Table 1– Characteristics of participants by surfactant protein (SP)-B genotype

Characteristics	All	SP-B genotype
		rs1130866 (1580T>C)				rs2077079 (-18A>C)				rs3024791 (-384G>A)
		TT	TC	CC	p-value	AA	AC	CC	p-value	GG	GA	AA	p-value
Participants	10231 (100)	2963 (29)	5138 (50)	2130 (21)		3815 (37)	4860 (48)	1556 (15)		7724 (75)	2319 (23)	188 (2)
Females	56	45	45	43	0.49	45	44	44	0.86	44	44	48	0.50
Age yrs	59 (45–69)	58 (44–69)	59 (45–69)	58 (45–69)	0.49	59 (45–69)	58 (45–69)	59 (45–69)	0.76	58 (45–69)	59 (45–69)	59 (41–68)	0.38
Smoking
Never	24	25	23	24	0.15	25	24	23	0.18	24	24	24	0.97
Ever	76	75	77	76		75	76	77		76	76	76
Smoking exposure pack-yrs	24 (10–40)	23 (10–39)	24 (10–40)	24 (10–40)	0.48	24 (10–40)	24 (10–40)	23 (10–40)	0.49	24 (10–40)	23 (10–38)	25 (11–38)	0.59
Passive smoking	79	79	79	79	0.71	79	79	80	0.86	79	79	82	0.83
Occupational exposure to dust/fumes	17	17	17	17	0.84	18	17	17	0.12	18	17	15	0.46
Education					0.86				0.39				0.09
None	23	23	23	23		23	24	21		24	21	24
<3 yrs	52	52	52	51		52	52	53		52	52	50
>3 yrs	25	24	25	25		25	25	25		24	27	26
Occupation					0.97				0.46				0.23
Unemployed	9	9	9	9		9	10	8		9	9	12
Employed	80	81	81	80		81	80	82		80	82	81
Self-employed	10	9	10	10		10	10	9		10	9	7
Asthma	6	6	6	7	0.39	6	6	5	0.35	6	6	10	0.08
COPD
GOLD stage II	9	9	9	9	0.53	9	10	9	0.26	9	9	6	0.23
GOLD stage III–IV	4	5	4	4	0.21	4	4	4	0.86	4	4	7	0.16

Data are present as n (%), % or median (interquartile range), unless otherwise stated. The p-values were calculated by Kruskal–Wallis test for continuous variables and Pearson's Chi-squared test for categorical variables. Pack-yrs of tobacco smoked were based on ever-smokers. Passive smoking was defined as affirmative responses to the questions “Does anyone in your household smoke?” or “How many hours per day are you subjected to passive smoke?” Occupational exposure to dust or smoke was defined as an affirmative response to the question “Have you been exposed to occupational dust or fumes?” Asthma was defined as an affirmative response to the question “Do you have asthma?” COPD: chronic obstructive pulmonary disease; GOLD: Global Initiative for Chronic Obstructive Lung Disease.