The Cedar Project: risk factors for transition to injection drug use among young, urban Aboriginal people.

Background: Studies suggest that Aboriginal people in Canada are over-represented among people using injection drugs. The factors associated with transitioning to the use of injection drugs among young Aboriginal people in Canada are not well understood.

Methods: The Cedar Project is a prospective cohort study (2003-2007) involving young Aboriginal people in Vancouver and Prince George, British Columbia, who use illicit drugs. Participants' venous blood samples were tested for antibodies to HIV and the hepatitis C virus, and drug use was confirmed using saliva screens. The primary outcomes were use of injection drugs at baseline and tranisition to injection drug use in the six months before each follow-up interview.

Results: Of 605 participants, 335 (55.4%) reported using injection drugs at baseline. Young people who used injection drugs tended to be older than those who did not, female and in a relationship. Participants who injected drugs were also more likely than those who did not to have been denied shelter because of their drug use, to have been incarcerated, to have a mental illness and to have been involved in sex work. Transition to injection drug use occurred among 39 (14.4%) participants, yielding a crude incidence rate of 19.8% and an incidence density of 11.5 participants per 100 person-years. In unadjusted analysis, transition to injection drug use was associated with being female (odds ratio [OR] 1.98, 95% confidence interval (CI) 1.06-3.72), involved in sex work (OR 3.35, 95% CI 1.75-6.40), having a history of sexually transmitted infection (OR 2.01, 95% CI 1.07-3.78) and using drugs with sex-work clients (OR 2.51, 95% CI 1.19-5.32). In adjusted analysis, transition to injection drug use remained associated with involvement in sex work (adjusted OR 3.94, 95% CI 1.45-10.71).

Interpretation: The initiation rate for injection drug use of 11.5 participants per 100 person-years among participants in the Cedar Project is distressing. Young Aboriginal women in our study were twice as likely to inject drugs as men, and participants who injected drugs at baseline were more than twice as likely as those who did not to be involved in sex work.