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Homelessness & Health in Canada

 | 
Manal Guirguis-Younger
, 
Ryan McNeil
, 
Stephen W. Hwang

Part II-Policy & Programmatic Responses to Homelessness & Health

Chapter 6. Housing and HIV/AIDS among People Who Inject Drugs: Public Health Evidence for Effective Policy Response

Brandon D. L. Marshall et Thomas Kerr

Texte intégral

Introduction

1Injection drug use is a serious public health concern in many countries, including Canada. Recent estimates suggest that between 220,000 and 375,000 Canadians, or approximately 1 to 2 percent of the general population, have ever injected an illegal drug (Mathers et al. 2008). People who inject drugs (injection drug users or idu) represent a diverse population with a range of health needs and outcomes. In Canada, the majority of idu are male, and persons of Aboriginal ancestry are heavily overrepresented among idu (phac 2006). Initiation into injection drug use typically occurs at 20 years of age (Ompad et al. 2005); however, a significant proportion of idu report beginning injecting in their early teens (Miller et al. 2006). Although the pathways into injection drug use are varied, heavy non-injection drug use and homelessness in the months preceding injection onset are common (Roy et al. 2003). Further, several recent studies (Kerr et al. 2009; Ompad et al. 2005) have pointed to the role that childhood maltreatment plays in increasing the risk of initiating injection drug use.

2Prior to the discovery of hiv in 1982, very little research involving idu had been conducted in Canada. However, injection drug use was prevalent across the country well in advance of the hiv pandemic. Historical documents suggest that by the mid-20th century, 4,000 Canadians were actively injecting drugs: the vast majority of these early users were from poor working-class families living in the cities of Vancouver and Toronto (Carstairs 2002). By 1989, 120 aids cases attributable to injection drug use had been reported to the Federal Centre for aids, and high rates of hiv-related risk behaviour among idu began to garner significant public health attention (Smart 1991). In the same year, studies presented at the 5th International aids Conference in Montreal provided further evidence that immediate public health action was required to prevent the situation from worsening (Bruneau et al. 1989). An early study undertaken in Montreal suggested that the prevalence of hiv among idu was approximately 4 percent (Lamothe et al. 1988). In 1997, a massive hiv epidemic, described as one of the most severe in the developed world, was observed among idu in Vancouver (Strathdee et al. 1997). In more recent years, the proportion of hiv infections attributable to injection drug use has remained relatively constant at just under 20 percent, representing between 390 and 750 new cases of hiv infection annually (phac 2009). In addition to a sustained and unacceptably high rate of hiv incidence, idu face multiple social and structural barriers to accessing appropriate hiv treatment and experience poorer clinical outcomes (Wood et al. 2008).

Homelessness and the Risk Environment

3The limited success of conventional public health interventions to reduce hiv-related morbidity and mortality among idu has led to a new emphasis on ecological approaches that incorporate how factors exogenous to the individual impact exposure to risk and poor health. For example, the 'risk environment' model posits that social, physical and structural factors intersect to produce differential exposures to infectious disease risks and drug-related harms (Rhodes et al. 2005). These environments thus impose constraints on one's ability to mitigate risk behaviour and achieve health. Within this framework, substandard housing and homelessness have been identified as key factors that play direct roles in augmenting vulnerabilities to hiv and perpetuating health inequities among marginalized populations (Galea and Vlahov 2002). Complementary to this body of literature is a large volume of research indicating that secure and stable housing is a robust determinant of health within the general population (Hwang 2001).

4Despite evidence to suggest a powerful link between lack of access to housing, hiv infection and overall health, there remains no clear policy approach to addressing housing and hiv/aids issues in Canada (Canadian aids Society 2009). Although research has shown that housing plays an important and direct role in the prevention of hiv and other health-related harms among idu (Briggs et al. 2009), policy-makers in Canada have failed to implement housing interventions as central tenets of current hiv/aids strategies for this population. In order to more effectively influence the development of evidence-based policy and programs that benefit equivocally housed drug users, scientists, policy-makers and service providers must promote rigorous housing-focused research, articulate why housing and hiv/aids issues are closely linked and justify how the provision of supportive housing can improve the health of drug users living with hiv/aids (Aidala and Sumartojo 2007).

