Risk-factors for methadone-specific deaths in Scotland's methadone-prescription clients between 2009 and 2013.
To quantify gender, age-group and quantity of methadone prescribed as risk factors for drugs-related deaths (DRDs), and for methadone-specific DRDs, in Scotland's methadone-prescription clients.



Linkage to death-records for Scotland's methadone-clients with one or more Community Health Index (CHI)-identified methadone prescriptions during July 2009 to June 2013.



Scotland's Prescribing Information System and National Records of Scotland.



Covariates defined at first CHI-identified methadone prescription, and person-years at-risk (pys) thereafter until the earlier of death-date or 31 December 2013. Methadone-specific DRDs were defined as: methadone implicated but neither heroin nor buprenorphine. Hazard ratios (HRs) were assessed using proportional hazards regression.



Scotland's CHI-identified methadone-prescription cohort comprised 33,128 clients, 121,254 pys, 1,171 non-DRDs and 760 DRDs (6.3 per 1,000 pys), of which 362 were methadone-specific. Irrespective of gender, methadone-specific DRD-rate, per 1,000 pys, was higher in the 35+ age-group (4.2; 95% CI: 3.6-4.7) than for younger clients (1.9; 95% CI: 1.5-2.2). For methadone-specific DRDs, age-related HRs (e.g., 2.9 at 45+ years; 95% CI: 2.1-3.9) were steeper than for all DRDs (1.9; 95% CI: 1.5-2.4); there was no hazard-reduction for females; no gender by age-group interaction; and, unlike for all DRDs, the highest quintile for quantity of prescribed methadone at cohort-entry (>1960mg) was associated with increased HR (1.8; 95% CI: 1.3-2.5).



Higher methadone-specific DRD rates in older clients, irrespective of gender, call for better understanding of methadone's pharmaco-dynamics in older, opioid-dependent clients, many with progressive physical or mental ill-health.
MRC Biostatistics Unit, Cambridge CB2 0SR, United Kingdom.
Lu
L
Gao
MRC Biostatistics Unit, Cambridge CB2 0SR, United Kingdom.
Polyxeni
P
Dimitropoulou
Usher Institute of Population Health Sciences and Informatics, Edinburgh University, EDINBURGH EH16 4UX, United Kingdom.
J Roy
JR
Robertson
Information Services Division, NHS National Services Scotland, Edinburgh EH12 9EB, United Kingdom.
Stuart
S
McTaggart
Information Services Division, NHS National Services Scotland, Edinburgh EH12 9EB, United Kingdom; Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, United Kingdom.
Marion
M
Bennie
MRC Biostatistics Unit, Cambridge CB2 0SR, United Kingdom; Department of Mathematics and Statistics, Strathclyde University, Glasgow G1 1XH, United Kingdom. Electronic address: sheila.bird@mrc-bsu.cam.ac.uk.
Sheila M
SM
Bird
D000328:Adult; D000367:Age Factors; D000701:Analgesics, Opioid / Q000506:poisoning* / Q000627:therapeutic use; D002423:Cause of Death; D005260:Female; D006556:Heroin Dependence / Q000534:rehabilitation*; D006801:Humans; D008297:Male; D008691:Methadone / Q000506:poisoning* / Q000627:therapeutic use; D008875:Middle Aged; D058850:Opiate Substitution Treatment; D012307:Risk Factors; D012606:Scotland; D013405:Suicide; D055815:Young Adult
D000701:Analgesics, Opioid; D008691:Methadone
Age-group; Daily-dose; Deaths; Drugs-related; Gender; Methadone-specific; Prescribed-methadone; Quantity; Quintiles; Risk-factors