Modelling crack cocaine use trends over 10 years in a Canadian setting

Crack cocaine use among illicit drug users is associated with a range of health and community harms. However, long-term epidemiological data documenting patterns and risk factors for crack use initiation remain limited especially among injection drug users. We investigated longitudinal patterns of crack cocaine use among polydrug users in Vancouver, Canada.We examined the rate of crack use among injection drug users enrolled in a prospective cohort study in Vancouver, Canada between 1996 and 2005. We also used a Cox proportional hazards regression analysis to identify independent predictors of crack use initiation among this population.In total, 1603 injection drug users were recruited between May 1996 and December 2005. At baseline, 7.4% of participants reported ever using crack and this rate increased to 42.6% by the end of the study period (Mantel trend test P0.001). Independent predictors of crack use initiation during the study period included frequent cocaine injection, crystal methamphetamine injection, residency in the city's drug using epicenter and involvement in the sex trade (all P0.05).These findings demonstrate a massive increase in crack use among injection drug users in a Canadian setting. Our findings also highlight the complex interactions that contribute to the initiation of crack use among injection drug users and suggest that evidence-based interventions are urgently needed to address crack use initiation and to address harms associated with its ongoing use.