatal overdose risk. The diverse nature of PWUO and the potential additive or multiplicative impact of using several substances on overdoses should be reflected across the substance use treatment continuum and care provision.

Willingness to use and distribute HIV self-testing kits among people who inject drugs in the San Diego-Tijuana border region

BACKGROUND

HIV self-testing (HIVST) could increase HIV testing access among people who inject drugs (PWID), and secondary distribution (i.e., peer-delivery) of HIVST kits in PWID social networks could further expand coverage. We assessed willingness to use and distribute HIVST kits among PWID in the San Diego-Tijuana border region.

METHODS

From 2020 to 2021, HIV-negative PWID in San Diego, USA, and Tijuana, Mexico, completed surveys and provided data on individual (N = 539) and social network (N = 366) characteristics. We used modified Poisson regression to examine the effects of individual and social network characteristics on willingness to use and distribute HIVST kits.

RESULTS

Most participants were willing to use (81%) and distribute (81%) HIVST kits. At the individual level, prior HIV testing was positively associated with willingness to use (adjusted prevalence ratio [aPR] = 1.24, 95% confidence interval [CI] 1.10-1.40) and distribute (aPR = 1.27, 95% CI 1.12-1.43) HIVST kits, while perceiving oneself to be at higher HIV risk than others was negatively associated with willingness to use HIVST kits (aPR = 0.83, 95% CI 0.74-0.93). At the network level, willingness to distribute HIVST kits was positively associated with network size (aPR = 1.04 per member, 95% CI 1.01-1.08) and greater proportions of one's network encouraging them to use drugs (aPR = 1.29, 95% CI 1.16-1.44) and having a history of homelessness (aPR = 1.51, 95% CI 1.31-1.74) or detention/arrest (aPR = 1.57, 95% CI 1.36-1.82), and negatively associated with a greater proportion of one's network including "very close" persons (aPR = 0.80, 95% CI 0.69-0.94).

CONCLUSIONS

We found high potential for HIVST kits and their secondary distribution to increase HIV testing among PWID who face the greatest barriers to facility-based testing.

Understanding polysubstance use at the daily and event levels: protocol for a mixed-methods qualitative and ecological momentary assessment study in a community-based sample of people who use illicit drugs in Oakland, California, USA

INTRODUCTION

Polysubstance use is extremely common among people who use illicit opioids in the USA. It is associated with poor substance use treatment outcomes, infectious disease risk and alarming rates of drug overdose. Nearly all extant literature examines polysubstance use over broad time frames, such as 30 days or 6 months. However, both substance use and overdose risk are episodic. To build a stronger understanding of polysubstance use and overdose risk, we need to expand the knowledge base to include daily-level and event-level data that examine how substances are used together, in which combinations and in which contexts. The study described in this protocol will use qualitative and ecological momentary assessment (EMA) methods to examine polysubstance use and overdose risk on a daily and event level.

METHODS AND ANALYSIS

This is a mixed-methods observational study with three phases. The first phase is formative, consisting of qualitative interviews with people who use multiple substances (N=20), to inform the development of items for the EMA component. The second phase is EMA data collection with people who use multiple substances (N=120), three times daily for 28 days. The third phase consists of mixed-methods inquiries with a subset of participants (N=20), using participant-level EMA data and qualitative techniques to build a nuanced understanding of the motivations and contexts of polysubstance use in everyday life. Analytical induction methods will be used to interpret qualitative data. Hierarchical linear modelling methods will be used to analyse EMA data.

ETHICS AND DISSEMINATION

This research has been reviewed and approved by the Institutional Review Board at RTI International (#MOD00001782 for EMA procedures and #MOD00001241 for qualitative procedures). Participants engage in an informed consent procedure for each component of the study. Data will be managed and shared per the National Institutes of Health extramural data sharing policy.

Latent polydrug use patterns and the provision of injection initiation assistance among people who inject drugs in three North American settings

INTRODUCTION

We sought to identify latent profiles of polysubstance use patterns among people who inject drugs in three distinct North American settings, and then determine whether profile membership was associated with providing injection initiation assistance to injection-naïve persons.

METHODS

Cross-sectional data from three linked cohorts in Vancouver, Canada; Tijuana, Mexico; and San Diego, USA were used to conduct separate latent profile analyses based on recent (i.e., past 6 months) injection and non-injection drug use frequency. We then assessed the association between polysubstance use patterns and recent injection initiation assistance provision using logistic regression analyses.

RESULTS

A 6-class model for Vancouver participants, a 4-class model for Tijuana participants and a 4-class model for San Diego participants were selected based on statistical indices of fit and interpretability. In all settings, at least one profile included high-frequency polysubstance use of crystal methamphetamine and heroin. In Vancouver, several profiles were associated with a greater likelihood of providing recent injection initiation assistance compared to the referent profile (low-frequency use of all drugs) in unadjusted and adjusted analyses, however, the inclusion of latent profile membership in the multivariable model did not significantly improve model fit.

