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Risky and rushed public crack cocaine smoking : the potential for supervised inhalation facilities Voon, Pauline; Ti, Lianping; Dong, Huiru; Milloy, M-J; Wood, Evan; Kerr, Thomas; Hayashi, Kanna Jun 16, 2016

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RESEARCH ARTICLE Open AccessRisky and rushed public crack cocainesmoking: the potential for supervisedinhalation facilitiesPauline Voon1,2, Lianping Ti1,3, Huiru Dong1, M-J Milloy1,3, Evan Wood1,3, Thomas Kerr1,3 and Kanna Hayashi1,3*AbstractBackground: Despite the multitude of public health and community harms associated with crack cocaine use,little is known about factors associated with smoking crack in public and related risks such as rushed publiccrack smoking.Methods: Data were derived from two prospective cohort studies of people who use illicit drugs in Vancouver,Canada between 2010 and 2014. Multivariable generalized estimating equations were used to identify theprevalence and correlates of public crack smoking and rushed public crack smoking.Results: In total, 1085 participants who had smoked crack in the prior six months were eligible for the analysis, ofwhich 379 (34.9 %) reported always or usually smoking crack in public in the previous six months at some pointduring the study period. Factors positively and independently associated with public crack smoking includedpublic injection drug use (adjusted odds ratio [AOR]: 5.42, 95 % confidence interval [CI]: 3.76-7.82), homelessness(AOR: 3.48, 95 % CI: 2.77-4.36), at least daily crack use (AOR: 2.69, 95 % CI: 2.19-3.31), crack pipe sharing (AOR: 1.98,95 % CI: 1.60-2.46), drug dealing (AOR: 1.59, 95 % CI: 1.30-1.94), recent incarceration (AOR: 1.47, 95 % CI: 1.09-1.98),noticing police presence when buying or using drugs (AOR: 1.30, 95 % CI: 1.06-1.60), and younger age (AOR: 1.03,95 % CI: 1.01-1.04). Rushed public crack smoking, which was reported by 216 (28.8 %) of 751 participants who hadsmoked crack in public at least once during the study period, was positively and independently associated withhomelessness (AOR: 2.61, 95 % CI: 1.96-3.49), at least daily crack use (AOR: 1.48, 95 % CI: 1.11-1.98), crack pipesharing (AOR: 1.44, 95 % CI: 1.10-1.89), drug dealing (AOR: 1.39, 95 % CI: 1.04-1.86), and younger age (AOR: 1.02,95 % CI: 1.01-1.04).Conclusions: A high prevalence of public crack smoking and rushed public crack smoking was observed inthis setting. These findings point to the need for implementing and evaluating evidence-based public healthinterventions, such as supervised inhalation facilities, to reduce the risks and harms associated with smoking crackin public.Keywords: Crack, Cocaine, Public drug use, Rushed drug use, Supervised inhalation, Supervised consumption,Crack pipe distribution, Intravenous, Injection, Harm reduction* Correspondence: khayashi@cfenet.ubc.ca1Urban Health Research Initiative, British Columbia Centre for Excellence inHIV/AIDS, St. Paul’s Hospital, 608-1080 Burrard Street, Vancouver, BC V6Z 1Y6,Canada3Department of Medicine, University of British Columbia, St. Paul’s Hospital,608-1081 Burrard Street, Vancouver, BC V6Z 1Y6, CanadaFull list of author information is available at the end of the article© 2016 Voon et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Voon et al. BMC Public Health  (2016) 16:476 DOI 10.1186/s12889-016-3137-3BackgroundIn recent years, increases in crack cocaine use in manyNorth American settings have contributed to a “neglectedepidemic” in which crack cocaine has remained amongthe most prevalent and easily obtainable illicit drugs[1–3]. National population-level surveys estimate thatpast-year crack cocaine use is prevalent in approximately1.1 % and 0.3 % of the general adult populations in Canadaand the United States, respectively [4, 5]. A recent multi-criteria decision analysis