Statistical analyses
REGRESSION, SENSITIVITY
Proportion-in-work outcomes were analyzed using logistic regression and time-to-RTW outcomes using Cox-regression. Self-reported outcomes were analyzed using linear mixed-effects models. Throughout, we adhered to the intention-to-treat principle. Due to multiple testing, P-values <0.017 were considered statistically significant and those <0.05 borderline (the latter was a post-hoc decision). Subgroup analyses were performed according to selected baseline values and time. Sensitivity analyses were conducted by imputing all missing data in best/worst case scenarios, and regarding return to stable work outcomes with different thresholds for what minimal duration constituted “stable” RTW (1, 4, 8 or 12 weeks).