Table 1 Characteristics of the full sample and stratified by class

Sociodemographics

Age (y), mean (SD)

66.0 (13.0)

66.0 (7.7)

72.3 (9.6)

62.8 (8.4)

66.6 (8.3)

Women, n (%)

231 (53.1)

84 (49.7)

22 (71.0)

23 (69.7)

102 (50.5)

Educational level, n (%)

 Low

244 (56.5)

87 (51.5)

14 (45.2)

22 (68.8)

121 (60.5)

 High

188 (43.5)

82 (48.5)

17 (54.8)

10 (31.3)

79 (39.5)

Employed, n (%)

201 (46.2)

87 (51.5)

7 (22.6)

10 (30.3)

97 (48.0)

Comorbidities, > 4, N (%)

34 (10.2)

6 (3.6)

24 (77.4)

3 (10.3)

1(0.6)

Intake of medications for back pain, n (%)

165 (39.9)

28 (17.6)

20 (64.5)

23 (74.2)

94 (48.7)

Pain characteristics

Pain intensity, mean (SD)

5.3 (2.30)

3.9 (2.3)

6.9 (2.1)

6.1 (1.7)

6.1 (2.0)

Duration of current back pain episode, n (%)

 0–14 days

150 (39.9)

68 (47.2)

9 (37.5)

13 (44.8)

60 (33.5)

 25-90 days

151 (40.2)

54 (37.5)

4 (16.7)

8 (27.6)

85 (47.5)

 91-365

46 (12.2)

15 (10.4)

7 (29.2)

4 (13.8)

20 (11.2)

 ≥366 days

29 (7.7)

7 (4.9)

4 (16.7)

4 (13.8)

14 (7.8)

Widespread Pain, n (%)

30 (6.9)

7 (4.1)

4 (12.9)

6 (18.2)

13 (6.4)

Disability

RMDQ score, median (IQR)

9.0 (4–13)

4.0 (2–6)

14.5 (12–17)

16.0 (12–19)

12.0 (8–14)

Psychological factors and pain related behavior

FABQ score, median (IQR)

9.0 (5–13)

5.0 (0.5-9)

17.0 (14–20)

14.0 (10-17.5)

11.0 (7–14)

CES-D score, median (IQR)

8.0 (3–13)

4.0 (1-7.3)

13.0 (10–18)

26.0 (20–30)

9.0 (5–13)

Back pain related beliefs and attitudes

PCS score, median (IQR)

9.0 (4–15)

4.0 (1-6.5)

14.0 (10–19)

29.0 (23-37.5)

12.0 (7–16)

BBQ score, mean (SD)

23.8 (7.1)

19.7 (5.4)

29.5 (6.8)

33.1 (7.2)

25.3(5.9)

Expectations, n (%)

Fully recovered or much better

328 (75.7)

122 (72.2)

21 (70.0)

23 (69.7)

162 (80.6)

No change or worse

105 (24.3)

47 (27.8)

9 (30.0)

10 (30.3)

39 (19.4)