performed by the IndependentScientific Committee on Drugs found that crack cocaine(herein referred to as “crack”) is among the top three illicitdrugs that are most harmful to individual users and toothers, due to its potential for causing substantial physical,psychological, and social harms [6]. Specifically, individ-uals who use crack have been found to have elevated riskof HIV, hepatitis C virus (HCV), tuberculosis, herpes zos-ter, and other infectious pathogens secondary to sores,burns, or cuts, either from shared crack pipes or from in-creased prevalence of sexual risk behaviors [7–14]. Add-itionally, crack use has been found to be associated withpolysubstance use, comorbid mental illness, incarceration,and other health and social-structural problems, yet re-search indicates that individuals who use crack may beless likely to access health and social services [3, 15–17].Crack is often smoked in public settings, which maycontribute to public health risks such as hazardousdebris from crack smoking paraphernalia potentiallycontaminated with infectious pathogens (e.g., from glasscrack pipes), as well as crack-related street disorder suchas public intoxication, dealing drugs in public, or relatedviolence [18–20]. To date, much of the literature onpublic drug use has focused on the use of injectiondrugs in public and associated risks. Specifically, publicinjecting has been found to be associated with greaterodds of injection-related risk behaviours (e.g., sharingused injection equipment, not cooking or filtering drugsprior to injecting), HIV and HCV transmission, and poorhealth and social status (e.g., more severe drug depend-ency, social isolation, and unstable lifestyles) [21–23].However, little is known about risks associated with theuse of non-injection drugs in public settings—particularlycrack.Furthermore, there is a dearth of research on factorsassociated with the use of non-injection drugs whilerushed. Here again, much of the literature has concen-trated on rushed injection drug use, which is oftenprompted by fear of police arrest or street violence, andwhich frequently involves risky injection behaviors (e.g.,jabbing at veins, not testing the strength of drugs beforeinjecting, re-using injecting equipment) that may lead tovein trauma, abscesses, overdose, bacterial infections, orinfectious disease transmission [24–26]. The risks asso-ciated with rushed crack smoking are not well described,apart from one study which found a high prevalence ofburns and inhaled metallic crack pipe filter screensamong individuals who reported rushed crack smoking[27]. Therefore, this study sought to investigate theprevalence and correlates of public crack smoking andrushed public crack smoking among participants of twoprospective cohorts of people who use illicit drugs inVancouver, Canada.MethodsData for these analyses were derived from two prospectiveobservational cohorts in Vancouver, Canada: the AIDSCare Cohort to evaluate Exposure to Survival Services(ACCESS) of HIV-seropositive illicit drug users and theVancouver Injection Drug Users Study (VIDUS) ofHIV-seronegative injection drug users. These cohortshave previously been described in detail [28, 29]. In short,since 1996, more than 2000 individuals have been re-cruited into these cohorts through snowball sampling andstreet outreach methods in Vancouver’s DowntownEastside, a post-industrial neighbourhood with an estab-lished drug market and widespread illicit drug use, pov-erty, poor housing conditions, and infectious diseasessuch as HIV and HCV [30].Participants are eligible for VIDUS if they are HIV-seronegative, over 18 years of age, and have injected anillicit drug in the month prior to the baseline interview.Participants are eligible for ACCESS if they are HIV-seropositive, over the age of 18, and have used an illicitdrug other than or in addition to cannabis within