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Incidence and risk factors for non-fatal overdose among a cohort of recently incarcerated illicit drug… Kinner, Stuart A.; Milloy, M-J; Wood, Evan; Qi, Jiezhi; Zhang, Ruth; Kerr, Thomas Feb 7, 2012

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Incidence and risk factors for non-fatal overdose among acohort of recently incarcerated illicit drug usersStuart A. Kinnera,b,c,*, M-J. Milloyd,e, Evan Woodd,f, Jiezhi Qid, Ruth Zhangd, and ThomasKerrd,faCentre for Population Health, Burnet Institute 85 Commercial Road Melbourne, VIC, 3004AustraliabSchool of Population Health, University of Queensland, Brisbane, AustraliacSchool of Public Health and Preventive Medicine, Monash University, Melbourne, AustraliadBritish Columbia Centre for Excellence in HIV/AIDS, St Paul’s Hospital 608-1081 Burrard StreetVancouver, BC, Canada V6Z 1Y6eSchool of Population and Public Health, University of British Columbia, Vancouver, CanadafDepartment of Medicine, University of British Columbia, Vancouver, CanadaAbstractBackground—Release from prison is associated with a markedly increased risk of both fatal andnon-fatal drug overdose, yet the risk factors for overdose in recently released prisoners are poorlyunderstood. The aim of this study was to identify risk and protective factors for non-fatal overdose(NFOD) among a cohort of illicit drug users in Vancouver, Canada, according to recentincarceration.Methods—Prospective cohort of 2515 community-recruited illicit drug users in Vancouver,Canada, followed from 1996 to 2010. We examined factors associated with NFOD in the past sixmonths separately among those who did and did not also report incarceration in the last sixmonths.Results—One third of participants (n=829, 33.0%) reported at least one recent NFOD. Amongthose recently incarcerated, risk factors independently and positively associated with NFODincluded daily use of heroin, benzodiazepines, cocaine or methamphetamine, binge drug use,public injecting and previous NFOD. Older age, methadone maintenance treatment and HIVseropositivity were protective against NFOD. A similar set of risk factors was identified amongthose who had not been incarcerated recently.Conclusions—Among this cohort, and irrespective of recent incarceration, NFOD wasassociated with a range of modifiable risk factors including more frequent and riskier patterns ofdrug use. Not all ex-prisoners are at equal risk of overdose and there remains an urgent need to© 2012 Elsevier Ltd. All rights reserved.*Corresponding author at: Burnet Institute 85 Commercial Rd, Melbourne VIC, 3004 Australia. Tel.: +61 3 8506 2368; fax: +61 39282 2138. kinner@burnet.edu.au (S.A. Kinner).ContributorsAuthors Kerr and Wood designed the study. Authors Qi and Zhang undertook the statistical analyses. Author Kinner wrote the firstdraft of the manuscript. All authors contributed to and have approved the final manuscript.Conflict of interestNo conflict declared.NIH Public AccessAuthor ManuscriptAddict Behav. Author manuscript; available in PMC 2013 June 01.Published in final edited form as:Addict Behav. 2012 June ; 37(6): 691–696. doi:10.1016/j.addbeh.2012.01.019.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptdevelop and implement evidence-based preventive interventions, targeting those with modifiablerisk factors in this high risk group.KeywordsOverdose; Ex-prisoners; Drug users1. IntroductionRelease from prison is associated with a markedly increased risk of fatal drug overdose,particularly in the weeks immediately following discharge. Evidence from record linkagestudies suggests that the risk of drug-related death is orders of magnitude higher among ex-prisoners than among their community peers (Binswanger et al., 2007; Farrell & Marsden,2008; Kariminia et al., 2007; Rosen, Schoenbach, & Wohl, 2008; Stewart, Henderson,Hobbs, Ridout, & Knuiman, 2004), and between 3 and 8 times higher in the first two weeksthan the subsequent ten weeks (Merrall et al., 2010). Although it is often assumed that thekey driver of overdose risk for ex-prisoners is reduced drug tolerance (Merrall et al., 2010;Seaman, Brettle, & Gore, 1998; Strang et al., 2003), empirical support for this view remainsweak (Kinner, 2010).Reducing the incidence of overdose among recently released prisoners requires anunderstanding of who is