Table 1 Study population characteristics^*

1111

403

708

9.48 ± 1.73

9.54 ± 1.68

9.44 ± 1.76

0.384

577/529

366/337

211/192

0.925

18.46 ± 3.30

18.77 ± 3.48

18.28 ± 3.18

0.024

38/875 (4.3 %)

14/315(4.4 %)

24/560(4.3 %)

0.912

347/885 (39.2 %)

109/322(33.9 %)

238/563(42.3 %)

0.014

88/896 (9.8 %)

28/323(8.7 %)

60/573(10.5 %)

0.384

Maternal education

Low (≤ high school)

391/1090 (35.9 %)

162/391(41.4 %)

229/699(32.8 %)

0.004

High (> high school)

699/1090 (64.1 %)

229/391(58.6 %)

470/699(67.2 %)

Household income (10,000 Korean won)

≤299

312/1055 (29.6 %)

134/386(34.7 %)

178/669(26.6 %)

0.019

300–399

292/1055 (27.7 %)

102/386(26.4 %)

190/669(28.4 %)

≥400

451/1055 (42.8 %)

150/386(38.9 %)

301/669(45.0 %)

Paternal smoking

Non-smoker

293/1078 (27.2 %)

34/394(8.6 %)

259/684(37.9 %)

<.0001

Past smoker

263/1078 (24.4 %)

36/394(9.1 %)

227/684(33.2 %)

Current smoker

522/1078 (48.4 %)

324/394(82.2 %)

198/684(29.0 %)

Maternal smoking

Non-smoker

1075/1091 (98.5 %)

382/391(97.7 %)

693/700(99.0 %)

Past smoker

6/1091 (0.6 %)

2/391(0.5 %)

4/700(0.6 %)

0.077

Current smoker

10/1091 (0.9 %)

7/391(1.8 %)

3/700(64.2 %)

Frequency of ETS (per week)

≤ twice

85/215 (39.5 %)

2–4 times

59/215 (27.4 %)

≥5 times

71/215 (33.0 %)

Serum total IgE (kU/L)*

58.13 ± 4.01

59.45 ± 3.65

57.38 ± 4.22

0.693

Pulmonary function test*

FVC (%)

89.34 ± 1.13

89.35 ± 1.13

89.33 ± 1.14

0.982

FEV₁(%)

96.91 ± 1.13

96.86 ± 1.13

96.93 ± 1.13

0.932

FEV₁/FVC

92.12 ± 1.07

91.99 ± 1.07

92.2 ± 1.06

0.588

FEF_25–75% (%)

90.63 ± 1.38

91.89 ± 1.31

89.96 ± 1.41

0.554

Wheeze in previous 12 months

62/1069 (5.8 %)

31/386 (8.0 %)

31/683 (4.5 %)

0.019

Asthma diagnosis

110/1064 (10.3 %)

50/390 (12.8 %)

60/674 (8.9 %)

0.043