5This review synthesizes evidence, primarily from a Canadian context, examining the relationship between housing and hiv/aids among idu populations, compares housing interventions to reduce hiv risk behaviour and support individuals who are already living with hiv/aids and provides recommendations for future research to best inform the development of housing policy. Given the recent call to action by the Canadian aids Society to address housing as a critical component of the federal response to hiv/aids in Canada (Canadian aids Society 2009), this chapter aims to serve as a key tool for public health practitioners and other stakeholders interested in advocating for evidence-based housing interventions to improve the health of people who inject drugs.

Housing and HIV/AIDS among Drug Users

6Homeless people in Canada face significant barriers to accessing health and social services and experience a range of adverse health outcomes (Hwang 2001). Notably, homelessness is a strong predictor of premature mortality (Hwang 2000). Homelessness is extremely common among people who inject drugs, particularly those who are hiv positive (Song et al. 2000). An inability to attain safe and stable housing is known to be both a cause and consequence of drug use (Galea and Vlahov 2002). For example, studies of homeless young people have shown that drug use is often a critical factor in deciding to leave home, while many youth initiate illicit drug use only after becoming homeless (Mallett, Rosenthal and Keys 2005). It is clear that chronic homelessness tends to exacerbate the negative consequences of drug use (and vice versa), which can result in a mutually reinforcing pattern of complex service needs and declining overall health (Neale 2001). Therefore, elucidating how homelessness, drug use and hiv/aids intersect to produce and perpetuate health inequities is crucial for informing more effective public health strategies to address the needs of this marginalized population.

7Housing environments shape and perpetuate hiv risk among people who inject drugs (Aidala et al. 2005). Many studies have demonstrated that homeless idu are more likely than housed individuals to participate in sexual and injecting-related hiv risk behaviour, including syringe sharing, shooting gallery attendance and sex work (Coady et al. 2007; Des Jarlais, Braine and Friedmann 2007; Reyes et al. 2005; Salazar et al. 2007). Furthermore, homeless idu are more likely to report higher intensity drug use patterns than those with stable housing (Lloyd-Smith et al. 2009), while higher levels of sexual risk have been observed among drug-using youth who are equivocally housed (Marshall et al. 2009). Among young drug users, hiv risks tend to accumulate as the severity and frequency of homelessness increases, indicating a dose-response relationship between hiv vulnerability and exposure to street environments (Ennett et al. 1999). Similarly, residential transience and long-term housing instability are important drivers of hiv risk among drug-using adults. Injection risk behaviours are more common among adult idu who report frequent moves (German, Davey and Latkin 2007). Frequent relocation may also disrupt social networks and diminish one's exposure to positive peer norms, which have been shown to be important mitigating factors of risk behaviour among idu (Latkin et al. 2003). Finally, unstable housing and homelessness have been identified as key determinants of poor treatment outcomes among hiv-positive idu (Knowlton et al. 2006).

8Given the strong and consistent relationship between inadequate housing environments and hiv risk behaviour, it is not surprising that several studies have identified an independent association between poor housing conditions and increased rates of hiv infection among idu. One of the earliest studies to demonstrate this link was conducted in Ohio, and although the overall hiv prevalence was low (1.5%), living in a homeless shelter residence was second only to being a man who has sex with men as the strongest correlate of hiv infection (Siegal et al. 1991). A more recent study conducted in Baltimore also observed a strong relationship between exposure to homelessness and both hiv prevalence at baseline and seroconversion over follow-up (Song et al. 2000). In Canada, a large prospective cohort study of injection drug users in Vancouver (i.e., the Vancouver Injection Drug Users Study) has investigated the relationship between housing status and hiv among idu for over a decade. hiv infection was more common among idu reporting recent homelessness or unstable living conditions at baseline, independent of other risk factors including sex work and syringe sharing (Strathdee et al. 1997). A follow-up study indicated a strong association between unstable housing and hiv incidence (Tyndall et al. 2003). This trend has continued: after eleven years of follow-up, housing status has remained a significant predictor of hiv seroconversion (see Figure 6-1).

