The Impact of Opioid Agonist Treatment on Fatal and Non-Fatal Drug Overdose Among People With a History of Opioid Dependence in NSW, Australia, 2001-2018: Findings From The Oats Retrospective Linkage Study

Author: Nicola Jones Matthew Hickman Sarah Larney Suzanne Nielsen Robert Ali Timothy Dobbins Louisa Degenhardt

Theme: Epidemiology & Public Health Research Year: 2022

Background: There are critical periods of mortality risk at onset and cessation of opioid agonist
treatment. We aim to determine whether non-fatal overdose followed the same pattern as fatal
overdose, comparing the first 4 weeks of treatment and treatment cessation and the remainder time
off treatment, with the remainder treatment time, to determine intervention markers.
Methods: Retrospective cohort study of people with a history of opioid agonist treatment using
linked New South Wales data. The incidence of non-fatal overdose hospitalization; emergency
department presentation; and fatal overdose from national death records were compared. Rates
were calculated using generalized estimating equations adjusting for demographics, year, and recent
health and incarceration events.
Results: The rate of an emergency department drug overdose presentation was highest. It was more
than three-fold the rate of opioid non-fatal overdose hospitalisation and 14 times higher than fatal
opioid overdose. It was also twice the rate of non-opioid non-fatal overdose hospitalisation. Fatal
overdose was lowest while in treatment. This differed from the measures of non-fatal overdose, the
overdose rate was elevated in the first four weeks in treatment as well as the first four weeks post

Conclusion: Retention on opioid agonist treatment is protective against drug related overdose.
There is elevated risk of non-fatal overdose at treatment initiation that is not evident for fatal
overdose, however the first month of treatment cessation is a critical period for both non-fatal and
fatal overdose. These findings emphasize the importance of treatment retention and interventions
for polysubstance overdose at cessation.
Disclosure of Interest Statement: Past three years, SL has received untied educational grant funding from Indivior; LD has received untied educational grant funding from Indivior and Seqirus. SN has received untied educational grants from Indivior and Seqirus. These untied grants are all unrelated to the current study. All other authors declare no competing interests.

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