Restrictive pulmonary function is more prevalent in patients with ankylosing spondylitis than in matched population controls and is associated with impaired spinal mobility: a comparative study

Table 5 A multiple linear regression model for 147 AS patients, dependent variable FVC%

	Crude Estimates ß^a (95% CI^b)	P-value	Adjusted estimates^c ß (95% CI)	P-value	Final model (R²)
Age	-0.3 (-0.6, -0.05)	0.02	ns		0.45
Gender					P < 0.001
Female	Reference	< 0.01	-8.2 (-12.9, -3.5)	0.001
Male	-8.3 (-14.2, -2.3)
Smoking ^d
Lifelong non-smokers,	Reference	0.33	ns
Ex-smokers and smokers	2.9 (-3.0, 8.8)
Education ^b
≤ 12 years	Reference	0.94	ns
> 12 years	0.3 (-6.3, 6.8)
ASDAS	-1.4 (-4.5, 1.7)	0.36	ns
BASFI (0 to 10)	-1.9 (-3.3, -0.5)	< 0.01	ns
BASMI (0 to 10)	-5.6 (-6.9, -4.3)	< 0.001	-4.1 (-5.4, -2.7)	< 0.001
Chest expansion (cm)	4.0 (2.8, 5.1)	< 0.001	2.7 (1.6, 3.9)	< 0.001
VO ₂ peak	0.6 (0.2, 0.9)	< 0.001	ns

^a Estimated regression coefficients, ^b confidence interval, ^c Adjusted for the other variables in the table, ^d Smoking (lifelong non-smokers vs ex-smokers and smokers). ^e Education (≤ 12 years or > 12 years), ns: not significant in the adjusted model

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