most at risk and why, so that interventions to prevent or effectivelyrespond to overdose events can be appropriately targeted and tailored (Darke, 2008).Unfortunately, although record linkage studies have identified that ex-prisoners are atincreased risk of overdose death, limitations of routinely collected data mean that few riskfactors for fatal overdose in this population have been identified (Kinner, 2010). Existingevidence suggests that those most at risk have served multiple prison sentences, lack post-release support from a spouse or partner, and have a history of illicit opiate use (Graham,2003; Hobbs et al., 2006a; Rosen et al., 2008; Seaman et al., 1998; Singleton, Pendry,Taylor, Farrell, & Marsden, 2003). Findings regarding age and ethnic minority status havebeen mixed, with some studies finding that older and ethnic minority ex-prisoners are atgreater risk (Hobbs et al., 2006b; Stewart et al., 2004; Tobin, Hua, Costenbader, & Latkin,2007), while others have found the converse (Farrell & Marsden, 2005; Graham, 2003).Perhaps reflecting reduced drug tolerance, one study has identified abstinence from drug usein prison as a risk factor for drug-related death post-release (Singleton et al., 2003), whileengagement in prison-based methadone maintenance treatment (MMT) appears to beprotective (Dolan et al., 2005; Kinlock, Gordon, Schwartz, Fitzgerald, & O’Grady, 2009).Nonfatal overdose (NFOD) is estimated to be between 20 and 30 times more common thanfatal overdose (Darke, Mattick, & Degenhardt, 2003), and is associated with significantmorbidity (Warner-Smith, Darke, & Day, 2002). Relatively few studies have explored riskfactors for NFOD (Strang, 2002) and although the causes of fatal and non-fatal overdose arelikely to be similar (Warner-Smith, Darke, Lynskey, & Hall, 2001), very few studies haveexamined NFOD among ex-prisoners. Most studies of NFOD have followed cohorts ofinjecting drug users (IDU), and a history of recent incarceration consistently emerges as akey risk factor (Kerr, Fairbairn, et al., 2007; Seal et al., 2001; Yin et al., 2007). Otheridentified risk factors include homelessness, a history of multiple arrests and/orimprisonments, longer prison sentences, detoxification in the past year, riskier patterns ofinjecting such as public injecting and binge drug use, and regular or concurrent use ofmultiple drugs including heroin, alcohol, benzodiazepines and cocaine (Coffin et al., 2007;Kerr, Fairbairn, et al., 2007; Seal et al., 2001; Sergeev, Karpets, Sarang, & Tikhonov, 2003;Yin et al., 2007). Consistent with the findings from record linkage studies, MMT appears tobe protective (Kerr, Fairbairn, et al., 2007), as does older age (Coffin et al., 2007; Kerr,Kinner et al. Page 2Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptFairbairn, et al., 2007; Seal et al., 2001). Although empirical evidence remains limited, it hasbeen argued that systemic disease, particularly hepatic disease associated with hepatitis Cinfection, may increase the risk of overdose (Warner-Smith et al., 2001).Given the high incidence of overdose among those recently released from prison, andlimited knowledge of the risk factors for NFOD among this population, the aims of thepresent study were to (a) document the incidence of NFOD among a large cohort of illicitdrug users in Vancouver, Canada, separately for those who had and had not experiencedincarceration recently, and (b) in a multivariate model, identify risk and protective factorsfor NFOD among this cohort, separately for those who had and had not experiencedincarceration recently.2. MethodsThe Vancouver Injection Drug Users Study (VIDUS) and AIDS Care Cohort to EvaluateAccess to Survival Services (ACCESS) are open prospective cohorts of illicit drug-usingindividuals who have been recruited through self-referral and street outreach fromVancouver’s Downtown Eastside since May 1996. Those recruited into the VIDUS cohortare HIV-negative and must have injected an illicit drug at least once in the past six months.Those recruited into the ACCESS cohort are HIV-positive and must have used an illicit drugother than or in addition to cannabis in the last 30 days. Members of the VIDUS cohort whoseroconvert during follow-up are automatically transferred into the ACCESS cohort.At baseline and every six months, participants in both cohorts provide