DISCUSSION AND CONCLUSIONS

We identified commonalities and differences in polysubstance use patterns among people who inject drugs in three settings disproportionately impacted by injection drug use. Our results also suggest that other factors may be of greater priority when tailoring interventions to reduce the incidence of injection initiation. These findings can aid in efforts to identify and support specific higher-risk subpopulations of people who inject drugs.

Network-level HIV risk norms are associated with individual-level HIV risk and harm reduction behaviors among people who inject drugs: a latent profile analysis

The COVID-19 related U.S.-Mexico border-crossing restrictions disrupted social networks and HIV harm reduction services among people who inject drugs (PWID) in San Diego and Tijuana. We assessed associations of descriptive network norms on PWID's HIV vulnerability during this period. Between 10/2020 and 10/2021, 399 PWID completed a behavioral and egocentric questionnaire. We used Latent Profile Analysis to categorize PWID into network norm risk profiles based on proportions of their network (n = 924 drug use alters) who injected drugs and engaged in cross-border drug use (CBDU), among other vulnerabilities. We used logistic and linear regressions to assess network profile associations with individual-level index of HIV vulnerability and harm reduction behaviors. Fit indices specified a 4-latent profile solution of descriptive network risk norms: lower (n = 178), moderate with (n = 34) and without (n = 94) CBDU and obtainment, and higher (n = 93). Participants in higher risk profiles reported more HIV vulnerability behaviors and fewer harm reduction behaviors. PWID's gradient of HIV risk was associated with network norms, warranting intervention on high-vulnerability networks when services are limited.

HIV and Substance Use in Latin America: A Scoping Review

This scoping review aims to explore the interplay between substance use (SU) and HIV in Latin America (LA). Database searches yielded 3481 references; 196 were included. HIV prevalence among people who used substances (PWUS) ranged from 2.8–15.2%. SU definitions were variable throughout studies, and thus data were not easily comparable. In 2019, only 2% of new HIV infections were attributed to injection drug use (IDU) in LA. Factors associated with HIV among PWUS included being female, IDU and homelessness, and PWUS were likely to engage in risky sexual behaviors, start antiretroviral treatment late, have poor adherence, have treatment failure, be lost to follow-up, have comorbidities, and experience higher mortality rates and lower quality of life, as has been reported in PLWH with SU in other regions. Five intervention studies were identified, and only one was effective at reducing HIV incidence in PWUS. Interventions in other regions have varying success depending on context-specific characteristics, highlighting the need to conduct more research in the LA region. Though progress has been made in establishing SU as a major concern in people living with HIV (PLWH), much more is yet to be done to reduce the burden of HIV and SU in LA.

Impact of cumulative incarceration and the post-release period on syringe-sharing among people who inject drugs in Tijuana, Mexico: a longitudinal analysis

BACKGROUND AND AIMS

Syringe-sharing among people who inject drugs, which can occur during incarceration and post-release, has been linked with increased risk of blood-borne infections. We aimed to investigate the cumulative effect of repeated incarceration and the post-release period on receptive syringe-sharing.

DESIGN

Ongoing community-based cohort, recruited through targeted sampling between 2011 and 2012 with 6-month follow-ups.

SETTING

Tijuana, Mexico.

PARTICIPANTS

Sample of 185 participants (median age 35 years; 67% female) with no history of incarceration at study entry, followed to 2017.

MEASUREMENTS

Cumulative incarceration and post-release period were constructed from incarceration events reported in the past 6 months for each study visit. Receptive syringe-sharing in the past 6 months was assessed as a binary variable. We used logistic regression with generalized estimating equations to examine the association between cumulative incarceration events and the post-release period with receptive syringe-sharing over time. Missing data were handled through multiple imputation.

FINDINGS

At baseline, 65% of participants engaged in receptive syringe-sharing in the prior 6 months. At follow-up, 150 (81%) participants experienced a total of 358 incarceration events [median = 2, interquartile range (IQR) = 1-3]. The risk of receptive syringe-sharing increased with the number of repeated incarcerations. Compared with never incarcerated, those with one incarceration had 1.28 [95% confidence interval (CI) = 0.97-1.68] higher adjusted odds of syringe-sharing; two to three incarcerations, 1.42 (95% CI = 1.02-1.99) and more than three incarcerations, 2.10 (95% CI = 1.15-3.85). Participants released within the past 6 months had 1.53 (95% CI = 1.14-2.05) higher odds of sharing syringes compared with those never incarcerated. This post-release risk continued up to 1.5 years post-incarceration (adjusted odds ratio = 1.41, 95% CI = 1.04-1.91), but then waned.

