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Table 1 The distributions of specific characteristics by cases and controls status

From: Combined effects of cigarette smoking, DNA methyltransferase 3B genetic polymorphism, and DNA damage on lung cancer

Variables Cases Controls  
  N = 190 (%) N = 380 (%) OR (95% CI)a
Gender
 Male 115 (60.5%) 230 (60.5%) 1.00 (0.84–1.20)
 Female 75 (39.5%) 150 (39.5%) Ref.
Age (years; mean ± SD) 65.5 ± 11.9 64.4 ± 11.8  
  ≥ 60 132 (69.5%) 252 (66.3%) 1.02 (1.01–1.04)**
 51–59 38 (20.0%) 88 (23.2%) 0.93 (0.78–1.11)
  ≤ 50 20 (10.5%) 40 (10.5%) Ref.
Smoking status
 Current or ever smokers 102 (53.7%) 118 (31.1%) 2.20 (1.84–2.63)***
 Nonsmokers 88 (46.3%) 262 (68.9%) Ref.
Pack-years smoked
  ≥ 40 65 (34.2%) 60 (15.8%) 2.46 (2.43–2.50)***
 1–39 37 (19.5%) 58 (15.3%) 1.90 (1.59–2.28)***
 0 88 (46.3%) 262 (68.9%) Ref.
Green tea consumption (cup/day)
 0 146 (76.8%) 250 (65.8%) 1.71 (1.68–1.73)***
  < 1 29 (15.3%) 54 (14.2%) 1.65 (1.38–1.98)**
  ≥ 1 15 (7.9%) 76 (20.0%) Ref.
Green tea consumption (years)
 0 146 (76.8%) 250 (65.8%) 1.32 (1.30–1.34)*
  ≤ 10 23 (12.1%) 67 (17.6%) 1.02 (0.86–1.23)
  >  10 21 (11.1%) 63 (16.6%) Ref.
Fruits and vegetables intake
  ≤ 14 48 (25.3%) 139 (36.6%) 0.80 (0.78–0.81)*
 15–20 51 (26.8%) 69 (18.2%) 1.18 (0.99–1.41)
  ≥ 21 91 (47.9%) 172 (45.2%) Ref.
Exposure to cooking fumes (hours/week)
  ≥ 3 17 (8.9%) 16 (4.2%) 1.64 (1.61–1.66)***
 1–3 19 (10.0%) 15 (4.0%) 1.85 (1.55–2.21)***
  < 1 154 (81.1%) 349 (91.8%) Ref.
Family history of lung cancer
 Yes 15 (7.9%) 6 (1.6%) 2.38 (1.99–2.84)***
 No 175 (92.1%) 374 (98.4%) Ref.
DNMT3B − 149 genotypes
 TT 183 (96.3%) 345 (90.8%) 1.62 (1.35–1.94)*
 CT 7 (3.7%) 35 (9.2%) Ref.
 CC 0 (0.0%) 0 (0.0%)  
 T allele 373 (98.2%) 725 (95.4%) 1.63 (1.21–2.18)*
 C allele 7 (1.8%) 35 (4.6%) Ref.
Histological type
 Adenocarcinoma 108 (56.8%)   
 Squamous cell carcinoma 51 (26.9%)   
 Othersb 31 (16.3%)   
  1. Abbreviation: N number; OR odds ratio; CI confidence interval; Ref. reference
  2. aData were matched by age and gender
  3. bOthers included small cell carcinoma, large cell carcinoma, mixed cell carcinoma, and unspecific malignant cell
  4. *0.01 < p < 0.05, **0.001 < p < 0.01, ***p < 0.001