venous blood samplesfor HIV and hepatitis C (HCV) testing and complete an interviewer-administeredquestionnaire covering demographic characteristics, information about drug use and relatedharms, HIV risk behavior, contact with the criminal justice system and enrolment in drugtreatment. All participants provide informed, written consent and receive a CA$20 stipend ateach study visit. The study has been approved by the University of British Columbia’sResearch Ethics Board.The present analyses included all participants who were enrolled into either VIDUS orACCESS between May 1996 and May 2010 (N=2515). The primary endpoint was self-reported NFOD during the previous six months. Because the focus of the study was NFODin the community, interviews conducted in prison settings (n=424) were excluded.Information on the primary drug involved in overdose was collected from 2001 onwards.Explanatory variables were selected from those identified in the literature and includeddemographic characteristics, patterns of drug use, methadone maintenance treatment(MMT), HIV and HCV serostatus. Demographic characteristics included age, gender,Aboriginal ancestry, marital status, employment status, living alone and currenthomelessness. Drug use variables included daily use of heroin, cocaine, speedballs (cocaineand heroin in combination), methamphetamine, morphine, benzodiazepines and >4 alcoholicdrinks; binge drug use and public injecting. For those who reported recent incarceration,additional explanatory variables included drug injection in prison and, as a proxy forsentence length, incarceration setting (local/provincial/federal). In Canada, incarceration inlocal jails typically lasts for days or weeks, sentences in provincial prisons are up to twoyears less a day, and all sentences of two years or more are served in federal penitentiaries.All time-variant variables referred to the last six months unless otherwise specified.In order to explore whether the risk factors for NFOD differed as a function of recentincarceration, the sample was divided into those who did and did not report incarceration inthe last six months. Within each sub-group, we first graphed the annual crude incidence rateof NFOD per 1000 person years, by dividing the number of NFODs reported in eachKinner et al. Page 3Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptcalendar year (1996–2010) by the total person years of observation in that year (defined asthe number of observations divided by two), divided by 1000. Next we examined univariateassociations between potential explanatory variables and NFOD using Pearson’s Chi-Squaretest and the Wilcoxon Rank Sum test; variables significant at p<0.10 were included insubsequent multivariate analyses. Because the analysis included repeated measures ofpotential explanatory variables for each participant, we used generalized estimatingequations (GEE) for binary outcomes with logit link for the analysis of correlated data, toidentify factors independently associated with NFOD (Liang & Zeger, 1986). Multivariatemodel building proceeded according to the protocol outlined by Pan (2001).3. ResultsBetween May 1996 and May 2010 2515 participants were recruited into the study,contributing a total of 21,798 eligible observations across a median of six follow-up visits(IQR=2–14). Among this cohort 829 (33.0%) participants reported a total of 1587 NFODs.Among those recently incarcerated who experienced NFOD, 215 (39%) identified theprimary drug involved: 81.4% identified a CNS depressant (typically heroin), while 18.1%identified only a stimulant (typically cocaine). Among those who experienced NFOD andhad not been incarcerated recently 637 (62%) identified the primary drug involved: 77.2%identified a CNS depressant and 22.3% identified only a stimulant.Table 1 provides descriptive statistics for those who did and did not report recentincarceration at baseline. Factors positively associated with recent incarceration includedyounger age; male gender; homelessness; unemployment; prior incarceration; daily use ofheroin, cocaine, speedballs, morphine and benzodiazepines; recent binge drug use andpublic injecting; and history of overdose. Factors negatively associated with recentincarceration at baseline included HIV infection, living alone and MMT.Fig. 1 shows the crude incidence rate of NFOD per 1000 