Table 3

Mediation analyses of the impact of male sex on spinal radiographic progression

VariableOR95% CIP value
Effect of male sex on BL mSASSS at start of each X-ray interval1.831.28 to 2.61<0.001
Effect of BL mSASSS on spinal radiographic progression1.071.05 to 1.09<0.001
Total effect of male sex on spinal radiographic progression3.411.87 to 6.21<0.001
Direct effect of male sex on spinal radiographic progression2.061.15 to 3.670.01
Indirect effect of male sex on spinal progression (via BL mSASSS)1.041.01 to 1.07<0.001
  • Results from different models with spinal radiographic progression defined as an increase of ≥2 mSASSS units in 2 years. The total effect of male sex on spinal progression is estimated after adjustment for prior treatment with tumour necrosis factor inhibitors and the length of the radiographic interval. The direct effect is estimated with addition of the baseline mSASSS at start of each X-ray interval to the latter model.

  • BL, baseline; mSASSS, modified Stoke Ankylosing Spondylitis Spinal Score.