Elevated HIV risk behaviour among recently incarcerated injection drug users in a Canadian setting: a longitudinal analysis

Background: While incarceration has consistently been associated with a higher risk of HIV infection for individuals who use injection drugs (IDU), the effect of incarceration on the post-release risk environment remains poorly described. We sought to assess the impact of incarceration on risk factors for HIV infection after release from prison in a sample of active IDU in Vancouver, Canada. Methods: Using a prospective cohort of community-recruited IDU followed from May 1, 1996 to November 30, 2005, we examined contingency tables and performed linear growth curve analyses to assess changes in the prevalence of independent risk factors for HIV infection from before to after a period of incarceration among participants reporting incarceration and a matched control group. Results: Of the 1603 participants followed-up over the study period, 147 (9.2%) were eligible for an analysis of post-incarceration risk behaviours and 742 (46.3%) were used as matched controls. Significant differences were found in one or both groups for the prevalence of frequent cocaine injection, requiring help injecting, binge drug use, residence in the HIV outbreak epicentre, sex-trade participation and syringe sharing (all p < 0.05) after incarceration. In linear growth curve adjusted for age, gender and ethnicity, syringe sharing was significantly more common in those recently released from prison (p = 0.03) than in the control group. Conclusion: In a sample of Canadian IDU, we did not observe any effect of incarceration on the prevalence of several behaviours that are risk factors for HIV infection, including intensity of drug use or participation in the sex trade. However, those recently released from prison were more likely to report syringe sharing that those in a matched control group.