Acute/subacute drug-related hospital-treated somatic disease incidents: interaction effect between OMT status (before versus during OMT) and patient characteristics
| Patient characteristics | p Value for interaction | Adjusted IRR (95% CI) |
| During-treatment characteristics | ||
| Interruption of OMT | 0.001 | |
| Continuous treatment | 6.1 (3.6 to 10.6) | |
| Interrupted treatment | 1.7 (1.0 to 2.9) | |
| Drug-use during OMT (illicit opioids, cannabis, benzodiazepines, central stimulants) | 0.07 | |
| 25th Percentile, quartile without drug use | 6.5 (3.5 to 12.0) | |
| 75th Percentile, quartile with most drug use | 3.6 (2.4 to 5.3) | |
| Pre-treatment characteristics | ||
| Employment years | 0.02 | |
| <1 year | 2.6 (1.3 to 5.2) | |
| 1–5 years | 4.1 (1.8 to 9.2) | |
| >5 years | 5.5 (2.7 to 11.2) | |
| Opioid dependence before OMT, years | 0.01 | |
| 8 years (25th percentile) | 3.3 (2.0 to 5.5) | |
| 16 years (75th percentile) | 5.4 (3.1 to 9.4) | |
Adjusted incidence rate ratios (IRR) estimated by Poisson regression (generalised estimating equations) before versus during OMT, during OMT as reference (incidence rate=1). Only characteristics showing significant interaction with OMT status are shown. Crude IRR are shown in table 2. Interaction was also tested for gender, age at OMT start, lifetime number of overdoses, years of education and age at heroin debut without showing significant interaction (p>0.1).
Patient-years at risk: 1000 before, 813 during and 91 after OMT. Number of incidents: 605 before, 310 during and 106 after OMT.
IRR, incidence rate ratio; OMT, opioid maintenance treatment.