Table 1 Participant characteristics from 10 study samples used for the genome-wide association study (GWAS) meta-analysis or independent replication of follow-up GWAS variants

From: Genome-wide meta-analysis reveals common splice site acceptor variant in CHRNA4 associated with nicotine dependence

Study sample

Total N

No. (%) a

No. (%), male

Mean age (s.d.)

  

Mild nicotine dependence

Moderate nicotine dependence

Severe nicotine dependence

  

GWAS meta-analysis samples

 deCODE

9090

5871 (64.6)

2074 (22.8)

1145 (12.6)

4253 (46.8)

54.2 (16.7)

 EAGLE

3006

1416 (47.1)

1027 (34.2)

563 (18.7)

2528 (84.1)

Not availableb

 COPDGene

2211

666 (30.1)

964 (43.6)

581 (26.3)

1214 (54.9)

57.7 (7.9)

 COGEND

1935

941 (48.6)

521 (26.9)

473 (24.4)

750 (38.8)

36.5 (5.5)

 SAGE*

832

243 (29.2)

295 (35.5)

294 (35.3)

465 (55.9)

39.4 (11.3)

Independent replication samples

 FTC

2374

1345 (56.7)

793 (33.4)

236 (9.9)

1314 (55.3)

45.9 (15.6)

 Yale-Penn

2116

381 (18.0)

1014 (47.9)

721 (34.1)

1247 (58.9)

37.7 (10.3)

 UW-TTURC

1534

311 (20.2)

723 (47.1)

500 (32.6)

658 (42.9)

43.1 (11.5)

 GAIN

774

327 (42.3)

280 (36.2)

167 (21.6)

389 (50.3)

53.8 (16.4)

 nonGAIN

671

298 (44.4)

234 (34.9)

139 (20.7)

349 (52.0)

52.9 (15.5)

  1. Abbreviations: COGEND, Collaborative Genetic Study of Nicotine Dependence; COPDGene, Chronic Obstructive Pulmonary Disease Gene Study; EAGLE, Environment and Genetics in Lung Cancer Etiology Study; FTC, Finnish Twin Cohort Study; GAIN, Genetic Association Information Network GWAS of schizophrenia; nonGAIN, Molecular Genetics of Schizophrenia—nonGAIN sample; SAGE*, Study of Addiction: Genetics and Environment (* indicates that overlapping COGEND participants were excluded); UW-TTURC, University of Wisconsin-Transdisciplinary Tobacco Use Research Center.
  2. aScores on the Fagerström Test for Nicotine Dependence (FTND) were used to categorize nicotine dependence as mild (FTND score 0–3), moderate (FTND score 4–6) or severe (FTND score 7–10). For deCODE only, the mild category included 1558 participants with FTND score 0–3 and an additional set of 4313 low-intensity smokers with no FTND data available but with less than 10 cigarettes per day reported.
  3. bFor EAGLE, age was only available as a categorical variable, so average age could not be calculated. The categorical age distributions were as follows: 23.2% aged 59 or less, 18.2% aged 60–64, 22.4% aged 65–69, 21.4% aged 70–74 and 14.8% aged 75–79.
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