CONCLUSIONS

A longitudinal community cohort study among people who inject drugs suggested that the effects of incarceration on increased injecting risk, measured through syringe-sharing, are cumulative and persist during the post-release period.

Risk of non-fatal overdose and polysubstance use in a longitudinal study with people who inject drugs in Tijuana, Mexico

INTRODUCTION

Among people who inject drugs (PWID), polysubstance use has been associated with fatal and non-fatal overdose (NFOD). However, the risk of overdose due to the cumulative number of various recently used drug types remains unexplored. We estimated the risk of NFOD for different polysubstance use categories among PWID in Tijuana, Mexico.

METHODS

Data came from 661 participants followed for 2 years in Proyecto El Cuete-IV, an ongoing prospective cohort of PWID. A multivariable Cox model was used to assess the cumulative impact of polysubstance use on the time to NFOD. We used the Cochran-Armitage test to evaluate a dose-response relationship between number of polysubstance use categories and NFOD.

RESULTS

We observed 115 NFOD among 1029.2 person-years of follow-up (incidence rate: 11.2 per 100 person-years; 95% confidence interval [CI] 9.3-13.3). Relative to those who used one drug class, the adjusted hazard ratio of NFOD for individuals reporting using two drug classes was 1.11 (95% CI 0.69-1.79), three drug classes was 2.00 (95% CI 1.16-3.44) and for those reporting three compared to two was 1.79 (95% CI 1.09-2.97). A significant Cochran-Armitage trend test (P < 0.001) suggested a dose-response relationship.

DISCUSSION AND CONCLUSIONS

Polysubstance use was associated with increased risk of NFOD with a dose-response relationship over 2 years. We identified a subgroup of PWID at high risk of NFOD who reported concurrent use of opioids, stimulants and benzodiazepines. Prioritising tailored harm reduction and overdose prevention interventions for PWID who use multiple substances in Tijuana is needed.

Polysubstance use in the U.S. opioid crisis

Interventions to address the U.S. opioid crisis primarily target opioid use, misuse, and addiction, but because the opioid crisis includes multiple substances, the opioid specificity of interventions may limit their ability to address the broader problem of polysubstance use. Overlap of opioids with other substances ranges from shifts among the substances used across the lifespan to simultaneous co-use of substances that span similar and disparate pharmacological categories. Evidence suggests that nonmedical opioid users quite commonly use other drugs, and this polysubstance use contributes to increasing morbidity and mortality. Reasons for adding other substances to opioids include enhancement of the high (additive or synergistic reward), compensation for undesired effects of one drug by taking another, compensation for negative internal states, or a common predisposition that is related to all substance consumption. But consumption of multiple substances may itself have unique effects. To achieve the maximum benefit, addressing the overlap of opioids with multiple other substances is needed across the spectrum of prevention and treatment interventions, overdose reversal, public health surveillance, and research. By addressing the multiple patterns of consumption and the reasons that people mix opioids with other substances, interventions and research may be enhanced.

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

INTRODUCTION AND AIMS

HIV and hepatitis C virus transmission among people who inject drugs (PWID) is fuelled by personal and environmental factors that vary by sex. We studied PWID in Mexico to identify sex differences in multilevel determinants of injection risk.

DESIGN AND METHODS

From 2011 to 2013, 734 PWID (female: 277, male: 457) were enrolled into an observational cohort study in Tijuana. Participants completed interviews on injection and sexual risks. Utilising baseline data, we conducted multiple generalised linear models stratified by sex to identify factors associated with injection risk scores (e.g. frequency of injection risk behaviours).

RESULTS

For both sexes, difficult access to sterile syringes was associated with elevated injection risk (b = 1.24, 95% confidence interval [CI] 1.16-1.33), using syringes from a safe source (e.g. needle exchange programs) was associated with lower injection risk (b = 0.87, 95% CI 0.82-0.94), and for every one-unit increase in safe injection self-efficacy we observed a 20% decrease in injection risk (b = 0.80, 95% CI 0.76-0.84). Females had a higher safe injection self-efficacy score compared to males (median 2.83, interquartile range 2.2-3 vs. median 2.83, interquartile range 2-3; P = 0.01). Among females, incarceration (b = 1.22, 95% CI 1.09-1.36) and police confiscation of syringes in the past 6 months (b = 1.16, 95% CI 1.01-1.33) were associated with elevated injection risk. Among males, sex work (b = 1.16, 95% CI 1.04-1.30) and polysubstance use in the past 6 months (b = 1.22, 95% CI 1.13-1.31) were associated with elevated injection risk.

DISCUSSION AND CONCLUSIONS

Interventions to reduce HIV and hepatitis C virus transmission among PWID in Tijuana should be sex-specific and consider multilevel determinants of injection risk to create safer drug use environments.

