Involvement of people who inject drugs in injection initiation events: a cross-sectional analysis identifying similarities and differences across three North American settings

Abstract

ObjectivesPeople who inject drugs (PWID) play an integral role in facilitating the entry of others into injection drug use (IDU). We sought to assess factors influencing PWID in providing IDU initiation assistance across three distinct North American settings and to generate pooled measures of risk.DesignWe employed data from three PWID cohort studies participating in PReventing Injecting by Modifying Existing Responses (PRIMER), for this cross-sectional analysis.SettingTijuana, Mexico; San Diego, USA; Vancouver, Canada.ParticipantsA total of 2944 participants were included in this study (Tijuana: n=766, San Diego: n=353, Vancouver: n=1825).MeasurementsThe outcome was defined as recently (ie, past 6 months) assisting in an IDU initiation event. Independent variables of interest were identified from previous PRIMER analyses. Site-specific multiple modified Poisson regressions were fit. Pooled relative risks (pRR) were calculated and heterogeneity across sites was assessed via linear random effects models.ResultsEvidence across all three sites indicated that having a history of providing IDU initiation assistance (pRR: 4.83, 95% CI: 3.49 to 6.66) and recently being stopped by law enforcement (pRR: 1.49, 95% CI: 1.07 to 2.07) were associated with a higher risk of providing assistance with IDU initiation; while recent opioid agonist treatment (OAT) enrolment (pRR: 0.64, 95% CI: 0.43 to 0.96) and no recent IDU (pRR: 0.21, 95% CI: 0.07 to 0.64) were associated with a lower risk. We identified substantial differences across site in the association of age (I2: 52%), recent housing insecurity (I2: 39%) and recent non-injection heroin use (I2: 78%).ConclusionWe identified common and site-specific factors related to PWID’s risk of assisting in IDU initiation events. Individuals reporting a history of assisting IDU initiations, being recently stopped by law enforcement, and recently injecting methamphetamine/speedball were more likely to have recently assisted an IDU initiation. Whereas those who reported not recently engaging in IDU and those recently enrolled in OAT were less likely to have done so. Interventions and harm reduction strategies aimed at reducing the harms of IDU should incorporate context-specific approaches to reduce the initiation of IDU.

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

“…The extent of influence of these contextual factors differ across each setting and was selected accordingly [34]. In the Vancouver model, this included age, gender, housing status, public injecting, duration of injecting career and recent law enforcement interaction [17,19,[33][34][35][36][37]. The Tijuana model included age, gender, housing status, duration of injection career and recent law enforcement interaction [17,19,[33][34][35][36][37].…”

“…In the Vancouver model, this included age, gender, housing status, public injecting, duration of injecting career and recent law enforcement interaction [17,19,[33][34][35][36][37]. The Tijuana model included age, gender, housing status, duration of injection career and recent law enforcement interaction [17,19,[33][34][35][36][37]. The San Diego model included age, gender and housing status as covariates interaction [33,34,36,37].…”

“…Covariates included in the analyses were selected based on a priori identification of an association with increasing injection frequency and/or injection initiation assistance provision, as described in the literature. The extent of influence of these contextual factors differ across each setting and was selected accordingly [34]. In the Vancouver model, this included age, gender, housing status, public injecting, duration of injecting career and recent law enforcement interaction [17,19,[33][34][35][36][37].…”

“…The Tijuana model included age, gender, housing status, duration of injection career and recent law enforcement interaction [17,19,[33][34][35][36][37]. The San Diego model included age, gender and housing status as covariates interaction [33,34,36,37]. The Wald chi-square test was used to assess the overall impact of LPA classes on the fit of each multivariable model.…”