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Homelessness independently predicts injection drug use initiation among street-involved youth in a Canadian… Feng, Cindy X.; DeBeck, Kora; Kerr, Thomas; Mathias, Steve; Montaner, Julio; Wood, Evan Apr 1, 2013

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Homelessness Independently Predicts Injection Drug UseInitiation among Street-involved Youth in a Canadian settingCindy Feng1, Kora DeBeck1,2, Thomas Kerr1,2, Steve Mathias3, Julio Montaner1,2, and EvanWood1,21British Columbia Centre for Excellence in HIV/AIDS, St. Paul’s Hospital2Department of Medicine, University of British Columbia3Department of Psychiatry, University of British ColumbiaAbstractPurpose—This longitudinal study examines the association between homelessness and injectiondrug use initiation among a cohort of street-involved youth in a setting of high prevalence crystalmethamphetamine use.Methods—Data were derived from the At-Risk Youth Study, a prospective cohort of street-involved youth aged 14 to 26 recruited between September 2005 and November 2011. Coxproportional hazards regression was used to identify factors independently associated with time toinjection initiation.Results—Among 422 street-youth who had never injected at baseline, 77 injection initiationevents were observed during follow-up. Homelessness was independently associated withinjection initiation in multivariate Cox regression (Relative Hazard: 1.80 [95% CI: 1.13–2.87])after adjusting for crystal methamphetamine use and other potential confounders.Conclusions—These findings highlight that homelessness is a key risk factor for injectioninitiation among street-involved youth. Supportive housing interventions for street-youth may helpprevent injection drug use initiation among this high-risk population.KeywordsYouth; injection drug use; initiation; homelessness© 2012 Society for Adolescent Medicine. Published by Elsevier Inc. All rights reserved.Send correspondence to: Evan Wood, MD, PhD, Professor of Medicine, University of British Columbia, BC Centre for Excellence inHIV/AIDS, 608 - 1081 Burrard Street, Vancouver BC V6Z1Y6, Canada, Tel:(604)806-9116, Fax: (604)806-9044, urhi-ew@cfenet.ubc.ca.Competing Interests:CF, KD, TK, SM, and EW have no conflicts of interest to declare. JM has received grants from, served as an ad hoc advisor to, orspoke at various events sponsored by; Abbott, Argos Therapeutics, Bioject Inc, Boehringer Ingelheim, BMS, Gilead Sciences,GlaxoSmithKline, Hoffmann-La Roche, Janssen-Ortho, Merck Frosst, Pfizer, Schering, Serono Inc, Thera Technologies, Tibotec,Trimeris.Implications and Contribution:This longitudinal study investigates the association between homelessness and time to first injection drug use among a cohort ofstreet-involved youth. Findings indicate that homelessness is independently associated with injection initiation, which suggests thataddressing the housing needs of street-involved youth may help prevent injection initiation.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to ourcustomers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review ofthe resulting proof before it is published in its final citable form. Please note that during the production process errors may bediscovered which could affect the content, and all legal disclaimers that apply to the journal pertain.NIH Public AccessAuthor ManuscriptJ Adolesc Health. Author manuscript; available in PMC 2014 April 01.Published in final edited form as:J Adolesc Health. 2013 April ; 52(4): 499–501. doi:10.1016/j.jadohealth.2012.07.011.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptIntroductionStreet-involved youth experience numerous health and social challenges, and frequentlyreport multiple barriers to obtaining housing [1]. Indeed, homelessness among street-involved youth is common and current data indicate the trend is increasing [2]. Injectiondrug use among this population is also prevalent and new injectors are often more likely toengage in risky injection practices that increase transmission of HIV and other infectiousdiseases [3]. Furthermore, in many urban settings, use of crystal methamphetamine isgrowing and may be contributing to increased initiation into injection drug use and relatedrisk behaviors [4].In the context of crystal methamphetamine epidemics characterized by alarmingly high ratesof syringe sharing and HIV risk behavior [3, 4], the potential relationship betweenhomelessness and injection initiation is of international interest given that risks related tohomelessness may be highly amenable to intervention. The present study was conducted toexamine if homelessness remains a key risk factor for injection initiation among apopulation of street-involved youth with a high prevalence of crystal methamphetamine use.MethodsData were derived from the At-Risk Youth Study (ARYS), which is a prospective cohort ofstreet-involved youth in Vancouver, Canada. Street-involved youth are defined as youth age14–26, who are absolutely, periodically or temporally at risk of being homeless, and spend asubstantial amount of time on the street or heavily involved in the street economy [4]. TheARYS cohort has been described in detail previously [3,4]. In brief, eligibility criteria forthe study included age 14–26 years and use of illicit drugs other than marijuana in the past30 