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Table 1 Population characteristics for baseline and follow-up studies. Mean ± standard deviation or N (%)

From: The dynamics of smoking-related disturbed methylation: a two time-point study of methylation change in smokers, non-smokers and former smokers

 

Baseline

Follow-up

 

Current

smokers

Former smokers

Never

smokers

P-value*

Current

smokers

Former smokers

Never

smokers

P-value*

N

280

449

615

–

207

523

614

–

Males (%) #

0.57

0.64

0.35

< 2.2e-16

0.55

0.64

0.35

< 2.2e-16

Age (years) ##

50.8 ± 7.8

54.7 ± 8.8

55.1 ± 9.0

< 1e-7

57.1 ± 7.0

61.5 ± 8.9

62.2 ± 9.0

< 1e-7

Body mass index (kg/m2) ##

27.1 ± 4.5

28.1 ± 4.5

27.6 ± 4.3

< 1e-3

27.2 ± 5.0

28.5 ± 4.9

27.9 ± 4.5

< 0.05

Alcohol consumption (g/day) ##

20.2 ± 25.9

20.5 ± 23.1

13.1 ± 18.2

< 1e-7

18.2 ± 24.3

19.1 ± 22.2

12.1 ± 17.1

< 1e-7

Duration of smoking (years) ##

31.4 ± 9.3

17.0 ± 10.6

–

< 2.2e-16

36.8 ± 10.6

20.7 ± 12.9

–

< 2.2e-16

Average intensity of smoking (cig/day)

14.9 ± 10.9

–

–

–

12.6 ± 9.0

–

–

–

Time since quitting smoking (years)

–

19.9 ± 10.8

–

–

–

23.1 ± 13.6

–

–

  1. *P-value of test for equality between the groups (current smokers, former smokers, never smokers)
  2. # P-value for equality between groups determined by the chi-square test for independence
  3. ## P-value for equality between groups determined by the Kruskall-Wallace test by ranks