Identification of Typologies of Cocaine Use Based on Quantity, Frequency, and Duration of Use: A Latent Profile Analysis

OBJECTIVES

We identified the patterns of cocaine use during individuals' heaviest use period by considering quantity, frequency, and duration simultaneously and examined the correlates and risk profile for these patterns.

METHODS

Latent profile analysis was conducted among the 3117 individuals who reported lifetime use of cocaine in the National Epidemiologic Survey on Alcohol and Related Conditions-III (NESARC-III) with quantity, frequency, and duration used as indicators. Logistic regression analyses examined factors associated with subtype membership based on patterns of cocaine use and the relationships between these patterns and cocaine use disorder (CocUD) and its severity.

RESULTS

Four patterns were identified: a "low use" class (72.6%), a "moderate use" class (8.2%), a "daily use" class (17.9%), and a "very high quantity use" class (1.3%). Relative to non-Hispanic White and the "low use" class, non-Hispanic Black was associated with increased odds to be in the "moderate use" and "daily use" classes. Higher prevalence of smoking crack cocaine and poly-route use was observed among the "very high quantity use" class relative to other classes; increased risk of using other substances was associated with the "daily use" class. Higher levels of cocaine use were associated with higher risks of CocUD and worse severity compared to the "low use" class.

CONCLUSIONS

People who use cocaine are heterogeneous with different patterns of use and risks of CocUD. Reducing cocaine smoking and poly-route of use should be placed as the same priority as decreasing very high quantity of use in interventions.

Towards Targeted Interventions in Low- and Middle-Income Countries: Risk Profiles of People Who Inject Drugs in Haiphong (Vietnam)

People who inject drugs (PWID) are a dominant risk group afflicted by blood-borne viruses, mental health disorders, and social precariousness. Risk reduction interventions are administered to PWID regardless of their characteristics or specific risks. The objective of this cross-sectional analysis was to empirically identify profiles of PWID regarding their drug use, risk behaviors, and mental health in order to tailor adapted interventions taking into account limited access to comprehensive care in middle-income countries. PWID were recruited using respondent-driven sampling. PWID with urine testing positive for heroin or methamphetamine and manifesting recent skin injection marks were enrolled. Classification of participants was based on drug use, injection, risky sexual behavior, and mental health data. This was subjected to multiple correspondence analysis followed by hierarchical cluster analysis combined with K-means methodology. From October 2016 to January 2017, 1490 participants were recruited of which 1383 were eligible and enrolled. HCV prevalence was 70.5% and HIV prevalence 29.4%. The cluster analysis identified five distinct profiles: profile 1: recent injection practices and high alcohol consumption, profile 2: at-risk injection and sexual behaviors with precarious situations, profile 3: no sexual activity and older age, profile 4: frequent injections with high methamphetamine use, and profile 5: stable partnerships and less frequent injections. Our study has identified profiles of PWID at particularly high risks, and they should thus be targeted for interventions tailored to their specific risks.

Estimating the contribution of stimulant injection to HIV and HCV epidemics among people who inject drugs and implications for harm reduction: A modeling analysis

BACKGROUND

Stimulants, such as amphetamines and cocaine, are widely injected among people who inject drugs (PWID). Systematic reviews indicate stimulant injection is associated with HIV and HCV among PWID. Using these associations, we estimated the contribution of stimulant injection to HIV and HCV transmission among PWID.

METHODS

We modeled HIV and HCV transmission among PWID, incorporating excess injecting and sexual risk among PWID who inject stimulants. We simulated three illustrative settings with different stimulants injected, prevalence of stimulant injecting, and HIV/HCV epidemiology. We estimated one-year population attributable fractions of stimulant injection on new HIV and HCV infections, and impact of scaling up needle-syringe programs (NSP).

RESULTS

In low prevalence settings of stimulant injection (St. Petersburg-like, where 13 % inject amphetamine), 9% (2.5-97.5 % interval [95 %I]: 6-15 %) and 7% (95 %I 4-11 %) of incident HIV and HCV cases, respectively, could be associated with stimulant injection in the next year. With moderate stimulant injection (Montreal-like, where 34 % inject cocaine), 29 % (95 %I: 19-37 %) and 19 % (95 %I: 16-21 %) of incident HIV and HCV cases, respectively, could be associated with stimulant injection. In high-burden settings like Bangkok where 65 % inject methamphetamine, 23 % (95%I:10-34%) and 20 % (95%I: 9-27%) of incident HIV and HCV cases could be due to stimulant injection. High-coverage NSP (60 %) among PWID who inject stimulants could reduce HIV (by 22-65 %) and HCV incidence (by 7-11 %) in a decade.

DISCUSSION

Stimulant injection contributes substantially to HIV and HCV among PWID. NSP scale-up and development of novel interventions among PWID who inject stimulants are warranted.

