Table 4.
Results from the cox proportional hazard model with a gamma frailty for the duration of continuous retention in opioid agonist treatment among 122,173 episodes from 37,785 clients who received opioid agonist treatment and completed induction in British Columbia, Canada, 2008–2018.
| Explanatory variable | Hazard ratio |
95% CI |
|---|---|---|
| Year of initiation | 0.99 | (0.99, 1.00) |
| Individual characteristics | ||
| Male | Reference | |
| Female | 1.07 | (1.05, 1.10) |
| Age | ||
| <40 | Reference | |
| ≥40 | 0.85 | (0.83, 0.87) |
| CDS | ||
| <4 | Reference | |
| ≥4 | 0.95 | (0.92, 0.97) |
| Living area | ||
| Urban | Reference | |
| Rural | 1.09 | (1.05, 1.12) |
| Ever indication of unstable housing | ||
| No | Reference | |
| Yes | 1.20 | (1.17, 1.24) |
| Incarceration status | ||
| Never | Reference | |
| Previously incarcerated, but currently in community | 1.24 | (1.22, 1.27 |
| Currently incarcerated | 1.15 | (1.10, 1.19) |
| Ever evidence of social assistance | ||
| No | Reference | |
| Yes | 0.89 | (0.87, 0.91) |
| Other comorbidities/diagnoses | ||
| Alcohol use disorder | 1.03 | (1.01, 1.05) |
| Other substance use disorder | 0.81 | (0.79, 0.84) |
| Human immunodeficiency virus | 0.94 | (0.89, 0.98) |
| Hepatitis C virus | 0.94 | (0.91, 0.98) |
| Mental health condition | 0.79 | (0.77, 0.81) |
| Chronic pain | 0.92 | (0.90, 0.94) |
| History of tobacco use | 0.96 | (0.94, 0.97) |
| Treatment characteristics | ||
| Medication at the end of induction for first year observed (2008) | ||
| Methadone | Reference | |
| Buprenorphine/naloxone | 2.50 | (2.35, 2.66) |
| Medication at the end of induction for mid-point year of follow-up (2013) | ||
| Methadone | Reference | |
| Buprenorphine/naloxone | 2.12 | (2.06, 2.18) |
| Medication at the end of induction for last year observed (2018) | ||
| Methadone | Reference | |
| Buprenorphine/naloxone | 1.79 | (1.74, 1.85) |
| Slow-release oral morphinea | 1.28 | (1.16, 1.43) |
| Maintenance dose at or above minimum effective dose | ||
| No | Reference | |
| Yes | 0.79 | (0.78, 0.8) |
| Episode number | ||
| 1 | Reference | |
| 2 | 1.15 | (1.12, 1.17) |
| 3–4 | 1.20 | (1.17, 1.23) |
| 5–6 | 1.23 | (1.20, 1.26) |
| ≥7 | 1.35 | (1.32, 1.39) |
| Primary prescriber characteristics | ||
| Years of OAT prescribing experience | ||
| <1 | Reference | |
| 1–5 | 1.01 | (0.98, 1.05) |
| 5–10 | 1.02 | (0.99, 1.06) |
| >10 | 1.02 | (0.99, 1.05) |
| OAT client load | ||
| Q1 | Reference | |
| Q2 | 0.97 | (0.95, 1.00) |
| Q3 | 1.01 | (0.99, 1.04) |
| Q4 | 1.08 | (1.06, 1.11) |
| CHC prescriber | ||
| No | Reference | |
| Yes | 1.32 | (1.28, 1.37) |
| Estimated frailty variance | 0.38 |
Abbreviations: CDS: Clark chronic disease score, OAT: opioid agonist treatment, CHC: community health center.
a
Slow-release oral morphine was introduced in 2017, and thus not included in estimates prior to 2017.