Are overdoses treated by ambulance services an opportunity for additional interventions? A prospective cohort study
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Original versionAddiction 2015 10.1111/add.13026
To assess whether people who inject drugs (PWID) and who are treated for overdose by ambulance services have a greater mortality risk compared with other PWID, and to compare mortality risk within potentially critical time-periods (1 week, 1 month, 3 months, 6 months, 1 year, 5 years) after an overdose attendance with the mortality risk within potentially non-critical time-periods (time before and/or after critical periods).A total of 172 PWID street-recruited in 1997 and followed-up until the end of 2004.Interview data linked to data from ambulance records, Norwegian Correctional Services, Opioid Substitution Treatment records and National Cause of Death Registry. Separate Cox regression models (one for each critical time-period) were estimated.Ambulance services treated 54% of the participants for an overdose during follow-up. The mortality rate was 2.8 per 100 person-years for those with an overdose and 3.3 for those without; the adjusted hazard ratio (HR) was 1.3 (95% CI = 0.6, 2.6, P = 0.482). Mortality risk was greater in all but the shortest critical time-period following ambulance attendance than in the non-critical periods. The mortality risk remained significantly elevated during critical periods, even when adjusted for total time spent in prison and substitution treatment. The HR ranged from 9.4 (95% CI = 3.5, 25.4) in the month after an overdose to 13.9 (95% CI = 6.4, 30.2) in the 5-year period.Mortality risk among people who inject drugs is significantly greater in time-periods after an overdose attendance than outside these time-periods.