themonth prior to the baseline interview. As these two co-horts were originally one single cohort until they were splitinto the two present cohorts in 2005, the two cohortsemploy harmonized data collection and follow-upprocedures to allow for combined analyses of the HIV-seronegative and HIV-seropositive study participants. Spe-cifically, at baseline and semi-annually, participants answeran interviewer-administered questionnaire, which elicitsdata on demographic characteristics, drug-using behav-iours and related exposures; provide blood samples forHIV (for VIDUS participants only) and HCV serologicanalyses; and are referred as necessary to medical care anddrug and alcohol treatment. All participants providewritten informed consent and receive a $30 stipend at theend of each study visit. These studies have received annualethics approval from the University of British Columbiaand Providence Health Care Research Ethics Board.The present analyses were restricted to interviews thatwere conducted between December 1, 2010 to May 31,2014. Participants were eligible for this analysis if theyreported smoking crack at least once in the six-monthperiod prior to their interview, and if they had a historyof ever injecting any drug at the time of interview. Themain outcome measure of interest was smoking crack inVoon et al. BMC Public Health  (2016) 16:476 Page 2 of 9public (always or usually vs. sometimes, occasionally ornever) [31]. The self-reported demographic, behavioural,social and structural explanatory characteristics consid-ered in the analyses were: age (per one-year decrease);gender (female vs. male); HIV serostatus (positive vs. nega-tive); homelessness (yes vs. no); drug dealing (yes vs. no);sex work (yes vs. no); crack smoking (≥ daily vs. < daily);sharing a crack pipe (yes vs. no); binge non-injection druguse (yes vs. no); heroin injection (≥ daily vs. < daily);cocaine injection (≥ daily vs. < daily); crystal methampheta-mine injection (≥ daily vs. < daily); public injection druguse (always or usually vs. sometimes, occasionally ornever); noticing police presence when buying or usingdrugs (yes vs. no); being stopped, searched or detainedwithout arrest by police (yes vs. no); recent incarceration(yes vs. no); enrolment in drug addiction treatment,excluding methadone (yes vs. no); and being a victim ofviolence (yes vs. no). All variables referred to activities orevents in the six months prior to the participant’s inter-view, unless otherwise indicated. As in previous studies,binge non-injection drug use was defined as any period oftime within the previous six months from the time of inter-view during which any drugs were used more frequentlythan usual [32].First, we compared those who did and did not smokecrack in public at baseline using Pearson’s Chi-squaredtest for dichotomous variables and the Wilcoxon ranksum test for continuous variables. Next, since analysesof factors potentially associated with public crack smok-ing included serial measures for each subject, we usedgeneralized estimating equations (GEE) with logit linkfunction and exchangeable working correlation structureto account for correlations between repeated measure-ments. Bivariable GEE analyses were conducted to ob-tain unadjusted odds ratios and p-values for factorsassociated with public crack smoking. Using an a priori-defined statistical protocol based on examination of thequasi-likelihood under the independence model criterion(QIC) value, a preliminary multivariable model was builtusing all variables that were significantly associated with theoutcome at the p < 0.10 in the bivariable analyses. Next,each variable with the highest p-value was removed sequen-tially. The final model included the set of variables associ-ated with the lowest QIC, and was assessed with varianceinflation factors to ensure the absence of multicollinearity.As a