Stratification Variables
LBP, NRS, pain
Subgroups were defined according to baseline reporting of the duration of the current LBP episode (≤12 weeks vs >12 weeks) and the average LBP intensity in the preceding week (≤5 vs >5 NRS points). The duration of LBP was assessed by the question “What is the length of time you have had LBP during this episode?” with four response options “less than 1 week,” “1-4 weeks,” “5-12 weeks,” and “more than 12 weeks,” whereas the average LBP intensity was measured by the NRS (range 0, “no pain,” to 10, “worst pain imaginable”).