Figure 6-1. Cumulative incidence of HIV infection among Vancouver injection drug users from 1996 to 2007, stratified by housing status at baseline
Note: Unstable housing includes living in a shelter/hostel, treatment/recovery house, jail, singleroom occupancy hotel or on the street. Stable housing was defined as living in an apartment or house.
Source: Urban Health Research Initiative, British Columbia Centre for Excellence in HIV/AIDS (2009)

Homelessness and the Production of HIV Risk

9Detailed ethnographic investigations have established the importance of place in the social-structural production of hiv risk among homeless idu populations. For example, participant-observation studies have shown how homelessness and the extreme social marginalization experienced by many idu result in survival strategies in which precarious income-generating activities and social relationships of mutual dependence are prioritized over hiv risk reduction practices (Bourgois 1998). Among women, homelessness also exacerbates exposure to everyday violence and subordinated positions in social hierarchies, in which the risk of hiv infection is secondary to immediate physical dangers (Epele 2002).

10Ethno-epidemiological studies have also suggested that a multitude of environmental and structural factors may explain the observed relationship between housing instability and hiv vulnerabilities. For example, homeless idu experience increased exposure to high-risk injecting environments (e.g., shooting galleries, open drug scenes), which have been shown to be settings of heightened hiv vulnerability, particularly for younger idu (Rhodes et al. 2006). Homeless idu who inject in public settings are also more likely to skip safer injecting practices due to fears of being intercepted by the police, physically assaulted or robbed (Small et al. 2007). Furthermore, homeless idu frequently encounter police as a result of participation in illegal income-generating activities and are thus more likely to experience hiv risks associated with incarceration (Wood et al. 2005). At a policy level, features unique to unstable housing environments have also been shown to perpetuate hiv risks among idu. For example, evening 're-entry fees', a common feature of single-room occupancy hotels, dissuade individuals from accessing hiv prevention and harm reduction services (Wood and Kerr 2006b) and thus may be partially responsible for the high prevalence of hiv observed among persons who live in these environments (Shannon et al. 2006).

Barriers to Housing

11idu experience a multitude of social and structural barriers while attempting to access safe and stable housing. Many idu are considered by housing providers as 'hard to house' for reasons including lack of stable employment and income, 'unclean' visual appearance, erratic or aggressive behaviour and the presence of co-morbidities (e.g., mental illness) associated with chronic substance use (Gurstein and Small 2005). Having a criminal history and experiencing incarceration, common among idu, further complicates one's ability to obtain housing (Mizuno et al. 2009). Furthermore, individuals who are actively drug dependent and continue to use substances are often ineligible for abstinence-contingent housing services or will be discharged upon relapse or positive urine test (Kruas, Serge and Goldberg 2006). For many drug-using youth, the fact that many shelters are abstinence focused and adhere to a 'zero-tolerance approach' severely restricts acceptable housing options (Krüsi et al. 2010).

12The ability to obtain stable housing is further complicated by inadequate access to substance abuse treatment, income support and employment opportunities. For example, idu who are homeless are less likely to enrol in any form of addiction treatment (Wood et al. 2005) and are less likely to attain legal employment (Richardson et al. 2008) compared to those who are stably housed. Furthermore, unstable housing status has been associated with a decreased uptake of methadone maintenance therapy (mmt) among opioid users in Canada (Fischer et al. 2008). Homelessness has also been found to impact the types of addiction treatment most often accessed by people who inject drugs. A large study conducted in Massachusetts demonstrated that homeless idu were more likely to enter detoxification and residential treatment programs but were half as likely to access mmt over the four-year study period (Lundgren et al. 2003). These short-term programs often do not lead to improved long-term housing outcomes due to a lack of integration between substance abuse treatment and housing services, insufficient or unacceptable housing options and other gaps in the continuum of care (Meschede 2010).

