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The validity of reporting willingness to use a supervised injecting facility on subsequent program use… DeBeck, Kora; Kerr, Thomas; Lai, Calvin; Buxton, Jane; Montaner, Julio; Wood, Evan Aug 11, 2011

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The validity of reporting willingness to use a supervisedinjecting facility on subsequent program use among people whouse injection drugsKora DeBeck, PhD1,2, Thomas Kerr, PhD1,2, Calvin Lai, MSc1, Jane Buxton, MD3, JulioMontaner, MD, DSc (hon), FRCPC, FCCP, FACP, FRSC, OBC1,2, and Evan Wood, MD,PhD1,21British Columbia Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada2Division of AIDS, Department of Medicine, University of British Columbia, Vancouver, BC,Canada3School of Population and Public Health, University of British Columbia, Vancouver, BC, CanadaAbstractBackground—Innovative health programs for injection drug users (IDUs), such as supervisedinjecting facilities (SIFs), are often preceded by evaluations of IDUs’ willingness to use theservice. The validity of these surveys has not been fully evaluated. We sought to determinewhether measures of willingness collected prior to the opening of a Canadian SIF accuratelypredicted subsequent use of the program.Methods—Data were derived from a prospective cohort of IDUs. The sample size for this studywas 640 IDUs. Using multivariate logistic regression, it was assessed if a history of reportingwillingness to use the program, were it available, was associated with subsequent use. In sub-analysis restricted to individuals who had a history of reported willingness, we used multivariatelongitudinal analysis to identify factors associated with not attending the SIF.Results—Among 442 IDUs, 72% of those who reported initial willingness to use a SIF laterattended the program, and a prior willingness to use a SIF significantly predicted later attendance(adjusted odds ratio = 1.67). In sub-analyses restricted to those who had a history of reportingwillingness to use the SIF, not using the program was predicted by not frequenting theneighborhood where the SIF was located.Conclusion—Our findings indicate that reported willingness measures collected from IDUsregarding potential SIF program participation prior to its opening independently predicted laterattendance even when variables that were likely determinants of willingness were adjusted for.These data suggest that willingness measures are reasonably valid tools for planning the deliveryof health services among IDU populations.Corresponding author: Evan Wood, British Columbia Centre for Excellence in HIV/AIDS, 608-1081 Burrard Street, Vancouver, BCV6Z 1Y6, Canada, Tel: (604) 806-9116, uhri-ew@cfenet.ubc.ca.Author contributions:KD, TK, JM, and EW were responsible for study design; CL conducted the statistical analyses; KD prepared the first draft of theanalysis; TK, JB, JM, and EW contributed to the main content and provided critical comments on the final draft. All authors approvedthe final manuscript.Declaration of InterestDr. Julio Montaner has received grants from, served as an ad hoc advisor to, or spoke at various events sponsored by Abbott, ArgosTherapeutics, Bioject Inc., Boehringer Ingelheim, Bristol-Myers Squibb (BMS), Gilead Sciences, GlaxoSmithKline, Hoffmann-LaRoche, Janssen-Ortho, Merck Frosst, Pfizer, Schering, Serono Inc., TheraTechnologies, Tibotec, and Trimeris. The authors declare noother competing interests.NIH Public AccessAuthor ManuscriptAm J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.Published in final edited form as:Am J Drug Alcohol Abuse. 2012 January ; 38(1): 55–62. doi:10.3109/00952990.2011.600389.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptKeywordsinjection drug use; supervised injection facilities; validity of willingness measuresINTRODUCTIONIllicit drug use continues to be associated with a broad range of health and social harms andthere is growing recognition that innovative interventions are needed to address theseproblems (1–4). However, illicit drug use, particularly injection drug use, is highlystigmatized and it can be difficult for public health programs to connect with and effectivelyserve this often hidden population (5–7). This poses unique challenges for public healthprogrammers, as it is often difficult to predict whether a specific program will be acceptedby drug-using communities (8–11).One strategy that has been employed to assess the level of acceptance of innovative healthprograms, such as supervised injection facilities (SIFs) where injection drug users (IDUs)can bring pre-obtained illicit drugs and inject under the supervision of a nurse, has been tosurvey the target population and measure their willingness to use the proposed service (12–14). Behavioral willingness is considered to be distinct from behavioral intention, aswillingness