Table 4.

Effects of disease activity on radiographic progression in subgroups—sensitivity analysis*

	Subgroup	Overall group		Men	Women
		p Value for the interaction	2-year increase in mSASSS per one-ASDAS unit increase (units, (95% CI))	2-year increase in mSASSS per one-ASDAS unit increase (units, (95% CI))	2-year increase in mSASSS per one-ASDAS unit increase (units, (95% CI))
Smoking	Smokers (n=35)	<0.001	2.13 (1.01 to 3.26)	2.56 (1.19 to 3.94)	–†
	Non-smokers (n=50)		0.34 (−0.03 to 0.70)	0.45 (−0.03 to 0.93)	0.06 (−0.22 to 0.34)
Occupation	‘Blue collar’ (n=40)	0.031	1.33 (0.66 to 2.00)	1.54 (0.78 to 2.29)	0.06 (−0.16 to 0.28)
	‘White collar’ (n=45)		0.20 (−0.36 to 0.77)	0.25 (−0.58 to 1.08)	−0.01 (−0.39 to 0.37)
Education	‘Non-university’ (n=78)	0.678	0.93 (0.47 to 1.39)	1.13 (0.56 to 1.71)	0.06 (−0.22 to 0.33)
	‘University’ (n=7)		−0.19 (−0.57 to 0.18)	−0.34 (−0.97 to 0.29)	0.00 (0.00 to 0.00)
Monthly gross personal income	<€1588 (n=51)	0.066	1.13 (0.51 to 1.75)	1.37 (0.58 to 2.16)	–†
	≥€1588 (n=34)		0.21 (−0.19 to 0.61)	0.26 (−0.21 to 0.72)	−0.09 (−0.99 to 0.81)
Monthly gross family income	<€3176 (n=43)	0.497	0.47 (0.01 to 0.92)	0.60 (0.06 to 1.13)	0.13 (−0.15 to 0.41)
	≥€3176 (n=13)		−0.05 (−0.45 to 0.35)	0.03 (−0.25 to 0.30)	−0.18 (−1.08 to 0.72)

*All models are time-lagged (2 years of time lag) and autoregressive (ie, adjusted for mSASSS in the 2-years before). Progression per subgroup is expressed in mSASSS units over 2 years per one-ASDAS unit increase. Sensitivity analysis group: patients included in the study and with the following variables available: occupational activity, smoking status, education and personal income (availability of family income was not demanded because of the higher number of missing values in this variable).

†Model does not reach convergence due to a small group of patients (N=5).

ASDAS, Ankylosing Spondylitis Disease Activity Score; mSASSS, modified Stoke Ankylosing Spondylitis Spine Score.