Modelling integrated antiretroviral treatment and harm reduction services on HIV and overdose among people who inject drugs in Tijuana, Mexico

INTRODUCTION

The HIV epidemic in Tijuana, Mexico is concentrated in key populations, including people who inject drugs (PWID). However, HIV interventions among PWID are minimal, and federal funding was provided for compulsory abstinence programmes associated with HIV and overdose. Alternatively, opioid agonist therapy reduces overdose, reincarceration, HIV, while improving antiretroviral therapy (ART) outcomes. We assessed potential impact and synergies of scaled-up integrated ART and opioid agonist therapy, compared to scale-up of each separately, and potential harms of compulsory abstinence programmes on HIV and fatal overdose among PWID in Tijuana.

METHODS

We developed a dynamic model of HIV transmission and overdose among PWID in Tijuana. We simulated scale-up of opioid agonist therapy from zero to 40% coverage among PWID. We evaluated synergistic benefits of an integrated harm reduction and ART scale-up strategy (40% opioid agonist therapy coverage and 10-fold ART recruitment), compared to scale-up of each intervention alone or no scale-up of low coverage ART and no harm reduction). We additionally simulated compulsory abstinence programmes (associated with 14% higher risk of receptive syringe sharing and 76% higher odds of overdose) among PWID.

RESULTS

Without intervention, HIV incidence among PWID could increase from 0.72 per 100 person-years (PY) in 2020 to 0.92 per 100 PY in 2030. Over ten years, opioid agonist therapy scale-up could avert 31% (95% uncertainty interval (UI): 18%, 46%) and 22% (95% UI: 10%, 28%) new HIV infections and fatal overdoses, respectively, with the majority of HIV impact from the direct effect on HIV transmission due to low ART coverage. Integrating opioid agonist therapy and ART scale-up provided synergistic benefits, with opioid agonist therapy effects on ART recruitment/retention averting 9% more new infections compared to ART scale-up alone. The intervention strategy could avert 48% (95% UI: 26%, 68%) of new HIV infections and one-fifth of fatal overdoses over ten years. Conversely, compulsory abstinence programmes could increase HIV and overdoses.

CONCLUSIONS

Integrating ART with opioid agonist therapy could provide synergistic benefits and prevent HIV and overdoses among PWID in Tijuana, whereas compulsory abstinence programmes could cause harm. Policymakers should consider the benefits of integrating harm reduction and HIV services for PWID.

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.

Examining risk behavior and syringe coverage among people who inject drugs accessing a syringe services program: A latent class analysis

INTRODUCTION

Injection drug use (IDU) remains a significant public health problem. IDU has been associated closely with the opioid crisis; driving overdose, HIV, and Hepatitis C (HCV) infection nationwide. Syringe services programs (SSPs) remain pivotal evidence-based interventions to reduce harm and engage subgroups of people who inject drugs (PWID). This study aims to provide policy considerations from the IDEA SSP, the first legal SSP in the state of Florida.

METHODS

We performed a latent class analysis on patterns of substance use among participants (N = 982) newly enrolled in a syringe services program (SSP). Associations between classes of substance use and sociodemographic variables, risky injection and sex behaviors, HIV/HCV status and syringe coverage were analyzed using the R3STEP and BCH 3-step procedures in latent class regression.

RESULTS

We found a three-class solution: Heroin-Dominant class (73.9%), Methamphetamine-Dominant class (9.5%) and Heroin/Cocaine class (16.6%). Compared to Heroin-Dominant class, the Heroin/Cocaine class were more likely to report homelessness, sharing works, unprotected sex, public injection, and to be HCV positive. Compared to both Heroin-Dominant and Heroin/Cocaine classes, the Methamphetamine-Dominant class were more likely to be male, Hispanic, gay or bisexual orientation, HIV positive, to report unprotected sex and sex with PWID. In addition, the lowest and highest syringe coverage were among those in the Heroin/Cocaine and Methamphetamine-Dominant classes, respectively.

CONCLUSION

Existing interventions among this population to mitigate infectious disease risk, such as SSPs, can be a used to engage differing PWID populations. However, multi-component, targeted preventive interventions and need-based syringe distribution policies are required to further reduce HIV and HCV risk among various PWID populations.

A latent class analysis of drug and substance use patterns among patients treated in emergency departments for suspected drug overdose

INTRODUCTION

Polysubstance use and misuse can increase risks for nonfatal and fatal drug overdose. To categorize drugs used in combination in nonfatal overdoses, we analyzed data from emergency department (ED) overdose-related visits in 18 states funded by CDC's Enhanced State Opioid Overdose Surveillance (ESOOS) program.