secondary analysis, among participants who re-ported any public crack smoking (i.e., always, usually,sometimes, or occasionally), bivariable and multivariableGEE analyses were conducted to determine factors asso-ciated with rushed public crack smoking, using the sameprocedures detailed above. All p-values were two sided.A significant association was defined as p < 0.05. All stat-istical analyses were performed using the SAS softwareversion 9.4 (SAS, Cary, NC).ResultsOf the 1085 participants eligible for the present analysis,400 (36.9 %) were female. The median age at the firststudy visit was 46 (interquartile range: 40—52) years.Participants in this sample contributed to a total of 5126observations during the study period. Table 1 shows thebaseline sample characteristics. At the first study visit,244 (22.5 %) participants reported “always” or “usually”smoking crack in public in the previous six months.During the 42-month study period, 379 (34.9 %) partici-pants reported “always” or “usually” smoking crack inpublic at least once.Table 2 presents the results of the bivariable and multi-variable GEE analyses. In multivariable GEE analyses, fac-tors that remained positively and independently associatedwith public crack smoking included: public injection druguse (adjusted odds ratio [AOR]: 5.42, 95 % confidenceinterval [CI]: 3.76-7.82), homelessness (AOR: 3.48, 95 %CI: 2.77-4.36), at least daily crack use (AOR: 2.69, 95 % CI:2.19-3.31), crack pipe sharing (AOR: 1.98, 95 % CI:1.60-2.46), drug dealing (AOR: 1.59, 95 % CI: 1.30-1.94),recent incarceration (AOR: 1.47, 95 % CI: 1.09-1.98), no-ticing police presence (AOR: 1.30, 95 % CI: 1.06-1.60), andyounger age (AOR: 1.03, 95 % CI: 1.01-1.04).Of the 751 participants who smoked crack in public atleast once, rushed public crack smoking was reported by216 (28.8 %) participants at least once during the studyperiod. Table 3 shows the factors positively and inde-pendently associated with rushed public crack smokingin multivariable GEE analyses, which included: home-lessness (AOR: 2.61, 95 % CI: 1.96-3.49), at least dailycrack use (AOR: 1.48, 95 % CI: 1.11-1.98), crack pipesharing (AOR: 1.44, 95 % CI: 1.10-1.89), drug dealing(AOR: 1.39, 95 % CI: 1.04-1.86), and younger age (AOR:1.02, 95 % CI: 1.01-1.04).DiscussionIn this study, more than one-third of participants whohad smoked crack reported “always or usually” smokingcrack in public at some point during the study period.Of the participants who had smoked crack in public atleast once, 28.8 % reported rushed public crack smoking.This study found that individuals who were homelesshad elevated odds of public crack use and rushed publiccrack use compared to individuals who were not home-less, which is consistent with other literature that hasfound that homelessness is one of the strongest predic-tors of using injection drugs in public [22, 33–35].Among individuals who use crack in particular, rates ofhomelessness have been found to be disproportionatelyhigher than individuals who use other illicit drugs [2].Therefore, one way to reduce risky public crack use mayinvolve addressing barriers to securing stable housingamong this population, such as increasing accessibilityVoon et al. BMC Public Health  (2016) 16:476 Page 3 of 9Table 1 Baseline characteristics of VIDUS and ACCESS participants who smoked crack in Vancouver, Canada, stratified by publiccrack smoking (n = 1085)Characteristic Smoked crack in publica244 (22.5 %)n (%)Did not smoke crack in publicb841 (77.5 %)n (%)Odds ratio (95 % CI) p - valueAgeMedian years 42.1 47.2 1.05 (1.04, 1.08) <0.001(IQR) (36.1 – 47.0) (40.7 – 52.5)GenderFemale 93 (38.1) 307 (36.5) 1.07 (0.80, 1.44) 0.646Male 151 (61.9) 534 (63.5)HIV serostatusPositive 90 (36.9) 406 (48.3) 0.63 (0.47, 0.84) 0.002Negative 154 (63.1) 435 (51.7)Homelessnessc,dYes 115 (47.1) 109 (13.0) 6.02 (4.36, 8.31) <0.001No 128 (52.5) 730 (86.8)Drug DealingcYes 106 (43.4) 156 (18.5) 3.37 (2.48, 4.59) <0.001No 138 (56.6) 685 (81.5)Sex workc, aYes 40 (16.4) 95 (11.3) 1.56 (1.05, 2.33) 0.029No 201 (82.4) 745 (88.6)Crack smokingc,d≥ Daily 136 (55.7) 254 (30.2) 2.90 (2.16, 3.89) <0.001< Daily 108 (44.3) 585 (69.6)Shared crack pipecYes 143 (58.6) 384 (45.7) 1.68 (1.26, 2.25) <0.001No 101 (41.4) 457 (54.3)Binge non-injection drug usecYes 99 (40.6) 341 (40.5) 1.01 (0.75, 1.34) 0.994No 145 (59.4) 500 (59.5)Heroin injectionc≥ Daily 78 (32.0) 113 (13.4) 3.03 (2.17, 4.23) <0.001< Daily 166 (68.0) 728 (86.6)Cocaine injectionc,d≥ Daily 28 (11.5) 43 (5.1) 2.40 (1.46, 3.95) <0.001< Daily 216 (88.5) 796 (94.6)Crystal meth injectionc≥ Daily 10 (4.1) 27 (3.2) 1.29 (0.61, 2.70) 0.501< Daily 234 (95.9) 814 (96.8)Public injection drug usec,dAlways or usually 59 (24.2) 19 (2.3) 13.80 (8.04, 23.72) <0.001Sometimes, occasionally or never 184 (75.4) 818 (97.3)Voon et al. BMC Public Health  (2016) 16:476 Page 4 of 9to supportive housing and housing support staff whomay assist with issues such as social assistance andtenancy rights [22].In this study, individuals who smoked crack in publichad a five-fold increased odds of also having injecteddrugs in public, which is concerning given the added riskof infection and disease transmission associated withpublic injection drug use [21–23]. Daily crack use andcrack pipe sharing were also significantly associated withpublic crack use and rushed public crack use. Thesefindings suggest that individuals who smoke crack inpublic may at increased risk of transmitting HIV, HCVand other infectious pathogens [7–15]. The finding thatrushed public crack use was significantly associated withcrack pipe sharing is especially concerning, given thatrushed drug use is often characterized by inattention tohygiene and harm reduction practices, which may fur-ther exacerbate the risk of infectious disease transmis-sion [24–26]. Therefore, greater efforts are needed toreduce barriers to distributing sterile crack pipes to re-duce risky pipe sharing, especially given literature sug-gesting that crack pipe sharing is significantly associatedwith difficulty obtaining new pipes [31, 36].Individuals who used crack in public in the presentstudy demonstrated higher odds of recent incarcerationand noticing police presence. These findings echo otherresearch that has found that individuals who use drugsin public are often involved in the criminal justice sys-tem [23, 33, 34, 37] and are often fearful of, hassled, orshamed by police, which may perpetuate drug use inriskier environments perceived to be less exposed to po-lice (e.g., alleys, dumpsters, hidden doorways) [26, 35].However, such hidden environments often pose high riskfor fatal overdose due to individuals being out of sightfrom passersby, injury or infection due to hazardouslitter that is frequently found in such areas (e.g., usedneedles or crack pipes), or lack of access to sterile sup-plies in such settings [21, 26].Individuals who reported public crack use and rushedpublic crack use were also more likely to have recentlyengaged in drug dealing. A limited body of literature hasfound that public crack use is associated with drug deal-ing [37], and that crack users are more likely than non-crack users to report illegal activities such as drugdealing as a method of income generation [15]. One po-tential explanation is that drug dealing and public crackuse both occur at street level, where individuals mayspend a large portion of their time [18]. Therefore,street-level harm reduction interventions such as utiliz-ing street outreach programs to distribute sterile druguse equipment and provide safer drug use educationmay be beneficial for this population [38, 39]. Addition-ally, improving access to low-threshold employment op-portunities for this population may reduce the need forindividuals to