Table 2

Multivariate analysis between FEV₁, BPD and asthma groups among preterm subjects

	Prebronchodilator FEV₁				Postbronchodilator FEV₁
	n	Mean (SD)	βa coeff* (95% CI)	P values	n	Mean (SD)	βa coeff* (95% CI)	P values
BPD
No	189	−0.3 (1.1)	0	<0.001	184	−0.1 (1.2)	0	<0.001
Yes	42	−1.4 (1.3)	−1.0 (−1.4 to −0.6)	<0.001	40	−1.0 (1.3)	−0.9 (−1.3 to −0.5)	<0.001
Preschool wheeze
No	133	−0.3 (1.2)	0	0.01	129	0.0 (1.2)	0	0.01
Yes	98	−0.9 (1.2)	−0.4 (−0.8 to −0.1)	0.01	95	−0.5 (1.3)	−0.5 (−0.8 to −0.1)	0.01
School age asthma
No	188	−0.4 (1.2)	0	0.22	182	−0.1 (1.3)	0	0.62
Yes	43	−1.0 (1.2)	−0.3 (−0.7 to 0.2)	0.22	42	−0.6 (1.2)	−0.1 (−0.6 to 0.4)	0.62
Teenage asthma
No	192	−0.5 (1.2)	0	0.50	187	−0.2 (1.3)	0	0.78
Yes	39	−0.6 (1.4)	0.1 (−0.3 to 0.6)	0.50	37	−0.3 (1.2)	0.1 (−0.4 to 0.5)	0.78

Adjustment was performed for all the variables in the table and the selected confounders that are: smoking during pregnancy, environmental tobacco smoke exposure during infancy, atopy, parents’ occupational level and gender. For example, analysis between FEV₁ and preschool wheeze was adjusted for the selected confounders and for BPD, school age asthma and teenage asthma.
*Coefficient for an increase of 0.1 in FEV₁.
BPD, bronchopulmonary dysplasia.