Smoking of crack cocaine as a risk factor for HIV infection among people who use injection drugs
October 27, 2009
This paper examined whether use of crack cocaine has become a risk factor for HIV infection. Smoking of crack cocaine was found to be an independent risk factor for HIV seroconversion among injection drug users. This finding points to the urgent need for evidence-based public health initiatives targeted at people who smoke crack cocaine. Innovative interventions that have the potential to reduce HIV transmission in this population, including the distribution of safer crack kits and medically supervised inhalation rooms, need to be evaluated.
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In this prospective study involving participants in the Vancouver Injection Drug Users Study who were HIV negative at enrolment, we found that smoking of crack cocaine became increasingly prevalent over time. We also observed that such use of crack cocaine became an independent risk factor for HIV seroconversion over time after adjusting for potential confounders. This finding suggests that there may be unmeasured risk factors related to the smoking of crack cocaine, or unmeasured confounding factors related to HIV infection.
With respect to unmeasured risk factors, crack cocaine is often smoked with the use of metal or glass pipes, which is known to produce wounds in and around the mouth. These wounds may make people who smoke crack more vulnerable to HIV transmission during activities such as oral sex or sharing of crack pipes. We were unable to evaluate these possible risk factors, however, because the Vancouver Injection Drug Users Study did not investigate the occurrence of oral wounds or the sharing of crack pipes. With respect to possible unmeasured confounders, smokers of crack cocaine may have more HIV-positive individuals in their social networks. Therefore, any sexual or injection risk behaviour would represent an increased likelihood of HIV infection. Again, our study is limited by the inability to assess for this explanation. Finally, there may have been differential recall of HIV risk behaviour because of the psychological effects of crack cocaine. Individuals may have taken risks (e.g., unsafe sex) during binges of crack cocaine use that they did not recall when subsequently surveyed as part of the cohort study.
Although highly controversial, innovative public health programs that address the unique needs of people who smoke crack cocaine and that contribute to HIV prevention efforts may include the distribution of safer crack kits6 and the provision of supervised inhalation rooms. In previous studies, drug users have reported a strong willingness to use the equipment provided in safer crack kits. Early evaluations have found this strategy to be associated with reductions in sharing smoking equipment. Although the provision of an inhalation room may be even more controversial, this strategy has been successfully implemented in several European settings. Feasibility studies in Vancouver showed a strong willingness among local smokers of crack cocaine to use such a facility. Inhalation rooms and the distribution of safer crack kits also afford the opportunity for health workers to engage with people who smoke crack. Such encounters may be critical for initiating efforts to address some of the needs for health care, social assistance and referral for addiction treatment of this often hidden population.