Table 3:
Adjusted opioid overdose mortality incident rate ratios during time prescribed methadone or buprenorphine, relative to time out of OAT, and during time prescribed buprenorphine relative to time prescribed methadone, by age group
| Treatment | PY | N opioid overdose deaths | Crude mortality rate per 1,000 PY (95% CI) | GEE Adjusted IRR (95% CI) |
MSM Adjusted IRR (95% CI) |
|||
|---|---|---|---|---|---|---|---|---|
| Age group | Comparison of each treatment to time out of OAT | Comparison of buprenorphine to methadone | Comparison of each treatment to time out of OAT | Comparison of buprenorphine to methadone | ||||
| Out of OAT | 30,027 | 123 | 4.1 (3.4–4.9) | Ref. | Ref. | |||
| <30 years | Buprenorphine | 11,016 | 9 | 0.8 (0.4–1.6) | 0.20 (0.09–0.45) | 0.58 (0.24–1.38) | 0.18 (0.07–0.45) | 0.46 (0.17–1.26) |
| Methadone | 25,533 | 37 | 1.4 (1.0–2.0) | 0.34 (0.22–0.53) | Ref. | 0.39 (0.24–0.63) | Ref. | |
| Out of OAT | 45,140 | 321 | 7.1 (6.4–7.9) | Ref. | Ref. | |||
| 30–39 years | Buprenorphine | 18,229 | 23 | 1.3 (0.8–1.9) | 0.18 (0.11–0.29) | 0.80 (0.46–1.40) | 0.17 (0.10–0.31) | 0.61 (0.32–1.18) |
| Methadone | 47,208 | 77 | 1.6 (1.3–2.0) | 0.22 (0.16–0.30) | Ref. | 0.28 (0.20–0.39) | Ref. | |
| Out of OAT | 27,428 | 210 | 7.7 (6.7–8.8) | Ref. | Ref. | |||
| 40–49 years | Buprenorphine | 12,901 | 17 | 1.3 (0.8–2.1) | 0.17 (0.09–0.31) | 0.61 (0.32–1.17) | 0.20 (0.09–0.44) | 0.70 (0.30–1.64) |
| Methadone | 32,794 | 73 | 2.2 (1.8–2.8) | 0.28 (0.20–0.39) | Ref. | 0.28 (0.19–0.40) | Ref. | |
| Out of OAT | 10,800 | 102 | 9.4 (7.8–11.5) | Ref. | Ref. | |||
| 50+ years | Buprenorphine | 6,195 | 11 | 1.8 (1.0–3.2) | 0.18 (0.08–0.39) | 0.47 (0.21–1.02) | 0.22 (0.08–0.61) | 0.49 (0.17–1.41) |
| Methadone | 14,785 | 56 | 3.8 (2.9–4.9) | 0.39 (0.26–0.58) | Ref. | 0.45 (0.29–0.69) | Ref. | |
OAT = opioid agonist treatment. PY = person-years. GEE = generalized estimating equation. IRR = incident rate ratio. MSM = marginal structural model. Ref = reference category for IRR. GEE models are adjusted for year, sex, geographical remoteness, indigeneity, socio-economic disadvantage index, recent: incarceration, mental health ambulatory outpatient activity, previous OAT history, hospital admissions for mood and psychosis disorders, substance use and self-harm. MSM models are weight adjusted for treatment selection bias using: year^, sex, geographical remoteness, Indigenous status, socio-economic disadvantage index, recency of: criminal charges^, previous OAT history, most recent OAT^, hospital admissions for respiratory^, substance use^, previous NFOD on OAT, prescriber preference^ and censorship using: year^, sex, geographical remoteness, indigeneity, socio-economic disadvantage index, previous OAT history, treatment^ and treatment by year interaction^ and recency of: incarceration^, hospital admissions for mood^ and psychosis disorders^, substance use^ and mental health ambulatory outpatient activity^. ^=fitted at baseline and time varying.