A priori approach: multivariable model results for predicting injury as a function of shift length and other characteristics
| Relative risk (95% CI) | p Value | |
|---|---|---|
| Shift length (category) | ||
| ≤8 h | 0.70 (0.51 to 0.96) | 0.029 |
| >8 and ≤12 h | Referent | – |
| >12 and ≤16 h | 1.27 (0.91 to 1.77) | 0.158 |
| >16 and ≤24 h | 1.60 (1.22 to 2.10) | 0.001 |
| >24 h | 1.18 (0.16 to 8.49) | 0.87 |
| Overnight shift | 0.78 (0.65 to 0.93) | 0.005 |
| Consecutive shift | 0.84 (0.62 to 1.15) | 0.29 |
| Crew familiarity | ||
| 0–1 shifts | Referent | – |
| 2–7 shifts | 1.05 (0.88 to 1.24) | 0.59 |
| 8–19 shifts | 1.08 (0.90 to 1.30) | 0.39 |
| ≥20 shifts | 1.14 (0.91 to 1.41) | 0.25 |
| Hours of recovery | 1.00 (1.00 to 1.00) | 0.85 |
| Employment status | ||
| Full-time | Referent | – |
| Part-time | 0.91 (0.78 to 1.07) | 0.26 |
| Midpoint agency size (20 person units) | 0.99 (0.86 to 1.13) | 0.88 |
*Model includes 961 827 observations. The hours of recovery was not available for the first shift in the data set.