person years of observation, amongthose who did and did not report recent incarceration, by year 1996–2010. Over this 15 yearperiod those reporting recent incarceration experienced a total of 554 NFODs giving a crudeincidence rate of 262.7 per 1000 person years of observation, compared with 1035 NFODsand a crude incidence rate of 117.7 per 1000 person years among those who did not reportrecent incarceration. Those recently incarcerated were significantly more likely to reportrecent NFOD (OR=2.13, 95%CI 1.89–2.40, p<0.001).Factors associated with NFOD among those who did and did not report recent incarcerationare shown in Table 2. Among those who reported recent incarceration, factors significantlyassociated with NFOD in univariate GEE analyses included younger age; homelessness;daily use of heroin, cocaine, speedballs, methamphetamine and benzodiazepines; binge druguse and public injecting; drug injection while incarcerated; and previous NFOD. MMT andHIV infection were protective. Among those who did not report recent incarceration, thesame factors were significant, except that daily alcohol use emerged as an additional riskfactor, and both previous (not recent) incarceration and HCV exposure were significantlyprotective.Table 2 also shows factors independently associated with NFOD in multivariate GEEanalysis, separately for those who did and did not report recent incarceration. Among thosereporting recent incarceration, NFOD was independently associated with daily use of heroin(AOR=1.29, 95%CI 1.05–1.59), cocaine (AOR=1.49, 95%CI 1.22–1.83), methamphetamine(AOR=1.98, 95%CI 1.21–3.22) and benzodiazepines (AOR=1.90, 95%CI 1.29–2.80); bingedrug use (AOR=1.67, 95%CI 1.38–2.03) and public injecting (AOR=1.34, 95%CI 1.10–1.65); and previous NFOD (AOR=3.87, 95%CI 2.97–5.03). Being older (AOR=0.98 peryear, 95%CI 0.97–0.99), HIV positive (AOR=0.77, 95%CI 0.61–0.99) and receiving MMTKinner et al. Page 4Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscript(AOR=0.64, 95%CI 0.48–0.85) were protective. Among those who did not report recentincarceration a similar pattern emerged, except that homelessness (AOR=1.31, 95%CI 1.04–1.64) and daily alcohol use (AOR=1.28, 95%CI 1.03–1.60) emerged as additional riskfactors, previous (not recent) incarceration was protective (AOR=0.80, 95%CI 0.66–0.96),and being HIV positive was not significantly protective (p>0.05).Given the unexpected protective effect of HIV for those recently incarcerated, we computedall two-way interactions between HIV and other factors significant in the multivariatemodel. The interaction between HIV and age was significant (p=0.02), and in a subsequenttest of interaction effects (see Table 3) HIV emerged as protective for those ≤38 years of age(AOR=0.65, 95%CI 0.47–0.88), whereas among those who were HIV negative, being aged>38 years was protective (AOR=0.74, 95%CI 0.58–0.95).4. DiscussionIn the present study we found that among a large cohort of illicit drug users, the incidence ofNFOD was significantly higher among those who had experienced recent incarceration.However, the risk factors for NFOD were very similar for those who had and had notexperienced recent incarceration, indicating that preventive interventions designed forcommunity-based illicit drug users may also be appropriate for those recently released fromprison. Given that most of the risk factors identified pertain to behaviors and circumstancesin the community, preventive interventions delivered prior to release should be coupled withcommunity-based interventions after release (Freudenberg, Daniels, Crum, Perkins, &Richie, 2005; Kinner, 2010; WHO, 2010).Although many IDU continue to use and inject drugs in prison (Calzavara et al., 2003;Dolan et al., 2010; Jürgens, Ball, & Verster, 2009), much of the debate regarding preventionof overdose in ex-prisoners has focused on reduced drug tolerance (Merrall et al., 2010;Seaman et al., 1998; Strang et al., 2003). Although we were unable to directly measure drugtolerance, our finding that drug injection in prison was a risk factor for NFOD seemsinconsistent with the view that reduced drug tolerance is the overriding risk factor. Althoughit is highly likely that drug tolerance is one important factor, this study has identified a rangeof other, modifiable risk factors for NFOD, which are very similar to those identified