Table 1 Baseline characteristics

Age, years (sd)

52.7 (13.7)

54.2 (13.8)

52.2 (13.7)

P = 0.068^a

Female (%)

454 (55.6)

129 (58.6)

325 (54.5)

P = 0.303^b

College-level education (%)^d

288 (35.3)

81 (36.8)

207 (34.7)

P = 0.621^b

Employed (%)¹

728 (89.4)

205 (93.2)

523 (88.1)

P = 0.039^b

Sick leave (%)

128 (15.7)

16 (7.3)

112 (18.8)

P < 0.001^b

Current smoker (%)

138 (16.9)

31 (14.1)

107 (18.0)

P = 0.208^b

History of low back surgery (%)

98 (12.0)

21 (9.6)

77 (12.9)

P = 0.225^b

Co-morbidity, self-reported (%)

145 (17.8)

22 (10.0)

123 (20.6)

P < 0.001^b

Health-related quality of life (0–1), [iqr]

0.66 [0.44; 0.78]

0.72 [0.65; 0.78]

0.66 [0.39; 0.72]

P < 0.001^c

Roland Morris Disability Questionnaire, 0–23 points, high score = high disability, (sd)

14.0 (4.9)

11.9 (4.9)

14.7 (4.7)

P < 0.001^a

Chronic pain (>  12 weeks = yes), (%)

739 (90.6)

196 (89.1)

543 (91.1)

P = 0.418^b

Numerical Pain Rating (0–10), (sd)

5.2 (2.4)

4.6 (2.2)

5.4 (2.5)

P < 0.001^a

STarT Back Tool, High risk, (%)¹

301 (37.0)

42 (19.2)

259 (43.5)

P < 0.001^b

‘I think that finding the cause of pain is important for my recovery’ (%)²

790 (96.9)

210 (95.9)

580 (97.3)

P = 0.358^b

‘I think x-rays and MR scans are important part for my recovery’ (%)²

717 (88.0)

182 (83.1)

535 (89.8)

P = 0.015^b

‘Have you been advised by your general practitioner to stay active despite your back pain?’, yes (%)³

475 (68.3)

132 (69.8)

343 (67.6)

P = 0.647^b

‘Have you been advised from a physiotherapist or chiropractor to stay active despite your back pain?’, yes (%)⁴

611 (79.5)

161 (79.7)

450 (79.4)

P = 1.000^b