Housing as HIV/AIDS Prevention, Treatment and Care

13Housing programs are increasingly well recognized as an integral component of comprehensive hiv prevention strategies (Shubert and Bernstine 2007). In the United States, observational studies and randomized controlled trials have demonstrated that the provision of rental assistance and other housing supports is associated with improved health outcomes and better treatment adherence among persons living with hiv/aids (plwha) (Wolitski et al. 2010). Among homeless plwha, treatment compliance is complicated by competing priorities associated with homelessness (e.g., obtaining shelter, meeting dietary requirements), lack of transportation to hiv-related health care services and inability to store medications (Henry et al. 2008). The advent of single-pill regimens will likely mitigate many of these concerns, although the provision of housing should continue to be a key priority to improve hiv-related outcomes and overall health among idu. Even with less than perfect adherence, homeless plwha have been shown to benefit from hiv treatment; thus, service providers should not restrict access to highly active antiretroviral therapy (haart) on the basis of housing status alone (Wolitski, Kidder and Fenton 2007). Finally, given the evidence indicating that housing instability significantly reduces one's ability to engage effectively with hiv treatment and practice risk reduction behaviours, secondary prevention programs for plwha at risk for hiv transmission should include housing assistance within a package of comprehensive intervention strategies (Fisher and Smith 2009). hiv-infected persons with unsuppressed viral load (i.e., detectable levels of virus circulating in body fluids) are more likely to transmit hiv during high-risk sexual or injection-related behaviours (Attia et al. 2009). Higher levels of hiv viral load among idu have also been associated with increased hiv incidence at the community level (Wood et al. 2009). Given that antiretroviral therapy induces viral load suppression among adherent patients (Gulick et al. 1997), the expansion of access to haart is now thought to be an effective means to control the spread of hiv (Montaner et al. 2006). However, hiv-infected idu who are homeless are less likely to achieve viral load suppression upon receiving haart (Knowlton et al. 2006). Therefore, if idu populations are to receive maximal treatment and preventive benefits of haart expansion programs, efforts should also be made to address housing instability and other barriers to treatment initiation and compliance. Under this framework, safe and stable housing are viewed not only as a necessary prerequisite to effective hiv/aids management and care but also as an evidence-based public health intervention to reduce new hiv infections among drug users.

Evidence-Based Interventions

14Several interventions and models of housing assistance programs have been proposed for drug-using individuals who are homeless or are at risk for homelessness. In this section, we provide a brief discussion of several housing interventions and a review of evidence regarding the effectiveness of each program.

Case Management

15Case management has been found to facilitate access to stable housing and improve adherence and other treatment outcomes among homeless and marginally housed drug users with hiv infection (Kushel et al. 2006). Furthermore, the provision of case management can prevent individuals undergoing substance abuse treatment from relapsing and becoming unstably housed (Katz et al. 2001). However, evidence suggests that better long-term housing outcomes are achieved with more comprehensive housing support services compared to case management alone (Clark and Rich 2003). For these reasons, case management in the absence of other comprehensive interventions is not recommended as a best practice to achieve sustainable housing among people who use drugs.

Linear Approach Programs

16In the United States, linear approach programs (also called the 'continuum of care' model) are common and provide housing once an individual has completed a course of addiction treatment and has achieved abstinence (Milby et al. 2000). These programs have demonstrated efficacy in some settings, and sustained periods of abstinence have been demonstrated among individuals who achieve abstinent-contingent housing (Schumacher et al. 2007). However, many of these programs fail to recognize the chronic nature of substance abuse and thus are unable to provide appropriate support upon relapse. For example, individuals who do return to drug use after obtaining housing may be evicted, thus dramatically increasing the risk for homelessness and return to engagement in hiv risk behaviours.

