The impact of methylation quantitative trait loci (mQTLs) on active smoking-related DNA methylation changes

Clinical Epigenetics

Table 1 Study population characteristics in discovery and validation panels (mean values (SD) for continuous variables and n (%) for categorical variables)

Characteristics	Discovery panel	Validation panel	p value
N	581	368
Age (years)	61.0 (6.3)	61.1 (6.4)	0.809
Sex (male)	241 (41.5%)	117 (31.8%)	< 0.001
Smoking status			0.864
Current smoker	108 (18.6%)	65 (17.7%)
Former smoker	173 (29.8%)	119 (32.3%)
Never smoker	300 (51.6%)	184 (50.0%)
Pack-years of smoking^a
Current smokers	34.6 (18.2)	33.1 (18.2)	0.250
Former smokers	22.0 (17.5)	19.4 (15.5)	0.033
Smoking cessation time (years)^b	16.5 (11.3)	17.2 (10.2)	0.742
Body mass index^c			0.248
Underweight or normal weight (< 25.0)	143 (24.7%)	116 (31.5%)
Overweight (25.0–< 30.0)	290 (50.2%)	151 (41.0%)
vObese (≥ 30.0)	145 (25.1%)	101 (27.5%)
Alcohol consumption^d			0.509
Abstainer	194 (36.3%)	128 (38.0%)
Low	301 (56.4%)	188 (55.8%)
Intermediate	30 (5.6%)	17 (5.0%)
High	9 (1.7%)	4 (1.2%)
Physical activity^e			0.058
Inactive	109 (18.8%)	82 (22.3%)
Low	245 (42.2%)	176 (47.8%)
Medium or high	227 (39.0%)	110 (29.9%)
Prevalence of CVD at baseline^f			0.621
Prevalent	86 (14.8%)	58 (15.8%)
Prevalence of diabetes at baseline^g			0.617
Prevalent	86 (14.9%)	60 (16.6%)
Prevalence of cancer at baseline
Prevalent	33 (5.7%)	22 (6.0%)	0.744

^aFor subgroups of former and current smokers; data missing for 38 and 24 participants, respectively, in discovery and validation panels; a pack-year was defined as having smoked 20 cigarettes per day for 1 year
^bFormer smokers only, data missing for 5 and 2 participants, respectively, in discovery and validation panels; cessation time equals age at recruitment minus age at cessation
^cData missing for 3 participants in discovery panel
^dData missing for 47 and 31 participants, respectively, in discovery and validation panels. Categories defined as follows: abstainer, low [women, 0–< 20 g/d; men, 0–< 40 g/d], intermediate [20–< 40 g/d and 40–< 60 g/d, respectively], high [≥ 40 g/d and ≥ 60 g/d, respectively]
^eCategories defined as follows: inactive [< 1 h of physical activity/week], medium or high [≥ 2 h of vigorous or ≥ 2 h of light physical activity/week], low (other)
^fCVD cardiovascular disease. Data missing for 1 participant in discovery panel
^gData missing for 5 and 7 participants, respectively, in discovery and validation panels

ISSN: 1868-7083