is typically conceived in relation to what an individual is willing to do whileintention reflects what an individual plans to do (15,16). Some studies report that comparedwith intention measures, willingness measures are actually better predictors of behaviors(16–19). Although willingness measures have been used to determine acceptance of saferSIFs in several settings including Vancouver, Montreal, San Francisco, London, Ireland,Melbourne, and Sydney (12,20–26), the validity of these surveys among illicit drug-usingpopulations has not been fully evaluated. To assess whether willingness measures may beeffective tools for planning the delivery of public health programs for IDU populations, wesought to determine whether measures of willingness collected prior to the opening of aCanadian SIF accurately predicted later use of the program.MethodsData for this study were obtained from the Vancouver Injection Drug Users Study (VIDUS),an open prospective cohort that began enrolling IDUs through street outreach and self-referral in May 1996. To be eligible, participants at recruitment must reside in the GreaterVancouver Regional District, have injected illicit drugs in the previous month, and bewilling and able to provide written informed consent. This study has been described in detailpreviously (27,28). In brief, at enrolment and on bi-annual basis, participants complete aninterviewer-administered questionnaire and, after an examination by a study nurse, provide ablood sample for serologic testing. At each study visit, participants are provided with astipend ($20 CDN) for their time. The study has received ethics approval from St. Paul’sHospital and the University of British Columbia’s Research Ethics Board.In the primary analysis, we assessed whether reports of willingness to use a SIF before theprogram opened were associated with subsequent self-reported attendance at the facilityafter it was established in the Downtown Eastside (DTES) of Vancouver in September 2003.Initial willingness measures were assessed during the pre-SIF period of December 2001 toMay 2003. A total of 640 individuals were seen for study follow-up during the pre-SIF studyperiod. Willingness was based on the question “If a supervised safe injection site wasavailable, would you use it?” “Yes” responses were compared with “no” responses, andindividuals who replied that they were “unsure” were assessed in sub-analyses. AttendanceDeBeck et al. Page 2Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptat the facility was measured during the post-SIF period of December 2003 to November2005 based on the question “Have you ever used the InSite SIS?”Our primary analysis sought to determine whether there was a significant relationshipbetween our main dependent variable of interest (attendance at the SIF) and our primaryindependent variable (prior report of willingness to attend a SIF). To consider thisassociation while evaluating potential confounders, we a priori selected a range of secondaryexplanatory independent variables hypothesized to be associated with both attendance andinitial willingness to attend based on previous research (12,20,29). Secondary explanatoryfactors included age (younger than 39 years of age vs. older); gender (female vs. male);unstable housing, defined as living in a single occupancy room in a hotel, a treatment orrecovery house, jail, shelter or hostel, or having no fixed address for the last 6 months (yesvs. no); frequent exposure to the DTES, which is Vancouver’s well-described drug useepicenter and where the Vancouver SIF is situated (20), defined as residing in or visiting theDTES at least 2–3 times per week (yes vs. no); daily cocaine injection (yes vs. no); dailyheroin injection (yes vs. no); daily crack cocaine smoking (yes vs. no); non-fatal overdose(yes vs. no); and using injection drugs in public locations, such as city streets, parks, andalleys (yes vs. no). All drug use and behavioral variables refer to the previous 6-monthperiod and were measured at participants first study visit during our study period.As a first step, we compared baseline characteristics stratified by attendance at theVancouver SIF. We used Pearson’s χ2-test for dichotomous variables and the Mann–Whitney test for continuous variables. We were primarily concerned with identifyingwhether there was an independent relationship between just two variables (attendance at theSIF and prior report of willingness to attend a SIF). To address this, we used a backwardselection process with automated procedures, previously described by Maldonado andGreenland (30) and Rothman and Greenland (31), which is specific to fitting multivariatemodels in these instances. Specifically, we began by including all variables in a fixed model.We subsequently generated a series of confounding models by removing secondaryvariables one at a time. For each of these