Table 3 Multivariable linear regression analyses exploring factors associated with BASFI QN8 and BASFI QN7

BASFI QN8; the ability to look over shoulder

 R²

0.41

0.47

0.29

 Constant

 − 0.70 (− 1.97 to 057)

0.31

 − 0.31 (− 1.66 to 1.05)

0.70

 − 1.08 (− 3.22 to 1.06)

0.32

 Age, years

0.06 (0.04 to 0.08)

 < 0.001

0.05 (0.03 to 0.08)

 < 0.001

0.07 (0.03 to 0.10)

 < 0.001

 ASDAS CRP, score

0.98 (0.70 to 1.25)

 < 0.001

0.94 (0.61 to 1.27)

 < 0.001

1.07 (0.57 to 1.56)

 < 0.001

 mSASSS, score

0.06 (0.05 to 0.08)

 < 0.001

0.06 (0.05 to 0.08)

 < 0.001

0.06 (0.03 to 0.09)

 < 0.001

 Female sex

0.10 (− 0.42 to 0.62)

0.70

NA

NA

BASFI QN7; the ability to climb stairs without a handrail

 R²

0.37

0.36

0.35

 Constant

 − 1.53 (− 2.45 to − 0.60)

0.001

 − 1.10 (− 2.09 to − 1.00)

0.032

 − 0.76 (− 2.30 to 0.78)

0.33

 Age, years

0.03 (0.01 to 0.04)

 < 0.001

0.03 (0.01 to 0.04)

 < 0.001

0.02 (− 0.00 to 0.04)

0.07

 ASDAS CRP, score

0.36 (0.17 to 0.54)

 < 0.001

0.37 (0.15 to 0.59)

0.001

0.35 (0.03 to 0.67)

0.034

 BMI, kg/m²

0.03 (0.01 to 0.06)

0.022

0.03 (0.00 to 0.06)

0.040

0.02 (− 0.03 to 0.07)

0.33

 Fatigue, score

0.10 (0.04 to 0.16)

0.001

0.11 (0.03 to 0.18)

0.006

0.09 (− 0.01 to 0.18)

0.08

 Tenderness, score

0.08 (0.02 to 0.14)

0.007

0.06 (− 0.02 to 0.13)

0.17

0.11 (0.01 to 0.20)

0.026

 BASMI, score

0.09 (− 0.00 to 0.19)

0.059

0.05 (− 0.06 to 0.16)

0.36

0.22 (0.02 to 0.42)

0.033

 Female sex

0.40 (0.13 to 0.67)

0.003

NA

NA