rely on street-level income-generatingactivities, and in turn potentially reduce drug use andrelated harms [40].Collectively, these findings suggest the potential forevidence-based public health interventions to reduce theharms associated with public crack use and rushedTable 1 Baseline characteristics of VIDUS and ACCESS participants who smoked crack in Vancouver, Canada, stratified by publiccrack smoking (n = 1085) (Continued)Noticed police presencec,dYes 175 (71.7) 536 (63.7) 1.47 (1.07, 2.02) 0.016No 67 (27.5) 302 (35.9)Stopped, searched or detained without arrest by policec,dYes 57 (23.4) 90 (10.7) 2.62 (1.81, 3.80) <0.001No 181 (74.2) 750 (89.2)Incarcerationc, aYes 43 (17.6) 55 (6.5) 3.13 (2.04, 4.81) <0.001No 196 (80.3) 785 (93.3)Drug addiction treatment (excluding methadone)c,dYes 148 (60.7) 525 (62.4) 0.96 (0.71, 1.28) 0.766No 92 (37.7) 312 (37.1)Victim of violencec,dYes 39 (16.0) 128 (15.2) 1.08 (0.73, 1.59) 0.710No 200 (82.0) 707 (84.1)aDefined as “always” or “usually” smoking crack in public in the previous six monthsbDefined as “sometimes,” “occasionally” or “never” smoking crack in public in the previous six monthscDenotes activities/events in the previous six monthsdCounts may not add up to column totals due to missing responsesVoon et al. BMC Public Health  (2016) 16:476 Page 5 of 9public crack use. While the evidence in support ofsupervised injection facilities is now well-established[41–45], the implementation of supervised inhalationrooms has been slow to follow suit, despite the over-whelming benefit that such facilities may offer in termsof providing a safe, non-rushed environment; sterileequipment to prevent disease transmission; direct accessto health and social services for this hard-to-engagepopulation prone to fatal overdose, infection, and othercomplex health concerns; immediate support for addic-tion treatment and counselling; reducing public drug useand related disorder; and affording considerable costTable 2 Bivariable and multivariable GEE analyses of factors associated with public crack smoking in the previous six months amongVIDUS and ACCESS participants who smoked crack in Vancouver, Canada (n = 1085)Unadjusted AdjustedCharacteristic Odds ratio (95 % CI) p-value Odds ratio (95 % CI) p-valueAge(per one-year decrease) 1.06 (1.05 – 1.08) <0.001 1.03 (1.01 – 1.04) <0.001Gender(female vs. male) 1.09 (0.86 – 1.39) 0.465HIV serostatus(positive vs. negative) 0.71 (0.56 – 0.91) 0.006Homelessnessa(yes vs. no) 4.55 (3.71 – 5.59) <0.001 3.48 (2.77 – 4.36) <0.001Drug dealinga(yes vs. no) 2.76 (2.30 – 3.32) <0.001 1.59 (1.30 – 1.94) <0.001Sex worka(yes vs. no) 1.94 (1.48 – 2.54) <0.001Crack smokinga(≥ daily vs. < daily) 3.11 (2.59 – 3.74) <0.001 2.69 (2.19 – 3.31) <0.001Shared crack pipea(yes vs. no) 2.78 (2.31 – 3.34) <0.001 1.98 (1.60 – 2.46) <0.001Binge non-injection drug usea(yes vs. no) 1.44 (1.24 – 1.67) <0.001Heroin injectiona(≥ daily vs. < daily) 2.21 (1.72 – 2.84) <0.001Cocaine injectiona(≥ daily vs. < daily) 1.48 (1.09 – 1.99) 0.011Crystal meth injectiona(≥ daily vs. < daily) 0.89 (0.57 – 1.40) 0.626Public injection drug usea(Always or usually vs. sometimes, occasionally or never) 7.46 (5.42 – 10.28) <0.001 5.42 (3.76 – 7.82) <0.001Noticed police presencea(yes vs. no) 1.67 (1.42 – 1.97) <0.001 1.30 (1.06 – 1.60) 0.013Stopped, searched or detained without arrest by policea(yes vs. no) 1.98 (1.61 – 2.44) <0.001Incarcerationa(yes vs. no) 2.36 (1.79 – 3.11) <0.001 1.47 (1.09 – 1.98) 0.011Drug addiction treatment (excluding methadone)a(yes vs. no) 0.95 (0.78 – 1.16) 0.622Victim of violencea(yes vs. no) 1.52 (1.22 – 1.88) <0.001aDenotes activities/events in the previous six monthsVoon et al. BMC Public Health  (2016) 16:476 Page 6 of 9savings for health care systems [15, 46–49]. Notably, theimplementation of supervised inhalation rooms need notbe separate from supervised injection