METHODS

From 2017 to 2018, 120,706 ED visits included at least one hospital discharge code indicating acute drug poisoning for opioids, stimulants, hallucinogens, cannabis, anti-depressants, sedatives, alcohol, benzodiazepines, or other psychotropic drugs. Latent class analyses were conducted to determine the groupings of drug combinations in overdose visits.

RESULTS

Latent class analyses indicated a model of 5 classes - mostly heroin overdose (42.5% of visits); mostly non-heroin opioid overdose/use (27.3%); opioid, polysubstance (11.0%); female, younger (<25 years), other non-opioid drugs (10.5%); female, older (>55 years), benzodiazepine (8.0%). Findings indicated that heroin continues to be a large burden to EDs, yet EDs are also seeing overdose survivors with polydrug toxicity.

CONCLUSIONS

Medication-assisted treatment could be initiated in the emergency department following overdose for patients with opioid use disorder, and post-overdose protocols, such as naloxone provision and linkage to treatment and harm reduction services, have the potential to prevent future overdose for those at risk.

Polysubstance use in rural West Virginia: Associations between latent classes of drug use, overdose, and take-home naloxone

BACKGROUND

Rural communities in the United States have been disproportionately affected by the opioid crisis. Little research has explored the relationship between polysubstance use and overdose experiences among people who inject drugs (PWID) in rural communities. We sought to identify classes of polysubstance drug use among rural PWID and evaluate the associations between polysubstance drug use classes, recent overdose experiences, and receipt of take-home naloxone (THN).

METHODS

We surveyed 420 PWID (June-July 2018) who had injected drugs in the previous 6 months in Cabell County, West Virginia. Participants were recruited from the local syringe services program and through street-based recruitment. We conducted a latent class analysis using 9 measures of injection and non-injection drug use and tested for associations with having experienced an overdose in the past 6 months and having received THN in the past 6 months.

RESULTS

We identified four substance use classes in our sample: polydrug/polyroute use (35.0% of the sample), polyroute stimulant/injection opioid use (33.3%), polyroute stimulant use (20.3%), and injection opioid use (11.3%). Overall, 42.6% of the sample had experienced an overdose in the past 6 months. The classes differed in terms of overdose (χ=91.53, p<0.001), with the polydrug/polyroute use class having the highest probability of overdose and the polyroute stimulants class having the lowest. Only 46.5% of participants had received THN, and probabilities differed between classes (χ=21.93, p<0.001). The polyroute stimulants/injection opioid use and polydrug/polyroute use classes had the highest levels of THN receipt while the polyroute stimulants use class had the least.

CONCLUSION

Among rural PWID in West Virginia, polysubstance use was prevalent and associated with overdose and THN acquisition. These analyses demonstrate the importance of scaling up naloxone distribution in rural settings. Overdose prevention initiatives are reaching persons at high risk of overdose, but expansion of services is needed.

CAM Practices and Treatment Adherence Among Key Subpopulations of HIV+ Latinos Receiving Care in the San Diego-Tijuana Border Region: A Latent Class Analysis

Latinos living in the United States-Mexico border region bear a disproportionate HIV/AIDS burden compared to individuals living in the interior of both nations and face a constellation of barriers that determine their ability to access and adhere to HIV care. Use of complementary and alternative medicine (CAM) may be associated with suboptimal treatment adherence. Sociodemographic factors, health practices, and social determinants of health unique to the border region may further contribute to health disparities that undermine care engagement and continuity. Improved understanding of HIV-positive Latino subgroups and their risk profiles can lead to more effective, targeted clinical and public health interventions. We undertook this study to identify and characterize distinct classes of HIV-positive Latinos in the San Diego-Tijuana border region, differentiated by HIV and border-related factors, utilizing latent class analysis. We investigated relationships between class membership and CAM utilization and self-reported antiretroviral therapy (ART) adherence. Five distinct classes were identified with unique demographic, HIV risk, and border mobility profiles. CAM was recently used by nearly half of each class, though there were significant differences in the proportion of CAM use by class ranging from 44.4 to 90.9%. As well, all classes were currently receiving ART at similarly high rates and ART adherence outcomes were not significantly different based on class. Findings highlight the significant use of CAM by all HIV-positive Latinos in the border region and imply the need for a research framework which appropriately acknowledges the heterogeneous nature of this population, such as intersectionality. Further research is recommended into understanding how patients integrate CAM into HIV treatment and the risks and benefits of incorporating CAM into HIV treatment.

