title: Non-fatal overdose as a risk factor for subsequent fatal overdose among people who inject drugs.
abstract: OBJECTIVE
  To examine the relationship between non-fatal overdose and risk of subsequent fatal overdose.
  
  
  METHODS
  We assessed risk factors for overdose death among two prospective cohorts of persons who inject drugs (PWID) in Vancouver, Canada. Extended Cox regression was used to examine if reports of non-fatal overdose were associated with the time to fatal overdose while adjusting for other behavioral, social and structural confounders.
  
  
  RESULTS
  Between May, 1996 and December, 2011, 2317 individuals were followed for a median of 60.8 months. In total, 134 fatal overdose deaths were identified for an incidence density of 8.94 (95% confidence interval [CI]: 7.55-10.59) deaths per 1000 person-years. During the study period there were 1795 reports of non-fatal overdose. In a multivariate model, recent non-fatal overdose was independently associated with the time to overdose mortality (adjusted hazard ratio [AHR]=1.95; 95% CI: 1.17-3.27). As well, there was a dose response effect of increasing cumulative reports of non-fatal overdose on subsequent fatal overdose.
  
  
  CONCLUSIONS
  Reports of recent non-fatal overdose were independently associated with subsequent overdose mortality in a dose-response relationship. These findings suggest that individuals reporting recent non-fatal overdose should be engaged with intensive overdose prevention interventions.
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Caudarella
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada.
authors.forename: Huiru
authors.initials: H
authors.lastname: Dong
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada; Department of Medicine, University of British Columbia, Vancouver, Canada.
authors.forename: M J
authors.initials: MJ
authors.lastname: Milloy
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada; Department of Medicine, University of British Columbia, Vancouver, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kerr
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada; Department of Medicine, University of British Columbia, Vancouver, Canada. Electronic address: uhri-ew@cfenet.ubc.ca.
authors.forename: Evan
authors.initials: E
authors.lastname: Wood
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, Canada; Department of Medicine, University of British Columbia, Vancouver, Canada.
authors.forename: Kanna
authors.initials: K
authors.lastname: Hayashi
mesh_terms: D000328:Adult; D000368:Aged; D002170:Canada / Q000453:epidemiology; D062787:Drug Overdose / Q000453:epidemiology* / Q000401:mortality*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D015819:Substance Abuse, Intravenous / Q000453:epidemiology* / Q000401:mortality*
keywords: Injection drug use; Mortality; Non-fatal overdose; Vancouver