Factor | β | SE | p value | HRR | 95% CI | Time varying† |
---|---|---|---|---|---|---|
Variable selection was based on backward elimination, addition of suggested interactions, and validation in the testing sample. The results in the table were fit using the learning sample. | ||||||
*For continuous measures, the HRR is shown for a difference equal to the interquartile range of that particular measure: for the Roland Morris, a difference of 30; for the modified ASES, a difference of 37; for the WOMAC, a difference of 29; and for change in pain, a difference of 20. | ||||||
†For time varying effects, a piecewise proportional hazards model was used. In all cases in the model above, the coefficient is non-zero as given in the table up to 56 days post-origin and zero for the remainder of the time scale. | ||||||
‡Respondents were asked whether their workplace had made any offers of special arrangements to help them return to work. | ||||||
Functional status (4 wk) | ||||||
Roland Morris | 0.023 | 0.003 | ⩽0.0001 | 2.02* | (1.68 to 2.45) | Yes |
Mod ASES | 0.022 | 0.004 | ⩽0.0001 | 2.28* | (1.75 to 2.97) | Yes |
WOMAC | 0.032 | 0.006 | ⩽0.0001 | 2.52* | (1.78 to 3.56) | No |
Part of body | ||||||
(Back) | 0.0 | – | – | 1.0 | – | |
Upper limb | −0.466 | 0.180 | 0.0096 | 0.63 | (0.44 to 0.89) | No |
Lower limb | −0.956 | 0.345 | 0.0056 | 0.39 | (0.20 to 0.76) | No |
Change in pain grade | 0.012 | 0.003 | 0.0005 | 1.27* | (1.11 to 1.44) | Yes |
Workplace offers‡ | 0.645 | 0.124 | ⩽0.0001 | 1.91 | (1.49 to 2.43) | No |
Change in pain grade × workplace offers‡ | −0.018 | 0.005 | 0.0004 | 0.70* | (0.58 to 0.85) | Yes |
Poor recovery expectations | −0.432 | 0.112 | ⩽0.0001 | 0.65 | (0.52 to 0.81) | No |