Table 2 Baseline variables and logistic regression analyses of univariables

Clinical variables

Sex: female/all (% female), reference female

Age^w: mean (SD, range), reference 18 years

Body Mass Index (BMI): mean (SD, range), ref. 18 kg/m²

N^o with radiculopathy/all, n (%), ref. non-specific

Low back pain classification, n (%) overall p

 Non-specific LBP without radiation below the knee

 Non-specific LBP with pain below the knee^w

 Radiculopathy^w

Intensity of back pain^2p, mean (SD, range), ref. 0

Intensity of leg pain², mean (SD, range), ref. 0

Pain score^2p (back + leg pain), mean (SD, range), ref. 3

Duration of actual pain^p: ref. ≤ 3 months (%)

Use of pain medication: (%5-7 days/week), ref. less often

Disability (Roland Morris)^w: median (range), ref. 3

N^o ‘much bothered by widespread pain^p the preceding two weeks’/all, n

(%), reference: ‘not much bothered’

Forward-flexion (Mod. Schober): mean (SD, range), ref. 0.5 cm

Side-flexion^p: mean (SD, range), reference 4 cm

Tender points^p: median (range), reference 0

Disc Degenerat. Score L1-4: 0-12, median (range), ref. 0

Disc herniation^p L4-5 without radiculopathy, ref. none

Disc herniation^p L5-S1 without radiculopathy, ref. none

Psychosocial and life style variables

Fear avoidance^w: (0-30), dichotomised, reference <28

Waddell’s signs^w: n/all (% with one or more), ref. none

Bodily distress^w: 0-11, median (range), ref. 0

Worrying and health anxiety^w: 0-7, median (range), ref. 0

Mental distress^w: 0-8, median (range), ref. 0

Depressive symptom^w: 0-6, median (range), ref. 0

General health perceived as bad^w/all, reference: splendid, very good, good

or not so good

N^o ‘blaming work for low back pain^p’/ all, n (%), ref. ‘not blaming work

or only partly blaming work’

N^o ‘not convinced about return to work within 6 months^w’/all, n (%), ref.

‘convinced about return to work’

N^o with compensation claim^w/all, n (%), ref. no claim

School education^p, n (%) overall p

 < 10 years

 10 years

 high school or alike

 something else

Vocational education, n (%) overall p

 none

 unskilled, one or more courses

 skilled education, craftsman, clerk

 short and intermediate education < 4 years

 long education > 4 years

Marital status overall p

married

 living together, not married

 alone, not previously living together

 alone (previous married or living together)

 something else

N^o with no children/all, n (%), ref. having children

N^o with no home ownership/all, n (%), ref. home ownership

Job^w overall p

 unskilled

 skilled

 salaried employee

 independent

 something else

Job: N^o leader/all, n (%), ref. not leader

Personal income^p €, n (%) overall p

 <20,137

 20,137-33,561

 33,562-50,341

 >50,341

Income of family €, n (%) overall p

 < 33,562

 33,562-50,341

 50,342-67,123

 > 67,123

Smoking^p, n (%) overall p

 never smoking

 previously smoking

 smoking currently

N^o drinking alcohol less than once per month^p/all, n (%), ref. drinking

regularly, at least once/month

Exercise in leisure time^p, dichotomised

Vigorous or regular exercise several times a week including heavy

gardening or housework, n (%)

Walking, cycling or light exercise some hours a week or no exercise at

all, n (%)