facilities; in fact,the delivery of both supervised injection and inhalation(or other non-injection drug use) in a single ‘safe druguse facility’ may be a more feasible and accessible ap-proach for this population. Although individuals whouse crack have previously reported high rates of willing-ness to use supervised inhalation rooms [27, 37, 50],policy barriers continue to impede the implementationof these potentially life-saving facilities [51].In addition to the social and structural interventionsdescribed above, more immediate public health interven-tions to reduce the harms associated with public crackuse may include distributing sterile crack smokingequipment and installing safe disposal containers forused crack equipment in public places [21, 35, 52, 53].Notably, these interventions hold benefit for users ofother non-injection drugs (e.g., methamphetamine,heroin), and may even play a crucial role in supportingthe transition from injection drug use to less risky formsof non-injection drug use [46, 52, 54]. Furthermore,more research is needed on effective treatments forstimulant dependence, as currently no single approachhas yet shown consistent evidence for effectively redu-cing or sustaining abstinence for stimulant use [55–59].This study has several limitations. First, our study re-lied on self-reported data that is susceptible to sociallydesirable reporting and recall bias. Second, because thestudy sample was not randomly selected, these resultsmay not be generalizable to other populations. Relatedto this, as there is a lack of research on crack cocaineuse in general population samples—including estimatesof co-occurring crack smoking and injection drug useTable 3 Bivariable and multivariable GEE analyses of factors associated with rushed public crack smoking in the previous six monthsamong VIDUS and ACCESS participants in Vancouver, Canada who smoked crack in public at least once (n = 751)Unadjusted AdjustedCharacteristic Odds ratio (95 % CI) p-value Odds ratio (95 % CI) p-valueAge(per one-year decrease) 1.04 (1.02 – 1.06) <0.001 1.02 (1.01 – 1.04) 0.019Gender(female vs. male) 1.35 (1.01 – 1.80) 0.045 1.23 (0.90 – 1.69) 0.185Homelessnessa(yes vs. no) 2.86 (2.18 – 3.76) <0.001 2.61 (1.96 – 3.49) <0.001Drug dealinga(yes vs. no) 1.86 (1.41 – 2.44) <0.001 1.39 (1.04 – 1.86) 0.026Sex worka(yes vs. no) 1.25 (0.86 – 1.81) 0.241Crack smokinga(≥ daily vs. < daily) 1.71 (1.30 – 2.24) <0.001 1.48 (1.11 – 1.98) 0.007Shared crack pipea(yes vs. no) 1.65 (1.28 – 2.14) <0.001 1.44 (1.10 – 1.89) 0.008Binge non-injection drug usea(yes vs. no) 1.28 (1.00 – 1.64) 0.051Noticed police presencea(yes vs. no) 1.19 (0.88 – 1.60) 0.250Stopped, searched or detained without arrest by policea(yes vs. no) 1.68 (1.22 – 2.31) 0.001Incarcerationa(yes vs. no) 1.90 (1.30 – 2.78) <0.001 1.43 (0.95 – 2.15) 0.084Drug addiction treatment (excluding methadone)a(yes vs. no) 0.97 (0.73 – 1.28) 0.828Victim of violencea(yes vs. no) 1.36 (0.96 – 1.92) 0.088aDenotes activities/events in the previous six monthsVoon et al. BMC Public Health  (2016) 16:476 Page 7 of 9and estimates of public crack smoking—it is difficult tocompare these findings to other populations. Therefore,more research on crack smoking in general populationsamples is needed. Finally, as in all observational studiesof this kind, the associations between the explanatoryvariables and the outcomes assessed may have beenunder the influence of unmeasured confounding, al-though we sought to address this bias with multivariableadjustment involving key potential correlates of publiccrack smoking.ConclusionsIn summary, a high prevalence of public crack smokingand rushed public crack smoking was observed in thisstudy. These behaviours were associated with an array offactors highlighting the vulnerability of this population,including homelessness, younger age, public injectiondrug use, daily