models, we assessed the relative change in thecoefficient for our primary independent variable of interest (prior willingness to use a SIF).The secondary variable that resulted in the smallest absolute relative change in thecoefficient of “prior willingness to use a SIF” was then removed. This approach allowed usto identify the secondary variables that had the strongest influence on the coefficient for ourprimary variable of interest. Using this automated procedure, secondary variables continuedto be removed until the smallest relative change in the coefficient of “prior willingness touse a SIF” exceeded 5% of the value of the coefficient. The final model included priorwillingness to use a SIF and all remaining secondary explanatory variables.To further explore the relationship between initial willingness and later use of a SIF, weconducted a number of sub-analyses. First, among individuals who reported that they hadnot attended the SIF, we assessed rates of non-injection drug use in the past 6 months duringthe post-SIF period, as well as infrequent exposure to the neighborhood where thesupervised injection site was located. Infrequent exposure was defined as not residing in theDTES and visiting the neighborhood less than monthly. We then sought to identify factorsassociated with not attending the SIF among participants who initially reported willingnessto use the facility. Factors that we hypothesized might be associated with not attending theVancouver SIF included: age (younger than 39 years of age vs. older); gender (female vs.male); infrequent exposure to the DTES (yes vs. no); infrequent cocaine injection (< dailyvs. ≥ daily); infrequent heroin injection (< daily vs. ≥ daily); being recently incarcerated (yesvs. no); and recently being involved in any kind of addiction treatment program (yes vs. no).All variables, including our outcome of interest, refer to behaviors in the previous 6 months.DeBeck et al. Page 3Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptSince for this analysis we were interested in identifying multiple factors that might beassociated with not using the SIF, we did not use the previous model-building protocolwhich is designed to adjust for confounding and determine whether there is an independentrelationship between just two factors of interest. Another distinguishing feature of this sub-analysis was that it focused on the post-SIF follow-up period of 24 months, and we hadmultiple observations per person for factors potentially associated with not using the SIF aswell as serial measures for each subject. Therefore, to determine factors associated with ouroutcome of interest throughout the entire 24-month follow-up period we used generalizedestimating equations (GEE) for binary outcomes with logit link for the analysis of correlateddata (32). These methods provided standard errors adjusted by multiple observations perperson using an exchangeable correlation structure. With this approach, data from everyparticipant follow-up visit were considered in this analysis. Missing data were addressedthrough the GEE mechanism which uses the all available pairs method to encompass themissing data from dropouts or intermittent missing. All non-missing pairs of data are used inthe estimators of the working correlation parameters.As a first step, GEE univariate analyses were conducted to obtain unadjusted odds ratios(ORs) and 95% confidence intervals (CIs) for variables of interest. In order to adjust forpotential confounding, all variables that were p < .05 in GEE univariate analyses wereentered into a multivariate logistic GEE model. All statistical analyses were performed usingSAS software version 9.1 (SAS, Cary, NC, USA). All p-values are two sided.RESULTSIn the pre-SIF period 344 (54%) participants reported being willing to use a SIF, 256 (40%)reported being unwilling, and 40 (6%) were unsure (see Figure 1). Among the “unsure”group 11 (28%) were not seen for study follow-up during the post-SIF study period, and ofthe remaining 29 “unsure” individuals, 18 (62%)subsequently used the facility. Among the600 participants who reported either being willing or unwilling to use a SIF, 158 (70 and 88,respectively) were not seen for study follow-up during the post-SIF study period and weretherefore excluded from further analyses. Those lost to follow-up were significantly lesslikely to report being willing to use a SIF (p < .001). The remaining 442 participants wereincluded in our primary comparison of those that reported yes versus no willingness. Amongthe 274 participants within this group who reported being initially willing to use a SIF, 198(72%) later reported attending the SIF, while 91 (54%) of those who were initially unwillinglater reported attending the SIF. The characteristics of the study sample stratified byreported attendance at the SIF are presented in Table 1. The univariate