17A second limitation of this type of intervention is that a lack of formal linkages with placement programs and low rental stock may prevent individuals who achieve abstinence from obtaining affordable stable housing. This has been demonstrated recently by a Vancouver study showing that enrolment in addiction treatment failed to predict obtaining stable housing over four years of follow-up (Palepu et al. 2010). Improved integration of addiction treatment services with supportive housing programs for individuals who are able to maintain abstinence and those who continue drug use or experience relapse is therefore recommended.

Housing First

18A more recent model is 'Housing First', premised on the notion that housing is a basic human right and should not be requisite to abjuring substance use. Within a Housing First framework, homeless individuals with substance abuse or other co-morbidities (e.g., mental illness) are immediately provided with their own apartments without any prerequisites for treatment or sobriety (Greenwood et al. 2005). Thus, individuals are not required to be in substance abuse treatment in order to obtain or maintain housing. In addition to the provision of housing, these models often include additional support services that participants can access at their discretion, including an 'Assertive Community Treatment' team consisting of health care and social service professionals, for example (Tsemberis, Gulcur and Nakae 2004). The underlying principle of this approach is one of 'consumer choice'; that is, participants are empowered to determine the priority and order of services they receive.

19Housing First programs have been shown to result in higher rates of housing stability compared to individuals receiving abstinence-contingent services and do not lead to increases in substance use among participants (Tsemberis, Gulcur and Nakae 2004). Housing First interventions have also been shown to be highly cost effective for chronically homeless persons with severe alcohol dependence (Larimer et al. 2009). These programs have also been strongly endorsed by the Canadian Mortgage and Housing Corporation (cmhc) as the preferred mode of housing homeless individuals with substance abuse or dependence. In a review of housing programs in Canada, cmhc (2006) concluded that the immediate provision of safe, independent and secure housing is one of the key factors in assisting individuals to reduce drug use and the negative health impacts of substance abuse on their lives.

20Harm reduction approaches provided in combination with permanent, independent housing are an effective means to address the needs of homeless people with substance abuse and are thus a central tenet of the Housing First model (Tsemberis, Gulcur and Nakae 2004). Harm reduction refers to policies and practices that aim to reduce the risks and harmful effects associated with substance use without requiring reduced drug consumption or abstinence (Inciardi and Harrison 2000). In Canada, some housing programs have adopted a 'client-centred' harm reduction approach, which focuses on supporting individuals in meeting their housing, substance abuse and health care needs in a flexible, respectful and dignified way (Evans and Strathdee 2006). The provision of housing is increasingly viewed internationally as an evidence-based harm reduction strategy to reduce risk behaviour and prevent adverse health outcomes among people who inject drugs (Briggs et al. 2009). Evidence also exists to suggest that idu who achieve stable housing are more likely to cease injection drug use altogether and are less likely to relapse (Shah et al. 2006). These findings provide further support for Housing First models and suggest that the immediate provision of housing should be regarded as an evidence-based pathway to drug use cessation.

Recommendations for Research and Policy

21Throughout this chapter we have argued that housing is good for health. This is particularly true for marginalized people who are equivocally housed and use drugs. The benefits of housing in terms of hiv prevention are clear: a large volume of evidence indicates that safe and stable housing is associated with reduced engagement in hiv risk behaviour and improved health outcomes for those living with hiv disease. In order to more effectively inform housing and health policy in Canada, researchers must now do more than simply state that these relationships exist. Novel lines of inquiry should be proposed and examined; for example, evidence that differentiates which modes of housing interventions are most successful at improving the health of homeless people who use drugs would be invaluable for the design and implementation of new housing programs. Examining these 'second generation' questions is only a very recent phenomenon and thus many questions remain unanswered. Although an increasing number of researchers are investigating the effectiveness of the integration of housing and addiction treatment services based on Housing First and harm reduction models, case studies of success, particularly in the Canadian context, are urgently needed. One example is the Dr. Peter Centre in Vancouver, which has successfully integrated an assisted-living residential program for hiv-positive idu with harm reduction approaches, including a supervised injecting room and spaces where residents can consume non-injection drugs such as crack cocaine (Krüsi et al. 2009). The evaluation of innovative models of care for homeless people who use drugs is critical for the creation of evidence-based housing programs across the country.