crack use, crack pipe sharing, exposureto law enforcement, and involvement in drug dealing.These findings point to the need for implementing andevaluating evidence-based social, structural, and publichealth interventions, such as supervised inhalationfacilities, to reduce the risks and harms associated withsmoking crack in public.AbbreviationsACCESS, AIDS Care Cohort to Evaluate Access to Survival Services; AIDS, acquiredimmune deficiency syndrome; AOR, adjusted odds ratio; CI, confidence interval;GEE, generalized estimating equations; HCV, hepatitis C virus; HIV, humanimmunodeficiency virus; QIC, independence model criterion; VIDUS, VancouverInjection Drug Users StudyAcknowledgementsThe authors thank the ACCESS and VIDUS study participants for theircontribution to the research, as well as current and past researchers andstaff. We would specifically like to thank Sabina Dobrer, Tricia Collingham,Carmen Rock, Deborah Graham, Peter Vann, Jennifer Matthews, and SteveKain for their assistance with this research.FundingThis study was supported by the U.S. National Institutes of Health(U01DA038886 and R01DA021525). This research was undertaken, in part,thanks to funding from the Canada Research Chairs program through aTier 1 Canada Research Chair in Inner City Medicine, which supportsDr. Evan Wood. Dr. Kanna Hayashi is supported by the Canadian Institutes ofHealth Research New Investigator Award (MSH-141971). Dr. M-J Milloy issupported in part by the U.S. NIH (R01DA021525). Dr. Lianping Ti is supportedby the Canadian Institutes of Health Research Fellowship Award. Pauline Voonis supported by the Vanier Canada Graduate Scholarships and the CanadianNurses Foundation. The funding bodies had no role in the study design, datacollection, analysis, interpretation, or manuscript writing.Availability of data and materialsThe data used for this study is not publicly available. For further informationon the data and materials used in this study, please contact thecorresponding author.Authors’ contributionsEW, TK, MJM and KH directed the cohort studies. PV, LT, TK and KH designed thepresent study. HD conducted the statistical analyses. PV developed the first draftand incorporated suggestions from all co-authors. All authors made significantcontributions to the conception of the analyses, interpretation of the data, anddrafting of the manuscript. All authors read and approved the final manuscript.Competing interestsThe authors declare that they have no competing interests.Consent for publicationNot applicable.Ethics approval and consent to participateAll participants provided written informed consent for study participation.The cohort studies received annual ethics approval from the University ofBritish Columbia and Providence Health Care Research Ethics Board. ThePrincipal Investigators of the cohorts (Drs. Kerr and Milloy) grantedpermission to use the data for the present study, which was part of thelarger cohort study activities that receive annual ethics approval by theaforementioned Research Ethics Boards.Author details1Urban Health Research Initiative, British Columbia Centre for Excellence inHIV/AIDS, St. Paul’s Hospital, 608-1080 Burrard Street, Vancouver, BC V6Z 1Y6,Canada. 2School of Population and Public Health, Faculty of Medicine,University of British Columbia, 2206 East Mall, Vancouver, BC V6Z 1Z3,Canada. 3Department of Medicine, University of British Columbia, St. Paul’sHospital, 608-1081 Burrard Street, Vancouver, BC V6Z 1Y6, Canada.Received: 8 January 2016 Accepted: 19 May 2016References1. UHRI. Drug situation in Vancouver (Second Edition). In: Urban HealthResearch Initiative, British Columbia Centre for Excellence in HIV/AIDS.2nd ed. 2013.2. Fischer B, Coghlan M. Crack use in North American cities: the neglected‘epidemic’. Addiction. 2007;102(9):1340–1.3. 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