Results of a zero-inflated negative binomial regression analysis of the association between cumulative days supplied and average daily MED in the first 8 weeks after injury and days on benefits and benefit status after the 8-week exposure window up to 1 year after injury
| Predictor | Days on benefits after exposure window | On benefits after exposure window | ||
| IRR (95% CI) | OR (95% CI) | |||
| Unadjusted | Adjusted | Unadjusted | Adjusted | |
| Cumulative days’ supply in first 8 weeks | ||||
| Opioids (n=26 673) | ||||
| For every 7-day increase | 1.10 (1.09 to 1.11) | 1.10 (1.09 to 1.11)* | 1.32 (1.30 to 1.35) | 1.35 (1.33 to 1.39)* |
| NSAIDs (n=39 571) | ||||
| For every 7-day increase | 1.07 (1.06 to 1.08) | 1.04 (1.03 to 1.05)† | 1.37 (1.35 to 1.39) | 1.25 (1.23 to 1.28)† |
| SMRs (n=23 837) | ||||
| For every 7-day increase | 1.07 (1.05 to 1.08) | 1.03 (1.01 to 1.04)‡ | 1.41 (1.37 to 1.43) | 1.23 (1.20 to 1.27)‡ |
| Average daily MED in first 8 weeks (n=29 818) | ||||
| For every 30 mg/day increase | 1.06 (1.04 to 1.09) | 1.04 (1.02 to 1.07)§ | 1.02 (0.99 to 1.05) | 1.02 (0.99 to 1.04)§ |
*Adjusted for sex, age, year of injury, income, cumulative days of opioids in previous year.
†Adjusted for sex, age, year of injury, income, cumulative days of opioids within 8 weeks, diagnosis code, cumulative days of SMRs within 8 weeks, spine X-ray within first 8 weeks.
‡Adjusted for sex, age, year of injury, income, cumulative days of opioids within 8 weeks, cumulative days of NSAIDs within 8 weeks, spine X-ray within first 8 weeks.
§Adjusted for sex, age, year of injury, income, diagnosis code, spine X-ray within first 8 weeks, pain specialist visit within first 8 weeks, health authority, NSAID dispense within first 8 weeks, cumulative days of opioids in previous year, anticonvulsant dispense within first 8 weeks.
IRR, incidence rate ratio; MED, morphine-equivalent dose; NSAID, non-steroidal anti-inflammatory drug; SMR, skeletal muscle relaxant.