forillicit drug users who have not been incarcerated recently.The finding that more frequent, riskier patterns of drug injection was a risk factor for NFODis not new (Kerr, Fairbairn, et al., 2007), although this study confirms that the same is truefor illicit drug users who have been incarcerated recently. Regardless of recent incarceration,risk of NFOD was increased for those reporting public injection or binge drug use. Previouswork has shown that accessing a supervised injection facility (SIF) is associated with areduction in public drug use and other risky injecting practices (Stoltz et al., 2007), and thatSIFs can reduce overdose morbidity (Kerr, Small, Moore, & Wood, 2007; Kerr, Tyndall,Lai, Montaner, & Wood, 2006) and mortality (Milloy, Kerr, Tyndall, Montaner, & Wood,2008). Given the elevated incidence of NFOD among those recently incarcerated in thisstudy, there is a clear case for routinely linking incarcerated IDU with a SIF, whereavailable, both via in-reach before release and as part of a broader case managementapproach after release from custody.Also consistent with previous research (Kerr, Fairbairn, et al., 2007; Ochoa et al., 2005), andregardless of recent incarceration history, risk of NFOD in this study was elevated for thosereporting daily use of heroin, benzodiazepines, cocaine or methamphetamines. We wereunable to determine whether these drugs were used sequentially or in combination, howeverour findings demonstrate that a range of drugs – both depressants and stimulants – areimplicated in overdose among those recently incarcerated. In addition to cautioningKinner et al. Page 5Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptprisoners that their opiate tolerance may be reduced post-release, preventive interventionsshould incorporate messages about the risk of overdose associated with stimulant drugs suchas cocaine and methamphetamine.Previous studies have identified a link between in-prison MMT and reduced overdosemortality post-release (Dolan et al., 2005; Kinlock et al., 2009), although it remains unclearwhether in-prison MMT confers a direct protective effect through increased opiate toleranceat the point of release, or an indirect protective effect by increasing the likelihood ofaccessing MMT in the community. In this study, regardless of recent incarceration, currentMMT was associated with reduced risk of NFOD, highlighting both the benefits of MMT asa harm reduction measure and the particular importance of continuity in treatment provisionfor IDU returning from custody to the community (Dolan et al., 2005; Kinner, 2006; Larney,Toson, Burns, & Dolan, 2012; Møller et al., 2010; Palepu et al., 2004; Wang et al., 2008).Irrespective of recent incarceration, risk of NFOD also decreased with increasing age.Although inconsistent with the view that age-related systemic dysfunction should increasethe risk of overdose (Warner-Smith et al., 2001), these findings are consistent with those ofother studies (Coffin et al., 2007; Kerr, Fairbairn, et al., 2007) and may indicate that olderillicit drug users are ‘aging out’ of the risky behaviors that increase risk of NFOD. Thisinterpretation is consistent with evidence that impulse control is a risk factor for NFOD(Hakansson, Schlyter, & Berglund, 2008) and that impulsivity declines with age (Steinberget al., 2008).Among those recently incarcerated, risk of NFOD was lower for those who were HIVpositive, although this was only true for younger ex-prisoners. One interpretation of thisfinding is that among younger ex-prisoners, HIV diagnosis was associated with increasedaccess to care and treatment, and a corresponding reduction in overdose risk behaviors. Bycontrast, given the high prevalence of HIV among the cohort, among older users remaininguninfected with HIV may have been a marker for lower levels of overdose risk behavior.Although potentially important, it remains unclear why this marginally significant findingwas observed and future research could further explore these dynamics.In this study the most powerful predictor of NFOD was past experience of overdose. Amongthose who had been incarcerated recently, the risk of NFOD was almost four times greaterfor those who had also overdosed in the past. This finding adds to a growing literature(Coffin et al., 2007; Darke et al., 2007; Stoové, Dietze, & Jolley, 