title: Modelling crack cocaine use trends over 10 years in a Canadian setting.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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 P < 0.001). 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 P < 0.05).
  
  
  CONCLUSIONS
  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.
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada.
authors.forename: Dan
authors.initials: D
authors.lastname: Werb
authors.forename: Kora
authors.initials: K
authors.lastname: Debeck
authors.forename: Thomas
authors.initials: T
authors.lastname: Kerr
authors.forename: Kathy
authors.initials: K
authors.lastname: Li
authors.forename: Julio
authors.initials: J
authors.lastname: Montaner
authors.forename: Evan
authors.initials: E
authors.lastname: Wood
mesh_terms: D002170:Canada; D019970:Cocaine-Related Disorders / Q000150:complications / Q000453:epidemiology*; D016578:Crack Cocaine / Q000009:adverse effects*; D005260:Female; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D015819:Substance Abuse, Intravenous / Q000150:complications / Q000453:epidemiology
chemical_list: D016578:Crack Cocaine; D013287:Illicit Drugs