analyses ofbehavioral and socio-demographic variables are also presented in Table 1. Initial willingnessto use a SIF was significantly associated with later use of the facility (OR = 2.20, 95% CI:1.47–3.30). The results of the final multivariate logistic regression are shown in Table 2.Our primary explanatory variable, initial willingness to use a SIF, remained independentlyassociated with attending the SIF (adjusted OR (AOR) = 1.67, 95% CI: 1.09–2.55). Unstablehousing (AOR = 1.54, 95% CI: 1.01–2.34) and using injection drugs in public were alsoindependently associated with using the SIF (AOR = 2.35, 95% CI: 1.46–3.77). In sub-analyses, we found that among participants who did not attend the SIF, 31 (19%) reported atsome point during the post-SIF study period that they had not injected drugs in the previous6 months. Similarly, during the same period and among the same group, 32 (21%)individuals reported infrequent exposure to the DTES.In the sub-analysis restricted to the 274 individuals who initially reported being willing touse a SIF (see Table 3), being younger than 39 years of age, infrequent exposure to theDTES, infrequent cocaine injection, infrequent heroin injection, and engagement in anyaddiction treatment program were significantly associated with not using the SIF inDeBeck et al. Page 4Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptunivariate GEE analyses. In multivariate GEE analyses, infrequent exposure to the DTES(AOR = 1.89, 95% CI: 1.31–2.71), infrequent cocaine injection (AOR = 1.54, 95% CI:1.13–2.09), and infrequent heroin injection (AOR = 2.37, 95% CI: 1.77–3.17) weresignificantly positively associated with not using the SIF, while being younger than 39 yearsof age (AOR = 0.03, 95% CI: 0.01–0.05) was significantly negatively associated with notusing the SIF.DISCUSSIONOur study found that initial willingness to use a SIF was independently associated withsubsequent attendance at Vancouver’s SIF, even after adjusting for other determinants ofwillingness. We also found that not actively injecting drugs and infrequent exposure to theneighborhood where Vancouver’s SIF is located were factors that appear to negativelyinfluence whether individuals use a SIF following a report of being willing to use theprogram before it opened.These findings are largely consistent with a broad literature suggesting that behavioralintention is a reasonable predictor of later action (16,33). Intention measures have beenfound to be correlated with health-related behaviors in a number of areas includingadolescent smoking, illicit drug use, and sexual health (15,17,34–37). More specifically,these findings support previous studies suggesting that willingness measures are generallygood predictors of future behaviors (16–19).While our study indicates that willingness predicts future SIF use, it is also noteworthy thatpersonal circumstances including cessation from injection drug use, lower intensity injectiondrug use, and infrequent exposure to the DTES appear to have an expected deterrent effecton SIF use. These effects are expected given that actively injecting drugs is a prerequisitefor using the SIF, and the SIF has been shown to attract high-intensity drug injectors (38).Being an infrequent visitor to the neighborhood where the SIF was established would alsobe expected to reduce the likelihood that an individual would use the facility. Indeed,previous studies indicate that travel time to the SIF from where the IDU resides andpurchases drugs is a significant barrier to using the injection facility (39). The associationbetween younger age and lower likelihood of using the SIF may reflect the demographiccharacter of the neighborhood where the SIF was established. Previous research in our studysetting suggests that street-involved youth who use drugs tend to spatially separatethemselves from Vancouver’s DTES neighborhood and prefer to congregate in theDowntown South area of the city (40). This distancing may partially explain why youngerage was associated with not using Vancouver’s injection site despite being initially willing.In addition to the factors identified in our analysis, there are a number of otherconsiderations that could influence whether or not an individual chooses to use a facility ofthis nature. For example, waiting times and operating regulations such as a ban on assistedinjections could present barriers to individuals suffering from drug withdrawal symptoms orwho do not have the ability to self-inject. This might hinder the ability of these individualsto use the facility despite an initial willingness or intention to use it. Clearly, situationalfactors are relevant in determining SIF utilization; however, we found that despite thesemultiple factors, willingness measures are meaningful indicators of later SIF use.These findings have implications for the validity of willingness studies