This study examined the association between solvent use in Aboriginal IDU and socio-demographic factors, drug-related risk factors, use of other illicit substances and BBP infection. We found that after adjusting for other variables including sex, solvent use was significantly associated with Talwin & Ritalin injection, HCV status and age in this population.
Some important limitations of the study should be stated at the outset. First and foremost, ours was a cross-sectional study, and a causal linkage between solvent use and injection drug use cannot be inferred from the data. Although both likely share determinants, our data are insufficient to establish causality. Aboriginal individuals in Canada face a combination of socially and structurally determined vulnerabilities, including high rates of entrenched poverty, unemployment, homelessness and sexual and physical abuse[2, 52, 53]. Many of these factors stem from a history of colonization, oppression, systemic racism and discrimination in Canadian society and have resulted in Aboriginal Canadians having unequal access to a variety of resources [2, 54]. Thus, the perniciousness of both solvent and injection drug use within Aboriginal populations is more likely a result of these determinants. Second, solvent use was measured broadly. The measure used was not precise enough to discriminate between chronic and casual use. Similarly, different types of solvents were not captured in this study. Third, since a sampling frame was not possible to construct for this marginalized and hidden population, the sample was not randomly generated and may not be representative of Aboriginal IDUs in other settings, or in Winnipeg. Fourth, social desirability bias, or high non-response rate is always an issue with self-reported data; however, it is likely that this would have served to underestimate associations toward the null. Finally, the sample size was relatively small and thus may have not had power to detect significant findings.
Previous studies in Winnipeg have reported Talwin & Ritalin injection as being strongly associated with both Aboriginal ethnicity[50, 55] and high HCV prevalence. That HCV infection is three times more likely in the population of solvent-using Aboriginal IDU, after controlling for Talwin & Ritalin injection and risky injection practices, strongly suggests the existence of pockets of higher risk even amongst an already high-risk subpopulation[39, 47]. It was also demonstrated that these qualitatively distinct 'higher-risk' groups can be distinguished when both injectable and non-injectable drug use is considered.
The relatively low prevalence of both HIV and HCV among IDU in our geographic setting has motivated researchers to ask what role, if any, public health responses in Winnipeg may have contributed to lower prevalence. Both HIV and HCV prevalence in the subset of solvent-using IDU are relatively higher than other IDU in our sample; and at 18% and 81% respectively, are in closer alignment with the prevalence observed in other jurisdictions[57, 58]. This dichotomy in prevalence reinforces the exceptionally high risk faced by solvent-using IDU, and their real or potential ability to be missed by what otherwise may be an effective public health response. This higher-risk group is particularly relevant given the recent attention paid to especially high rates of HIV in Aboriginal populations in central Canada[11, 12], and serve to illustrate that BBP epidemics in Canada are not homogeneous.
Solvent use is an issue where there are no easily-identifiable solutions[23, 24]. Solvent users are at the bottom of a drug-using hierarchy, in terms of perception by other substance users and practitioners, and by the sheer volume of their social and personal challenges[29, 39, 42, 47]. Thus, given the already difficult lifestyle and behavioural issues related to injection drug use[58, 59], a combination of solvent use and injection drug use within Aboriginal populations may present considerable, and specific challenges for treatment[39, 47]. For example, although there is well-established literature on the effectiveness of harm-reduction efforts such as needle-exchange programs in curtailing the spread of BBPs[60, 61], the constituents of an equivalent and appropriate harm reduction strategy for solvent users have not been well articulated in the literature , although practical advice may include using solvents in groups, and using clean rags or sponges. As well, outreach efforts to these populations may be unduly hampered by the considerable stigma attached to chronic solvent use. Similar to recent Canadian research demonstrating that IDU who also smoked crack cocaine were at higher risk of HIV seroconversion, perhaps an especially chaotic lifestyle is contributing to the higher HCV prevalence in our solvent-using subpopulation.
Understanding outlier populations
As Kuller has suggested that understanding epidemics in "outlier" populations may have substantial benefits in unpacking transmission dynamics in more mainstream populations, a deeper examination of this, and similar subpopulations is warranted. Thus, we submit that understanding the exogenous factors that contribute to solvent use in IDU may result in better understanding of marginalized subpopulations in general, particularly with respect to understanding the trajectory of use. For example, it has been recognized that solvent use is typically a group activity[23, 24, 26]. The natural consequence is the tendency to form closed networks, in this case comprised of fellow solvent-using IDU. This may be particularly true in our study population of Aboriginal IDUs, since individuals have been shown to form more cohesive structures according to ethnicity. At the same time, the near ubiquity and accessibility of sources of solvents and inhalants is clearly a key contributor to their abuse. Recent programs that seek to address solvent use in adolescent Aboriginal Canadians through improving individual-level coping strategies recognize that without multi-level support structures (e.g. family, community, environment) in place, individual recovery is likely to fail. Other researchers have found that strong peer group sanctions against solvent use, in concert with messages concerning the dangers of solvent use were protective against lifetime and current use of solvents. Thus, finding ways to identify and engage with solvent users and their peers may have application with other hidden and marginalized populations. Along this line, some authors have suggested that solvent use may be a marker for an inherently more challenging type of substance user[19, 45]. Thus, it may be useful to understand to what extent the actual choice of solvent use is a proxy for characteristics that distinguish the most marginalized of subpopulations. Understanding the populations that become chronic abusers of easy-to-obtain substances (such as solvents) may help to facilitate a more general understanding of subpopulations that have proven to be intractable to treatment.
The fact that solvent use clusters around Talwin & Ritalin injection suggests two other interesting areas for future research. First, other authors have demonstrated the advantages of understanding IDU from a poly-injection drug use perspective. Here, we have demonstrated the practicality of examining IDU in their use of both injection and non-injection drugs. At the treatment level, this perspective highlights the importance of treating two or more qualitatively distinct addictions concurrently[68, 69]. For example, Stenbacka et al. demonstrated that opiate-injecting IDU undergoing methadone maintenance therapy (MMT) were more likely to relapse if they had co-occurring alcohol abuse issues. Secondly, the clustering of solvent and Talwin & Ritalin use suggests that the use of either is driven, to a certain degree, by opportunism. Although our data cannot provide a definitive answer, it would be useful to know under what circumstances IDU resort to inhaling solvents. Assuming inhalation is their 'fallback' method, and philosophically similar to MMT, perhaps a reliable supply of other injectable or non-injectable drugs would deter this subpopulation of IDU from using solvents, and thus prevent some of the more serious neurological and cognitive deficits associated with long-term chronic use[70, 71].