Mixed negative-binomial model of number of opioid prescriptions 3 months, 12 months and 24 months after hip or knee arthroplasty including a hospital-level random effect (n=14 010)†. The ethnicity reference group is a composite of all ethnicities other than European NZ
| 3 months post surgery | 12 months post surgery | 24 months post surgery | ||||
| HR | 95% CI | HR | 95% CI | HR | 95% CI | |
| Opioid scripts 12 months presurgery | 1.083*** | 1.079 to 1.087 | 1.136*** | 1.130 to 1.141 | 1.147*** | 1.141 to 1.154 |
| Female | 1.124*** | 1.072 to 1.177 | 1.177*** | 1.121 to 1.237 | 1.195*** | 1.134 to 1.259 |
| Ethnicity: European NZ | 1.247*** | 1.171 to 1.329 | 1.121*** | 1.051 to 1.196 | 1.01 | 0.944 to 1.080 |
| Age | 0.994*** | 0.992 to 0.996 | 0.998 | 0.996 to 1.001 | 0.998* | 0.995 to 1.000 |
| Mean postsurgical NDVI (standardised) | 0.969*** | 0.947 to 0.992 | 0.971** | 0.947 to 0.995 | 0.969** | 0.944 to 0.994 |
| Knee | 1.653*** | 1.578 to 1.731 | 1.594*** | 1.519 to 1.673 | 1.547*** | 1.471 to 1.627 |
| COPD | 1.219*** | 1.133 to 1.311 | 1.272*** | 1.175 to 1.378 | 1.374*** | 1.262 to 1.496 |
| CHD | 1.133*** | 1.057 to 1.214 | 1.091** | 1.012 to 1.175 | 1.069* | 0.988 to 1.157 |
| Traumatic brain Injury | 1.197* | 0.992 to 1.444 | 1.335*** | 1.088 to 1.637 | 1.448*** | 1.166 to 1.799 |
| Days in hospital | 1.015*** | 1.009 to 1.022 | 1.035*** | 1.027 to 1.043 | 1.037*** | 1.029 to 1.045 |
| Variance of hospital random effect | 1.164*** | 1.064 to 1.272 | 1.072*** | 1.020 to 1.127 | 1.071** | 1.009 to 1.137 |
***p<0.01, **p<0.05, *p<0.1.
†Following IDI protocols, all sample sizes have been rounded to the nearest multiple of three.
CHD, coronary heart disease; COPD, chronic obstructive pulmonary disease; IDI, Integrated Data Infrastructure; NDVI, Normalised Difference Vegetation Index; NZ, New Zealand.