days. Interviews were conducted from September 2005 to November 2011. The study hasbeen ethically approved.The primary outcome was time to injection initiation and the primary independent variableof interest was homelessness in the last six months, defined as sleeping on the street orhaving no fixed address. To adjust for variables that might confound the relationshipbetween injection initiation and homelessness, we examined the following covariates:gender (male vs. female), age (per year increase), ethnicity (Caucasian vs. other), dailyconsumption of alcohol, Marijuana use, non-injection cocaine use, crack cocaine smoking,non-injection crystal methamphetamine use, and non-injection heroin use (yes vs. no for allsubstance use variables). Substance use variables, as well as homelessness, refer tosituations and behaviors over the previous six months and were treated as time-updatedcovariates on the basis of semi annual follow-up data. In addition, substance use variableswere lagged to the previous available observation to protect against reverse causality.The cumulative hazard of injection initiation was calculated for youth who were and werenot homeless during follow-up using Kaplan-Meier methods. Cox regression was then usedto calculate unadjusted and adjusted relative hazards and 95% confidence intervals. Todetermine whether homelessness was independently associated with injection initiationwhile adjusting for the effect of crystal methamphetamine use, we fit a series of confoundingmodels including homelessness and crystal methamphetamine use and all secondaryvariables. In a stepwise manner, we remove all secondary variables that did not change thecoefficient for the effect of homelessness on injection initiation by at least 5%. Remainingvariables were considered confounders and were included in the final multivariate analysis.All statistical analyses were performed using SAS software version 9.2.Feng et al. Page 2J Adolesc Health. Author manuscript; available in PMC 2014 April 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptResultsOf the 422 participants that met the inclusion criterion, 133 (32%) were female, and 148(35%) reported non-injection methamphetamine use at baseline. Over study follow-up, 77(18%) injection initiation events were observed. Baseline characteristic stratified byinjection initiation are provided in Table 1. The Kaplan-Meier estimates of the cumulativehazard of injection initiation stratified by homelessness are shown in Figure 1. As shown,homeless participants demonstrate significantly higher risk of injection initiation (p =0.013). The cumulative incidence of injection initiation among homeless participantsreached 32.8% over study follow-up compared to 15.8% among those who were nothomeless. Table 1 also shows the unadjusted and adjusted relative hazards of injectioninitiation. In multivariate Cox regression analyses, homelessness remains independentlyassociated with time injection initiation (adjusted relative hazards =1.80, 95% ConfidenceInterval: 1.13–2.87), after adjusting for the effect of crystal methamphetamine use.DiscussionIn our study, homelessness was independently associated with injection initiation afteradjustment for various socio-demographic factors and substance use behaviors includingcrystal methamphetamine use. These findings suggest that homelessness may increasevulnerability to injection initiation.In this study, age and gender were not significantly associated with injection initiation,whereas circumstances of injection initiation and factors associated with initiation have beenfound to vary by gender and age in earlier studies [5, 6]. Future studies should furtherexamine these issues.Overall our findings indicate that addressing the housing needs of street-involved youth mayhelp prevent injection initiation. Given the documented difficulties that street-involvedyouth face obtaining housing [1], increasing the supply of youth focused housing is one step.However, it is critical that housing models be closely monitored and evaluated [7, 8].Furthermore, identifying and addressing risk factors for homelessness among street-involvedyouth should be another priority. High intensity drug use, mental illness and inability toaccess mental health and addiction treatment have been linked to youth homelessness in paststudies and intervention studies require further attention [9, 10]. It is also important tohighlight that reducing youth homelessness in isolation will not address the complexdeterminants of injection initiation and evidence-based approaches are urgently required.This study has several limitations. First, our sample is not a random sample and thus maynot be generalizable. Second, our behavioral variables are based on self-report, and thereforemay be subject to recall bias and socially desirable reporting. Third, as with any non-randomized study, the relationship between homelessness and injection initiation could beinfluenced by confounders not measured by the study instrument.In summary, our findings highlight that homelessness is a key risk factor for injectioninitiation even after adjusting for other competing factors including crystalmethamphetamine use. These findings suggest that supportive housing interventions incombination with other youth specific programs may help prevent injection initiation amongthis high-risk