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Table 1 Study population characteristics*

From: Modification of additive effect between vitamins and ETS on childhood asthma risk according to GSTP1 polymorphism : a cross -sectional study

Parameter Total ETS (+) ETS (−) P-value
n 1111 403 708  
Age (years) 9.48 ± 1.73 9.54 ± 1.68 9.44 ± 1.76 0.384
Sex (male/female) 577/529 366/337 211/192 0.925
BMI 18.46 ± 3.30 18.77 ± 3.48 18.28 ± 3.18 0.024
Parental history of asthma 38/875 (4.3 %) 14/315(4.4 %) 24/560(4.3 %) 0.912
Parental history of AR 347/885 (39.2 %) 109/322(33.9 %) 238/563(42.3 %) 0.014
Parental history of AD 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
  FEF25–75% (%) 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
  1. AR allergic rhinitis, AD airway disease; BMI body mass index, ETS environmental tobacco smoke, FVC forced vital capacity, FEV1 forced expiratory volume in 1 s, FEF 25–75% forced expiratory flow during the middle half of FVC
  2. *Values are mean ± SD or n (%)