Types of Polydrug Use Among Spanish Students in Health Sciences

Polydrug use among university students may be a predictor for established patterns of multiple substance use and potentially entail long-term health problems. This study examined the types of polydrug use among Spanish students in health sciences. Undergraduate students (n = 968), aged 18-38 years (M = 21.09 years, SD = 4.10), completed the survey. A percentage of 44.3% of the participants were classified as polydrug users. Type A users (alcohol and cigarettes) made up 17.8% of the participants surveyed, whereas 20.1% were Type B (cannabis with cigarettes and/or alcohol), and a further 5.7% were Type C (cannabis with cigarettes and/or alcohol, plus at least another kind of illegal drug). Type A was the most common type among women, whereas Type C was the most common among men. Type B use was higher among women 18-19 years old than among women 25-29 years old, whereas there were no female Type C users younger than 20 years old. Weekend consumption was higher, than weekday consumption, across all polydrug user types and substances. These results suggest that the prevalence of polydrug use among Spanish students in health sciences was similar to students in other disciplines, with Type B as the most prevalent among healthcare and nonhealthcare students. Taking into account the differences based on gender, age, and time of consumption, a specific approach to the different typologies of polydrug users might be a vital step in the successful development of preventive interventions tailored to the changing reality of psychoactive substance use.

"Another Person Was Going to Do It": The Provision of Injection Drug Use Initiation Assistance in a High-Risk U.S.-Mexico Border Region

Background: Persons who inject drugs (PWID) play a key role in assisting others' initiation into injection drug use (IDU). We aimed to explore the pathways and socio-structural contexts for this phenomenon in Tijuana, Mexico, a border setting marked by a large PWID population with limited access to health and social services. Methods: Preventing Injecting by Modifying Existing Responses (PRIMER) is a multi-cohort study assessing socio-structural factors associated with PWID assisting others into initiating IDU. Semi-structured qualitative interviews in Tijuana included participants ≥18 years old, who reported IDU within the month prior to cohort enrollment and ever initiating others into IDU. Purposive sampling ensured a range of drug use experiences and behaviors related to injection initiation assistance. Thematic analysis was used to develop recurring and significant data categories. Results: Twenty-one participants were interviewed (8 women, 13 men). Broadly, participants considered public injection to increase curiosity about IDU. Many considered transitioning into IDU as inevitable. Emergent themes included providing assistance to mitigate overdose risk and to protect initiates from being taken advantage of by others. Participants described reluctance in engaging in this process. For some, access to resources (e.g., shared drugs or a monetary fee) was a motivator to initiate others. Conclusion: In Tijuana, public injection and a lack of harm reduction services are perceived to fuel the incidence of IDU initiation and to incentivize PWID to assist in injection initiation. IDU prevention efforts should address structural factors driving PWID participation in IDU initiation while including PWID in their development and implementation.

Increased non-fatal overdose risk associated with involuntary drug treatment in a longitudinal study with people who inject drugs

AIM

To assess the effect of involuntary drug treatment (IDT) on non-fatal overdose among people who inject drugs (PWID).

DESIGN

Longitudinal study.

SETTING

Tijuana, Mexico.

PARTICIPANTS

Baseline sample of 671 PWID included 258 (38.4%) women and 413 (61.6%) men.

MEASUREMENTS

Primary independent variables were reported recent (i.e. past 6 months) non-fatal overdose event (dependent variable) and IDT. Substance use the day of the non-fatal overdose was also examined.

FINDINGS

From 2011 to 2017, 213 participants (31.7%) reported a recent non-fatal overdose and 103 (15.4%) reported recent IDT. Heroin, in combination with methamphetamine and tranquilizers, were the drugs most reported at the day of the event. IDT significantly increased the odds of reporting a non-fatal overdose event [adjusted odds ratio (aOR) = 1.76; 95% confidence interval (CI) = 1.04-2.96]. Odds of non-fatal overdose also increased independently for each additional injection per day (aOR = 1.05; 95% CI = 1.02-1.08), recent tranquilizer use (aOR = 1.92; 95% CI = 1.41-2.61) and using hit doctors (aOR = 1.68; 95% CI = 1.29-2.18) and decreased with age (aOR = 0.97 per year, 95% CI = 0.95-0.99).

CONCLUSIONS

Recent involuntary drug treatment in Mexico is a risk factor for non-fatal drug overdose.

Cost of provision of opioid substitution therapy provision in Tijuana, Mexico

BACKGROUND

Mexico recently enacted drug policy reform to decriminalize possession of small amounts of illicit drugs and mandated that police refer identified substance users to drug treatment. However, the economic implications of drug treatment expansion are uncertain. We estimated the costs of opioid substitution therapy (OST) provision in Tijuana, Mexico, where opioid use and HIV are major public health concerns.

METHODS

We adopted an economic health care provider perspective and applied an ingredients-based micro-costing approach to quantify the average monthly cost of OST (methadone maintenance) provision at two providers (one private and one public) in Tijuana, Mexico. Costs were divided by type of input (capital, recurrent personnel and non-personnel). We defined "delivery cost" as all costs except for the methadone and compared total cost by type of methadone (powdered form or capsule). Cost data were obtained from interviews with senior staff and review of expenditure reports. Service provision data were obtained from activity logs and senior staff interviews. Outcomes were cost per OST contact and cost per person month of OST. We additionally collected information on patient charges for OST provision from published rates.