that have beenconducted in other settings to assess the acceptability of establishing SIFs. For instance, awillingness study conducted among IDUs in San Francisco recently reported that 85% oflocal IDUs were willing to use a SIF (21). Our study suggests that policy planners in SanFrancisco can be confident that this measure is a good indicator of client uptake, should aSIF be established in that area.DeBeck et al. Page 5Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptOur findings are also relevant to the planning of other types of public health programs andservices for IDU populations as they suggest that willingness measures are relativelyaccurate markers of a population’s intention to use a particular service. We should note thatdirectly engaging with people who use drugs and assessing willingness prior to theestablishment of a health service or program are consistent with a growing recognition of theimportance of involving target populations in the planning and delivery of health and socialservices, particularly among vulnerable populations (6,41). Although assessing willingnessis not a substitute for meaningful involvement, we suggest it can be a useful first step inengaging a target population in service design and delivery.Our study has a number of potential limitations. First, our measures relied on self-reportwhich can be subject to socially desirable reporting and recall bias. Most importantly,socially desirable reporting could have inflated our measure of SIF attendance, given itswidespread support and acceptance among local drug users. While it would have beenfavorable to validate self-reported attendance against the database of registered clients of theSIF a number of data limitations prevented this. First, in an effort to build trust among localdrug users and establish a low threshold service, the SIF client registry was not fullyoperational until 6 months after the facility opened (42). Second, the opportunity to consentto linking VIDUS participants with the SIF client registry was only offered during specificstudy follow-up periods. As a result not all VIDUS participants in our study sample weregiven the option of consenting to this process. Given the significant data limitationsresulting from these factors, it was unfortunately not feasible to accurately validate self-reports with the SIF client registry.Another potential limitation of our study is the generalizability of our findings. The VIDUSis not a randomized sample of IDUs and may not be reflective of other drug userpopulations. It is, however, believed to be representative of IDUs in the community (43,44).CONCLUSIONSIn summary, we found that individuals who indicated that they were willing to use a SIFwere more likely to later attend the Vancouver SIF once it was opened, even after weadjusted for factors expected to be associated with willingness. These data suggest thatwillingness measures may be valid tools for planning the delivery of health services amongIDU populations and should be considered by future health program planners.AcknowledgmentsWe thank the study participants for their contribution to the research, as well as current and past researchers andstaff. We would specifically thank Deborah Graham, Tricia Collingham, Carmen Rock, Peter Vann, CaitlinJohnston, Steve Kain, Danny Kain, and Calvin Lai for their research and administrative assistance. The study wassupported by the US National Institutes of Health (R01DA011591 and R01DA021525) and the Canadian Institutesof Health Research (MOP–79297, RAA–79918). Thomas Kerr is supported by the Michael Smith Foundation forHealth Research and the Canadian Institutes of Health Research. Kora DeBeck is supported by a Michael SmithFoundation for Health Research Senior Graduate Trainee Award and a Canadian Institutes of Health ResearchDoctoral Research Award. 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[PubMed: 7641667]38. Wood E, Tyndall M, Li K, Lloyd-Smith E, Small W, Montaner J, Kerr T. Do supervised injectingfacilities attract higher-risk injection drug users? Am J Prev Med. 2005; 29(2):126–130. [PubMed:16005809]39. Petrar S, Kerr T, Tyndall MW, Zhang R, Montaner JS, Wood E. Injection drug user’s perceptionsregarding use of a medically supervised safer injecting facility. Addict Behav. 2007; 32(5):1088–1093. [PubMed: 16930849]40. Fast D, Shoveller J, Shannon K, Kerr T. Safety and danger in downtown Vancouver:Understandings of place among young people entrenched in an urban drug scene. Health Place.2010; 16(1):51–60. [PubMed: 19733496]41. Jürgens, R. Nothing about Us without Us: Greater, Meaningful Involvement of People Who UseIllegal Drugs: A Public Health, Ethical and Human Rights Imperative. Toronto, ON, Canada:Canadian HIV/AIDS Legal Network; 2005.42. Wood E, Kerr T, Lloyd-Smith E, Buchner C, Marsh D, Montaner J, Tyndall M. Methodology forevaluating Insite: Canada’s first medically supervised safer injection facility for injection drugusers. Harm Reduct J. 2004; 1(9):1–5. [PubMed: 15169546]DeBeck et al. Page 8Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscript43. Tyndall MW, Craib KJP, Currie S, Li K, O’Shaughnessy MV, Schechter MT. Impact of HIVinfection on mortality in a cohort of injection drug users. JAIDS. 