Objectives: To determine the temporal trends of initiation into injection drug use, current injection, and recent receptive sharing of injection paraphernalia among street youth.
Design: Data from two cohort studies conducted between 1995 and 2005 were combined.
Methods: Recruitment was done on an ongoing basis. Interviews were performed semi-annually. Overall and annual drug injection incidence rates were calculated with the person-time method. Poisson regression was used to assess the predictive power of calendar year on incidence rate. Generalized estimating equations (GEE) were used to assess linear trends in current injection among street youth and in recent receptive sharing of syringe and other injection paraphernalia among current injection drug users.
Results: By 31 March 2005, 1633 subjects had completed 8875 questionnaires. Most subjects were born in Canada (94%), their mean age at entry was 20 years, 68% were boys and almost half (44%) had injected drugs before recruitment. Among 778 never injectors at entry, 130 subjects initiated injection in 1898 person-years of follow-up (incidence rate: 6.8 per 100 person-years). When controlling for age, calendar year was not a significant predictor of incidence rate. Prevalence of current injection was stable (around 30%). Odds of both sharing behaviors decreased by approximately 10% per year.
Conclusions: In addition to injection paraphernalia sharing reduction efforts, interventions aimed at preventing initiation into injection drug use among high-risk youth are needed.