2009) suggesting thatprevious overdose experience does not increase the perception of risk for subsequentoverdose (Darke & Ross, 1997), but rather increases risk. In the context of limited resourcesfor prisoner and ex-prisoner health initiatives (Belenko & Peugh, 2005; Levy, 2005),identification of those most at risk of overdose may allow for more effective allocation oflimited resources for prevention. In addition to education and case management, this mayinclude provision of naloxone to those considered at high risk (Ochoa et al., 2005;Wakeman, Bowman, McKenzie, Jeronimo, & Rich, 2009).This study has limitations that should be noted. One limitation is use of self-report, howeverself-report can be reliable with hard-to-reach populations (Darke, 1998) and is arguably themost appropriate way to measure NFOD, since many NFODs are not attended by emergencyservices or police and are therefore not documented elsewhere (Darke, Ross, & Hall, 1996;Dietze, Cvetkovski, Rumbold, & Miller, 2000). Further, we have no reason to believe thatNFODs would be differentially reported by those who were and were not recentlyincarcerated. Second, the binary nature of the outcome – any NFOD in the last six months –means that we under-estimated the incidence of NFOD, because we were unable todetermine how many times a participant had overdosed in this time. Again, we have noreason to suspect that this would selectively impact those who were or were not recentlyKinner et al. Page 6Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author Manuscriptincarcerated. Third, due to limited statistical power we were unable to conduct our analysesseparately for depressant and stimulant overdoses. Although the vast majority of NFODs inboth groups were attributed to depressant drugs (usually heroin), the risk factors forstimulant overdoses may differ, and should be the subject of further investigation. Fourth,our sample was not randomly selected and therefore our findings may not be generalizableto all illicit drug users in Vancouver or elsewhere. A final limitation is that among thoserecently incarcerated, we were unable to confirm that the NFOD occurred after, rather thanbefore, incarceration. However, the markedly elevated incidence of NFOD among thoserecently incarcerated is consistent with evidence of increased incidence of fatal OD afterrelease from custody (Binswanger et al., 2007; Farrell & Marsden, 2008; Kariminia et al.,2007; Merrall et al., 2010; Rosen et al., 2008; Stewart et al., 2004), which suggests that atleast the majority of NFODs among those recently incarcerated occurred after release fromcustody.In summary, among a large, community-recruited sample of illicit drug users this studyidentified a range of modifiable risk factors for NFOD, and found that these risk factorswere similar for those who had and had not experienced incarceration recently. However,the incidence of NFOD was higher among those incarcerated recently, highlighting theurgent need for implementation of evidence-based preventive measures both before releaseand importantly, after return to the community. Further research is required to understandthe causal mechanisms underpinning overdose in ex-prisoners, so that such interventions canbe appropriately targeted and tailored.AcknowledgmentsRole of funding sourcesThe study was supported by the US National Institutes of Health (R01DA011591/R01DA021525) and the CanadianInstitutes of Health Research (RAA-79918/MOP-79297). Stuart Kinner is supported by the Australian NationalHealth and Medical Research Council (1004765/569897). Thomas Kerr is supported by the Michael SmithFoundation for Health Research and the Canadian Institutes of Health Research. M-J Milloy is supported by adoctoral research award from the Canadian Institutes of Health Research. Funding sources had no involvement instudy design; collection, analysis and interpretation of data; drafting the manuscript or submission of themanuscript.The authors thank the study participants for their contribution to the research, as well as current and pastresearchers and staff. 