TABLE 1

General characteristics of population and proportions of subjects with spirometric data below the lower limit of normal (LLN) (i.e. with z-score value < −1.64) and above the upper limit of normal (ULN) (i.e. with z-score value >1.64) in subjects without respiratory disease

	Men		*ECSC versus* GLI**	Women		*ECSC versus* GLI**	*Men versus* women**
Subjects n	904			1067
Age years	53.3±7.1			52.8±7.3			0.149
Age categories n (%)							0.580
40–45 years	142 (15.7)			192 (18.0)
45–50 years	186 (20.6)			228 (21.4)
50–55 years	176 (19.5)			208 (19.5)
55–60 years	192 (21.4)			211 (19.8)
60–65 years	208 (23.0)			228 (21.4)
Height (m)	0.067 (1.757)			0.067 (1.636)			<0.001
BMI kg·m⁻²	27.3±4.2			26.0±5.2			<0.001
Mean z-scores
ECSC
FVC	0.79±1.08			1.30±1.11			<0.001
FEV₁	0.37±1.06			0.51±1.00			0.002
FEV₁/FVC	−0.17±0.82			−0.25±0.85			0.039
GLI
FVC	0.18±1.00		^#,***	0.24±0.98		^#,***	0.194
FEV₁	0.01±1.11		^#,***	0.03±1.00		^#,***	0.421
FEV₁/FVC	−0.32±0.87		^#,***	−0.40±0.80		^#,***	0.064
Distribution of z-scores n (%)	<LLN	>ULN	*ECSC versus* GLI**	<LLN	>ULN	*ECSC versus* GLI**	*Men versus* women**
ECSC
FVC	12 (1.3)	189 (20.9)		4 (0.4)	387 (36.3)		<0.001
FEV₁	25 (2.8)	110 (12.2)		19 (1.8)	128 (12.0)		0.330
FEV₁/FVC	42 (4.6)	3 (0.3)		62 (5.8)	5 (0.5)		0.456
GLI
FVC	28 (3.1)	72 (8.0)	^¶,***	25 (2.3)	70 (6.6)	^¶,***	0.268
FEV₁	45 (5.0)	63 (7.0)	^¶,***	47 (4.4)	61 (5.7)	^¶,***	0.417
FEV₁/FVC	65 (7.2)	5 (0.6)	^¶,***	68 (6.4)	4 (0.4)	^¶,*	0.644

Data are presented as mean±sd or n (%), unless otherwise stated. Z-scores calculated from European Community for Steel and Coal (ECSC) and Global Lung Function Initiative (GLI) reference equations. FVC: forced vital capacity; FEV₁: forced expiratory volume in 1 s. ^#: paired t-test between z-scores obtained by ECSC and GLI equations; ^¶: Bhapkar's test between distribution of z-scores. *: p<0.05; ***: p<0.001.