population.AcknowledgmentsThe authors thank the study participants for their contribution to the research, as well as current and pastresearchers and staff. We would specifically like to thank Deborah Graham, Peter Vann, Caitlin Johnston, SteveFeng et al. Page 3J Adolesc Health. Author manuscript; available in PMC 2014 April 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptKain, and Calvin Lai for their research and administrative assistance. The study was supported by the US NationalInstitutes of Health (R01DA028532) and the Canadian Institutes of Health Research (MOP–102742). Kora DeBeckis supported by the Canadian Institutes of Health Research. Thomas Kerr is supported by the Michael SmithFoundation for Health Research. Julio Montaner has received an Avant-Garde award (DP1DA026182) from theNational Institute of Drug Abuse, US National Institutes of Health. Funding sources had no further role in studydesign; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submitthe paper for publication. This research was undertaken, in part, thanks to funding from the Canada Research Chairsprogram through a Tier 1 Canada Research Chair in Inner City Medicine which supports Dr Evan Wood.References1. Krüsi A, Fast D, Small W, Wood E, Kerr T. Social and structural barriers to housing among street-involved youth who use illicit drugs. Health Soc Care Community. 2010; 18(3):282–288. [PubMed:20102394]2. Kulik DM, Gaetz S, Crowe C, Ford-Jones E. Homeless youth’s overwhelming health burden: Areview of the literature. Paediatr Child Health. 2011; 16(6):43–47.3. Lloyd-Smith E, Kerr T, Zhang R, Montaner JSG, Wood E. High prevalence of syringe sharingamong street involved youth. Addict Res Theory. 2008; 16(4):353–358.4. Wood E, Stoltz JA, Montaner JS, Kerr T. Evaluating methamphetamine use and risks of injectioninitiation among street youth: The ARYS study. Harm Reduct J. 2006; 3(18)5. Roy é, Haley N, Leclerc P, Cédras L, Blais L, Boivin JF. Drug injection among street youths inMontréal: predictors of initiation. J Adolesc Health. 2003; 80(1):92–105.6. Doherty MC, Garfein RS, Monterroso E, Latkin C, Vlahov D. Gender differences in the initiation ofinjection drug use among young adults. J Adolesc Health. 2000; 77(3):396–414.7. Briggs D, Rhodes T, Marks D, Kimber J, Holloway G, Jones S. Injecting drug use and unstablehousing: Scope for structural interventions in harm reduction. Drugs (Abingdon Engl). 2009;16:436–450.8. Wadd S, Hutchinson S, Taylor A, Ahmed S, Goldberg DJ. High-risk injecting behaviour in hostelaccommodation for the homeless in Glasgow 2001–2002: A study combining quantitative andqualitative methodology. J Subst Use. 2006; 11(5):333–341.9. Rachlis B, Wood E, Zhang R, Montaner JS, Kerr T. High rates of homelessness among a cohort ofstreet-involved youth. Health Place. 2009; 15(1):10–17. [PubMed: 18358759]10. Hadland SE, Kerr T, Li K, Montaner JS, Wood E. Access to drug and alcohol treatment among acohort of street-involved youth. Drug Alcohol Depend. 2009; 101(1–2):1–7. [PubMed: 19081203]Feng et al. Page 4J Adolesc Health. Author manuscript; available in PMC 2014 April 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptFigure 1.Time to initiation of injection drug use among a cohort of street-involved youth inVancouver stratified by homelessness (n=422).Feng et al. Page 5J Adolesc Health. Author manuscript; available in PMC 2014 April 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptFeng et al. Page 6Table 1Baseline characteristics of street-involved youth who did and who did not initiate injection drug use and Univariate and Multivariate Cox regressionanalysis of factors associated with injection drug use initiation among street-involved youth in Vancouver (n = 422).CharacteristicBaseline characteristicsUnivariate and Multivariate Cox regression analysisInjection initiationUnadjusted HR† (95% CI)p-valueAdjusted HR† (95% CI)p-valueYes (n=77) n (%)No (n=345) n (%)Age21.3 (19.6, 22.5)21.6 (19.6, 23.3)0.96 (0.88 – 1.04)0.297 Per year olderCaucasian Yes54 (70.1)204 (59.1)1.50 (0.92 – 2.44)0.104 No23 (29.9)141 (40.9)Male Yes54 (70.1)235 (68.1)1.02 (0.63 – 1.67)0.920 No23 (29.9)110 (31.9)Homeless Yes57 (74.0)239 (69.3)1.80 (1.13 – 2.88)0.0131.80 (1.13 – 2.87)0.014 No20 (26.0)106 (30.7)Non-Injection Crystal Meth Use* Yes41 (53.2)107 (31.0)1.83 (1.16 – 2.87)0.0091.82 (1.16 – 2.85)0.010 No36 (46.8)238 (69.0)Non-Injection Cocaine Use* Yes31 (40.3)175 (50.7)0.99 (0.62 – 1.57)0.476 No46 (59.7)170 (49.3)Crack Cocaine Smoking* Yes52 (67.5)184 (53.3)1.38 (0.88 – 2.18)0.164 No25 (32.5)161 (46.7)Non-Injection Heroin Use* Yes18 (23.4%)48 (13.9)1.83 (1.06 – 3.14)0.029 No59 (76.6%)297 (86.1)J Adolesc Health. Author manuscript; available in PMC 2014 April 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptFeng et al. Page 7CharacteristicBaseline characteristicsUnivariate and Multivariate Cox regression analysisInjection initiationUnadjusted HR† (95% CI)p-valueAdjusted HR† (95% CI)p-valueYes (n=77) n (%)No (n=345) n (%)Marijuana Use* Yes64 (83.1)316 (91.6)0.87 (0.47 – 1.61)0.653 No13 (16.9)29 (8.4)Daily Alcohol Use* Yes14 (18.2)59 (17.1)0.99 (0.55 – 1.80)0.982 No63 (81.8)286 (82.9)*refers to the activities lagged to the pervious available follow-up† HR=Hazard RatioJ Adolesc Health. Author manuscript; available in PMC 2014 April 01.

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