Does opioid agonist treatment reduce overdose mortality risk in people who are older or have physical comorbidities? Cohort study using linked administrative health data in New South Wales, Australia, 2002–17

• Published in: Addiction (Abingdon, England) England), 2023-08, Vol.118 (8), p.1527-1539
• Main Authors: Larney, Sarah, Jones, Nicola R., Hickman, Matthew, Nielsen, Suzanne, Ali, Robert, Degenhardt, Louisa
• Format: Article
• Language: English
• Subjects: Age; Age differences; Age groups; Aged; Agonists; Analgesics, Opioid - therapeutic use; Australia; Buprenorphine; Buprenorphine - therapeutic use; Chronic illnesses; Chronic respiratory diseases; Cohort analysis; Cohort Studies; Comorbidity; Death; Death & dying; Disease; Drug abuse; Drug addiction; Drug overdose; Drug Overdose - drug therapy; Health information; Hospitalization; Humans; Imprisonment; Kidney diseases; Liver; Liver diseases; Mental health care; Mental health services; Methadone; Methadone - therapeutic use; Middle Aged; Mortality; multi‐morbidity; Narcotics; New South Wales - epidemiology; older adults; Older people; Opiate Overdose - drug therapy; Opiate Substitution Treatment; opioid agonist treatment; Opioid-Related Disorders - epidemiology; Opioids; Overdose; Pharmacists; Protection; Respiratory diseases; Retrospective Studies; Risk; Risk reduction; Structural models; Substance use disorder; Time out
• ISSN: 0965-2140; 1360-0443; 1360-0443
• DOI: 10.1111/add.16178

Aims To quantify the association between opioid agonist treatment (OAT) and overdose death by age group; test the hypothesis that across different age groups, opioid overdose mortality is lowest during OAT with buprenorphine compared with time out of treatment or OAT with methadone; and test associations between OAT and opioid overdose mortality in the presence of chronic circulatory, respiratory, liver and kidney diseases. Design Retrospective observational cohort study using linked administrative data. Setting New South Wales, Australia. Participants A total of 37 764 people prescribed OAT, 1 August 2002 and 31 December 2017. Measurements OAT exposure, opioid overdose mortality and key confounders were measured using linked population data sets on OAT entry and exit, hospitalization, mental health care, incarceration and mortality. ICD‐10 codes were used to define opioid overdose mortality and chronic disease groups of interest. Findings Relative to time out of treatment, time in OAT was associated with a lower risk of opioid overdose death across all age groups and chronic diseases. Among people aged 50 years and older, there was weak evidence that buprenorphine may be associated with greater protection against opioid overdose death than methadone [generalized estimating equation (GEE) adjusted incident rate ratio (aIRR) = 0.47; 95% confidence interval (CI) = 0.21, 1.02; marginal structural models (MSM) aIRR = 0.49; 95% CI = 0.17, 1.41]. Buprenorphine was associated with greater protection against overdose death than methadone for clients with circulatory (MSM aIRR = 0.27; 95% CI = 0.11, 0.67) or respiratory (MSM aIRR = 0.26; 95% CI = 0.07, 0.94) diseases, but not liver (MSM aIRR = 0.59; 95% CI = 0.14, 2.43) or kidney (MSM aIRR = 1.16; 95% CI = 0.31, 4.36) diseases. Conclusions Opioid agonist treatment (OAT) appears to reduce mortality risk in people with opioid use disorder who are older or who have physical comorbidities. Opioid overdose mortality during OAT with buprenorphine appears to be lower and reduced in clients with circulatory and respiratory diseases compared with OAT with methadone.