2001; 28(4):351. [PubMed:11707672]44. DeBeck K, Kerr T, Li K, Fischer B, Buxton J, Montaner J, Wood E. Emergence of crack cocainesmoking as a risk factor for HIV seroconversion among injection drug users in Vancouver,Canada. CMAJ. 2009; 181(9):585–589. [PubMed: 19841052]DeBeck et al. Page 9Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptFIGURE 1.Study sample.Note: SIF, supervised injection facility.DeBeck et al. Page 10Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptDeBeck et al. Page 11TABLE 1Univariate analyses of study population stratified by attendance at Vancouver’s SIF (n = 442).Characteristic1Attended SIF UnivariateYes (n= 289), n (%) No (n= 153), n (%) OR (95% CI) p-ValuePrior willingness to use SIF Yes 198(69) 76(50) 2.20(1.47–3.30) <.001 No 91 (31) 77(50)Younger than 39 years of age2 Yes 160(55) 60 (39) 1.92(1.29–2.86) <.001 No 129(45) 93(61)Female gender Yes 122 (42) 64 (42) 1.02(0.68–1.51) .938 No 167(58) 89(58)Unstable housing2,3 Yes 162(56) 64 (42) 1.77(1.19–2.64) .005 No 127 (44) 89(58)Frequent exposure to DTES2 Yes 163(56) 77(50) 1.28(0.86–1.89) .223 No 126 (44) 76(50)Daily cocaine injection2 Yes 94 (33) 31 (20) 1.90(1.19–3.02) .007 No 195(67) 122(80)Daily heroin injection2 Yes 95 (33) 24 (16) 2.63(1.60–4.34) <.001 No 194(67) 129(84)Daily crack use2 Yes 153(53) 57 (37) 1.89(1.27–2.83) .002 No 136(47) 96(63)Overdose(non-fatal)2 Yes 21 (7) 1 (1) 11.91(1.59–89.42) 016 No 268(93) 152(99)Public injecting2 Yes 142(49) 36 (24) 3.14(2.02–4.87) <.001 No 147(51) 117(76)Notes: SIF, supervised injection facility; OR, odds ratio; CI, confidence interval; DTES, Downtown Eastside of Vancouver, which is theneighborhood where the SIF is located.1All explanatory variables measured at first study visit during study period.2Denotes activities or situations referring to previous 6 months.3Unstable housing is defined as living in a single occupancy room in a hotel, a treatment or recovery house, jail, shelter or hostel, or having nofixed address for the last 6 months.Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptDeBeck et al. Page 12TABLE 2Multivariate logistic regression analysis of factors associated with attending Vancouver’s SIF versus notattending the facility (n = 442).Characteristic1 Adjusted odds ratio (95% confidence interval) p-ValuePrior willingness to use SIF Yes versus no 1.67 (1.09–2.55) .019Unstable housing2,3 Yes versus no 1.54 (1.01–2.34) .044Daily cocaine injection2 Yes versus no 1.52 (0.93–2.48) .095Daily heroin injection2 Yes versus no 1.63 (0.95–2.81) .076Public injecting2 Yes versus no 2.35 (1.46–3.77) <.001Notes: Overdose was not considered in this model due to low-frequency counts. SIF, supervised injection facility.1All explanatory variables were measured at first study visit during study period.2Denotes activities or situations referring to previous 6 months.3Unstable housing is defined as living in a single occupancy room in a hotel, a treatment or recovery house, jail, shelter or hostel, or having nofixed address for the last 6 months.Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptDeBeck et al. Page 13TABLE 3GEE analysis of factors associated with not using the SIF in the last 6 months (n = 76) versus using the facilityamong those who initially reported being willing to use an injection site (n = 274)Characteristic1Univariate MultivariateOR(95% CI) p-Value AOR(95% CI) p-ValueYounger than 39 years of age Yes versus no 1.65(1.18–2.29) .003 1.68(1.21–2.34) .002Gender Female versus male 1.09(0.75–1.58) .660Infrequent exposure to DTES2 Yes versus no 1.93(1.38–2.71) <.001 1.86(1.30–2.66) <.001Infrequent cocaine injection2 < daily versus > daily 1.82(1.36–2.44) <.001 1.52(1.12–2.06) .007Infrequent heroin injection2 < daily versus > daily 2.80(2.11–3.71) <.001 2.46(1.84–3.28) <.001Incarceration2 Yes versus no 0.78(0.59–1.09) .141Any addiction treatment2 Yes versus no 1.42(1.05–1.93) .024 1.23(0.90–1.68) .185Notes: GEE, generalized estimating equations; SIF, supervised injection facility; OR, odds ratio; CI, confidence interval; AOR, adjusted odds ratio;DTES, Downtown Eastside of Vancouver, which is the neighborhood where the SIF is located, infrequent exposure defined as being in theneighborhood less than 2–3 times per week.1Variable measures collected between December 2003 and November 2005.2Denotes activities or situations referring to previous 6 months.Am J Drug Alcohol Abuse. Author manuscript; available in PMC 2013 August 01.


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