HIV transmission has effectively been reduced in many countries by focusing on high transmission foci with interventions tailored to key populations groups and high risk behaviours. However people who inject drugs (PWID) still accounted for significant proportions of new HIV and Hepatitis C infections in several regions in 2014 . Among PWID, as in other populations, risk behaviours are not distributed equally. Polydrug use (using multiple drugs) in particular has increasingly been cited as a source of harm and possibly greater HIV infection risk but remains under-researched. In this thesis, I assessed the epidemiological significance of polydrug use on HIV and HCV risk behaviours among PWID, using several methods, and data sources from different settings. Multiple methodological challenges were faced, related to inherent difficulties in studying PWID, including stigmatised behaviours, comparatively small sample sizes and the absence of sampling frame for PWID. I established that polydrug use was frequent among PWID, in contrast with the common assumption that PWID mainly inject heroin, and considerable proportions of injectors across locations had recently injected or used multiple drugs (chapter 2). I generated new evidence on the biological and behavioural risks associated with injecting certain drugs and drug combinations in three stages. First, in the meta-analysis, HIV incidence rates were consistently higher among PWID injecting cocaine, amphetamine (ATS) or combinations of heroin and stimulants, compared to those not injecting or not injecting the drug(s). Wide confidence intervals and inconsistent reference categories however, limited conclusions (chapter 3). Second, I identified differences in injecting risk and HIV status between ATS and opiate injectors (chapter 5), and greater injecting and sexual risk among polydrug- than single-drug injectors in Russia and Estonia (chapter 6). Finally, using a generic polydrug typology developed in latent variable modelling, I found significant differences in HIV-related injecting and sexual risk behaviours between polydrug classes (chapter 7). The results of this work fill important research gaps by establishing that polydrug use is frequent and associated with substantial heterogeneity in HIV risk among PWID. My thesis examines the implications of these findings and proposes a polydrug use typology to help tailor drug and HIV prevention and treatment interventions to high risk PWID sub-groups to prevent the spread of new HIV and HCV infections.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:733115 |
| Date | January 2016 |
| Creators | Tavitian-Exley, Isabel |
| Contributors | Boily, Marie-Claude ; Maheu-Giroux, Mathieu |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/55175 |
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