22It must be recognized that additional scientific evidence is on its own insufficient to enact the policy and programmatic changes that would often be required to meaningfully improve the health of homeless idu. Controversial interventions (even those with a significant scientific evidence base such as needle exchange programs) can be met with moral and ethical arguments that in some cases have impeded their implementation and expansion (Buchanan et al. 2003). Acknowledging moralistic opposition to harm reduction-based approaches and identifying ways to engage communities and policy-makers that hold these views is critical to ensuring that future interventions are based upon the best available scientific evidence.

23A second area of future research is the identification of points of intervention to most effectively bring homeless idu in contact with the health and social service systems. Given that idu are an extremely marginalized population who experience a multitude of barriers to accessing traditional primary and ancillary services (Wood and Kerr 2006a), housing programs should provide multiple points of entry and be highly flexible to diverse health needs and challenges. For example, although many idu are completely disconnected from services, those who are unstably housed report high rates of emergency room and acute care utilization (Kerr et al. 2005). These points of contact with the primary health care system may be an important opportunity to engage and connect homeless idu with low threshold housing support programs. The responsibility lies with service providers to identify these opportunities and with researchers to evaluate their potential to improve the health and functioning of people who use drugs.

24Finally, given recent Canadian research suggesting that the use of non-injection drugs (e.g., crack and methamphetamine) among marginalized groups may be associated with elevated hiv risk (Bungay et al. 2010; DeBeck et al. 2009), future studies should seek to elucidate the intersection of homelessness and non-injection drug use in the production of hiv-related risks and harms. Importantly, there are few effective treatments for stimulant dependence (Rawson et al. 2006), and few studies have determined whether the provision of housing may improve treatment outcomes among these groups. It is clear, however, that the creation of sustainable supportive housing for non-injection drug users should be a policy and public health priority.

25We wish to conclude this chapter by emphasizing that the implementation of housing interventions should proceed in tandem with improved access to and expansion of comprehensive hiv services. Indeed, it is the integration of housing and homelessness prevention programs with addiction treatment, hiv treatment, health services and other hiv prevention interventions where the largest benefits to the individual and to society will likely be observed. It is our hope that this chapter will act as a call to researchers, service providers and advocates to better articulate the need for housing to assume a central role in Canadian public health strategies to improve the health of all citizens, including those who use drugs.

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Table des illustrations

Légende Figure 6-1. Cumulative incidence of HIV infection among Vancouver injection drug users from 1996 to 2007, stratified by housing status at baselineNote: Unstable housing includes living in a shelter/hostel, treatment/recovery house, jail, singleroom occupancy hotel or on the street. Stable housing was defined as living in an apartment or house.Source: Urban Health Research Initiative, British Columbia Centre for Excellence in HIV/AIDS (2009)
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Auteurs

Assistant Professor in the Department of Epidemiology at the Brown University School of Public Health. Dr. Marshall completed his doctoral degree in epidemiology at the University of British Columbia School of Population and Public Health and postdoctoral training in the Department of Epidemiology at the Columbia University Mailman School of Public Health. His research interests focus on substance use epidemiology and the social, environmental and structural determinants of health among vulnerable populations

Director of the Urban Health Research Initiative at the British Columbia Centre for Excellence in hiv/aids and an Associate Professor in the Faculty of Medicine at the University of British Columbia (Division of aids). Dr. Kerr has extensive research experience in the areas of health psychology, behavioural science, community-based research and public health, especially in evaluating programs and treatments designed to address addiction, injection drug use and hiv/aids

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