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Page 11Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptKinner et al. Page 12Table 1Descriptive statistics for those who did and did not report recent incarceration at baseline.Recent incarceration No recent incarceration p valueN=686 N=1829n (%) n (%)Mean age in years (range) 35.69 (16.56–56.81) 39.46 (13.26–58.28) <0.0001Female 205 (29.88) 657 (35.92) 0.0045Aboriginal ancestry 200 (29.15) 540 (29.52) 0.8562Married 143 (20.85) 390 (21.32) 0.7941Living alone 349 (50.87) 1013 (55.39) 0.0432Homeless 147 (21.43) 256 (14.00) <0.0001Formal employmenta 104 (15.16) 389 (21.27) 0.0006Daily heroin usea 355 (51.75) 603 (32.97) <0.0001Daily cocaine usea 276 (40.23) 483 (26.41) <0.0001Daily speedball usea 134 (19.53) 159 (8.69) <0.0001Daily methamphetamine usea 16 (2.33) 39 (2.13) 0.7600Daily morphine usea 24 (3.50) 41 (2.24) 0.0769Daily benzodiazepine usea 65 (9.48) 104 (5.69) 0.0007Daily alcohol use >4 drinksa 55 (8.02) 110 (6.01) 0.0707MMT 95 (13.85) 416 (22.74) <0.0001Binge drug usea 318 (46.36) 680 (37.18) <0.0001Public injectinga 224 (32.65) 359 (19.63) <0.0001Injected while incarcerateda 65 (9.48) – –Where incarcerated recentlya Local jail 432 (62.97) – – Provincial prison 236 (34.40) – – Federal prison 18 (2.62) – –HIV seropositive 155 (22.59) 515 (28.16) 0.0049HCV seropositive 580 (84.55) 1487 (81.30) 0.0580Previous imprisonment 682 (99.42) 1316 (71.95) <0.0001Non-fatal overdose Last six months 133 (19.39) 217 (11.86) <0.0001 Ever 397 (57.87) 924 (50.52) 0.0010aIn the last six months.Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptKinner et al. Page 13Table 2Univariate and multivariate analysis of factors associated with non-fatal overdose among individuals who didand did not report recent incarceration.Recently incarcerated Not recently incarceratedOR (95% CI) AOR (95% CI) OR (95% CI) AOR (95% CI)Age Per year older 0.97 (0.96–0.98) 0.98 (0.97–0.99) 0.95 (0.94–0.96) 0.97 (0.96–0.98)Gender Female vs. male 1.14 (0.91–1.44) 1.20 (1.00–1.42)Aboriginal ancestry Yes vs. no 0.89 (0.69–1.13) 0.98 (0.82–1.18) Yes vs. no 1.30 (1.04–1.62) 1.76 (1.44–2.15) 1.31 (1.04–1.64)Formal employmenta Yes vs. no 1.11 (0.85–1.44) 1.00 (0.85–1.18)Marital status Married vs. other 1.04 (0.82–1.31) 0.88 (0.74–1.04)Live alone Yes vs. no 1.12 (0.93–1.35) 1.00 (0.87–1.15)Heroin injectiona ≥Daily vs. less 1.80 (1.48–2.18) 1.29 (1.05–1.59) 2.24 (1.94–2.59) 1.33 (1.14–1.57)Cocaine injectiona ≥Daily vs. less 1.91 (1.59–2.29) 1.49 (1.22–1.83) 2.62 (2.26–3.03) 1.72 (1.47–2.03)Speedball injectiona ≥Daily vs. less 1.75 (1.39–2.22) 2.21 (1.78–2.75)MA usea ≥Daily vs. less 1.78 (1.05–3.03) 1.98 (1.21–3.22) 2.14 (1.38–3.32) 1.97 (1.21–3.19)Morphine usea ≥Daily vs. less 1.01 (0.56–1.83) 1.33 (0.88–1.99)Benzodiazepine usea ≥Daily vs. less 1.96 (1.37–2.81) 1.90 (1.29–2.80) 2.44 (1.92–3.11) 2.11 (1.62–2.75)Alcohol use >4 drinksa ≥Daily vs. less 1.26 (0.91–1.75) 1.40 (1.14–1.71) 1.28 (1.03–1.60)MMT Yes vs. no 0.56 (0.42–0.74) 0.64 (0.48–0.85) 0.45 (0.38–0.55) 0.60 (0.50–0.72)Binge drug usea Yes vs. no 2.02 (1.69–2.41) 1.67 (1.38–2.03) 2.68 (2.35–3.05) 2.09 (1.82–2.40)Public injectinga Yes vs. no 1.64 (1.35–2.00) 1.34 (1.10–1.65) 2.38 (2.01–2.82) 1.46 (1.21–1.76)Where incarcerateda Provincial vs. local 0.89 (0.74–1.07) –Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptKinner et al. Page 14Recently incarcerated Not recently incarceratedOR (95% CI) AOR (95% CI) OR (95% CI) AOR (95% CI) Federal vs. local 0.64 (0.33–1.24) –Previous incarceration Yes vs. no 1.00 (0.65–1.54) 0.73 (0.61–0.88) 0.80 (0.66–0.96)Inject while incara Yes vs. no 1.52 (1.11–2.08) –Previous NFOD Yes vs. no 3.60 (2.77–4.68) 3.87 (2.97–5.03) 3.04 (2.52–3.66) 3.41 (2.83–4.12)HIV-serostatus Positive vs. negative 0.76 (0.59–0.98) 0.77 (0.61–0.99) 0.80 (0.66–0.97)HCV-serostatus Positive vs. negative 1.37 (0.93–2.01) 0.74 (0.57–0.95)aIn the last six months.Addict Behav. Author manuscript; available in PMC 2013 June 01.NIH-PA Author ManuscriptNIH-PA Author ManuscriptNIH-PA Author ManuscriptKinner et al. Page 15Table 3Multivariate analysis of interaction between HIV infection and age, among those recently incarcerated.HIV serostatus Age (median split) AORa 95% CI p valueNegative ≤38 years 1.00 Ref. Ref.Negative >38 years 0.74 0.58–0.95 0.0180Positive ≤38 years 0.65 0.47–0.88 0.0053Positive >38 years 0.70 0.48–1.02 0.0639aAdjusted for daily use of heroin, cocaine, methamphetamine and benzodiazepines; MMT; binge drug use; public drug use; previous NFOD.Addict Behav. Author manuscript; available in PMC 2013 June 01.


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