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Table 1 Descriptive characteristics of the study population

From: DNA methylation and smoking in Korean adults: epigenome-wide association study

Characteristics (mean ± standard deviation or n (%))

Genome-wide methylation analysis in blood DNA (the Korean COPD cohort)

Transcriptome analysis in lung tissue (Asan Biobank)

Never smoker (N = 39)

Former smoker (N = 30)

Current smoker (N = 31)

Male

6 (15.4)

30 (100)

30 (96.8)

188 (100)

Female

33 (84.6)

0 (0)

1 (3.2)

0 (0)

Age, years

72.9 ± 6.1

74.1 ± 7.4

71.5 ± 5.3

64.2 ± 8.7

Body mass index, kg/m2

23.2 ± 3.0

23.5 ± 2.7

22 ± 2.8

NA

Pack-year

NAc

28.9 ± 19.6

35.7 ± 19.1

42.0 ± 20.6

Duration of smoking cessation, years

NA

17.6 ± 7.5

NA

NA

Urine cotinine, nmol/L

88.4 ± 3.2d

167.6e

29421 ± 21947

NA

Undetectablea

36 (92.3)

29 (96.7)

0 (0)

NA

COPDb

19 (48.7)

20 (66.7)

21 (67.7)

98 (51.9)

  1. aUrine cotinine levels ≤56.8 nmol/L are marked as “undetectable” from the measurement using IMMULITE 2000 Immunoassay System (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA)
  2. bChronic obstructive pulmonary disease
  3. cNot available
  4. dUrine cotinine levels in three never smokers were detectable
  5. eUrine cotinine level in only one former smoker was detectable and the level was 167.6 nmol/L