RESULTS

The total cost per OST contact at the private and public sites was $3.12 and $5.90, respectively, corresponding to $95 and $179 per person month of OST. The costs of methadone delivery per OST contact were similar at both sites ($2.78 private and $3.46 public). However, cost of the methadone itself varied substantially ($0.34 per 80 mg dose [powder] at the private site and $2.44 per dose [capsule] at the public site). Patients were charged $1.93-$2.66 per methadone dose.

CONCLUSIONS

The cost of OST provision in Mexico is consistent with other upper-middle income settings. However, evidenced-based (OST) drug treatment facilities in Mexico are still unaffordable to most people who inject drugs.

Non-injection Drug Use and Injection Initiation Assistance among People Who Inject Drugs in Tijuana, Mexico

Although most people who inject drugs (PWID) report receiving assistance during injection initiation events, little research has focused on risk factors among PWID for providing injection initiation assistance. We therefore sought to determine the influence of non-injection drug use among PWID on their risk to initiate others. We used generalized estimating equation (GEE) models on longitudinal data among a prospective cohort of PWID in Tijuana, Mexico (Proyecto El Cuete IV), while controlling for potential confounders. At baseline, 534 participants provided data on injection initiation assistance. Overall, 14% reported ever initiating others, with 4% reporting this behavior recently (i.e., in the past 6 months). In a multivariable GEE model, recent non-injection drug use was independently associated with providing injection initiation assistance (adjusted odds ratio [AOR] = 2.42, 95% confidence interval [CI] = 1.39-4.20). Further, in subanalyses examining specific drug types, recent non-injection use of cocaine (AOR = 9.31, 95% CI = 3.98-21.78), heroin (AOR = 4.00, 95% CI = 1.88-8.54), and methamphetamine (AOR = 2.03, 95% CI = 1.16-3.55) were all significantly associated with reporting providing injection initiation assistance. Our findings may have important implications for the development of interventional approaches to reduce injection initiation and related harms. Further research is needed to validate findings and inform future approaches to preventing entry into drug injecting.

Perceived Treatment Need and Latent Transitions in Heroin and Methamphetamine Polydrug Use among People who Inject Drugs in Tijuana, Mexico

People who inject drugs (PWID) in Tijuana, Mexico, use heroin and/or methamphetamine. While polydrug use is associated with HIV risk behavior, less is known about the stability of polydrug use patterns over time and how polydrug use is related to perceived treatment need. Within a cohort of PWID in Tijuana (N = 735) we sought to (1) characterize subgroups of polydrug and polyroute use from baseline to six months; (2) determine the probabilities of transitioning between subgroups; and (3) examine whether self-reported need for help for drug use modified these transition probabilities. Latent transition analysis (LTA) identified four latent statuses: heroin-only injection (38% at both baseline and follow-up); co-injection of heroin with methamphetamine (3% baseline, 15% follow-up); injection of heroin and methamphetamine (37% baseline, 32% follow-up); and polydrug and polyroute users who injected heroin and both smoked and injected methamphetamine (22% baseline, 14% follow-up). Heroin-only injectors had the highest probability of remaining in the same latent status at follow-up. The majority reported great or urgent need for treatment (51%) and these PWID had greater odds of transitioning to a higher-risk status at follow-up, emphasizing the need for evidence-based drug treatment options for PWID.

The levels of triglyceride and total cholesterol in methamphetamine dependence

The serum triglyceride (TG) and total cholesterol (TC) levels have been reported altered in the traditional drug-dependence (such as marijuana and heroin). However, studies assessing the relationships among serum TC, TG, and methamphetamine (MA)-dependence have not been described well. In this study, our aim is to explore the serum TG and TC levels in large sample of MA-dependent patients. A retrospective study was conducted in 938 MA-dependent patients who were recruited between February 2, 2008 and March 11, 2013, with social characteristics and drug-dependence history (duration of MA use, routes of drug administration, and daily dose were collected). Then, the serum levels of TC, TG, glucose (GLU), body mass index (BMI), and blood pressure were measured among the participants. Meanwhile, 985 age- and gender-matched healthy people in the physical examination center were selected as control group. Compared with the control group, significant decreases of TC, TG, GLU, and BMI were observed in MA-dependent patients (P < 0.05). Besides, we found that the daily dose of MA use was associated with TC (β = -0.079, P = 0.015) and the duration of MA use was independently related to BMI (β = -0.071, P = 0.031). This study demonstrated that the levels of TC, TG, GLU, and BMI factors altered in the MA-dependent patients. In addition, there is a negative association between MA dependence and TC and BMI.