Age and Chronic Disease – Specific Associations Between Opioid Agonist Treatment and Opioid Overdose Death By Age and Chronic Disease Status: Cohort Study Using Linked Administrative Health Data in New South Wales, Australia, 2001-2018

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

Theme: Epidemiology & Public Health Research Year: 2022

Background: Opioid agonist treatment (OAT) protects against opioid overdose mortality. In many
countries, the OAT population is aging, with concomitant increases in chronic diseases that may
increase overdose risk. We tested whether OAT protects against overdose death for clients who are
older or have chronic diseases.
Methods: The sample included all people prescribed OAT, 2001-2018, with linkage of OAT, mortality,
and hospitalisation records. Age groups were <30 years, 30-39 years, 40-49 years, and ≥50 years.
Opioid overdose deaths and hospitalisations for chronic respiratory, circulatory, kidney, and liver
diseases were defined using ICD-10 codes. We developed generalised estimating equation models of
overdose mortality rates in and out of treatment, and compared buprenorphine and methadone, for
different age groups and in people with each category of disease.
Results: Among 45,664 OAT clients, there were 1,279 opioid overdose deaths. For all age groups,
being in OAT was associated with reduced risk of opioid overdose death relative to no OAT, with no
evidence of a difference between methadone and buprenorphine, including in older age groups
(adjusted RR buprenorphine relative to methadone ≥50 years: 0.59, 95% CI: 0.27, 1.30). Among
people with systemic diseases, being in OAT was safer than not being in OAT. During OAT, fatal
overdose was significantly lower during treatment with buprenorphine relative to methadone for
people with circulatory (adjusted RR: 0.47, 95% CI: 0.23, 0.97) and respiratory (adjusted RR: 0.32,
95% CI: 0.12, 0.84) diseases. For people with liver or kidney disease, there was no evidence of a
significant difference between buprenorphine and methadone in overdose mortality rates.
Conclusion: OAT produces significant reductions in opioid overdose mortality risk in older clients,
but comorbidities should be taken into account in determining the appropriate treatment.
Buprenorphine may be preferable to methadone for reducing opioid overdose mortality in clients
with respiratory or circulatory disease.
Disclosure of Interest Statement:
SL, SN, & LD have received untied educational grant funding from Indivior unrelated to this work. SN
& LD have received untied educational grant funding from Seqirus unrelated to this work.

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