A candidate gene approach identifies the CHRNA5-A3-B4 region as a risk factor for age-dependent nicotine addiction.
People who begin daily smoking at an early age are at greater risk of long-term nicotine addiction. We tested the hypothesis that associations between nicotinic acetylcholine receptor (nAChR) genetic variants and nicotine dependence assessed in adulthood will be stronger among smokers who began daily nicotine exposure during adolescence. We compared nicotine addiction-measured by the Fagerstrom Test of Nicotine Dependence-in three cohorts of long-term smokers recruited in Utah, Wisconsin, and by the NHLBI Lung Health Study, using a candidate-gene approach with the neuronal nAChR subunit genes. This SNP panel included common coding variants and haplotypes detected in eight alpha and three beta nAChR subunit genes found in European American populations. In the 2,827 long-term smokers examined, common susceptibility and protective haplotypes at the CHRNA5-A3-B4 locus were associated with nicotine dependence severity (p = 2.0x10(-5); odds ratio = 1.82; 95% confidence interval 1.39-2.39) in subjects who began daily smoking at or before the age of 16, an exposure period that results in a more severe form of adult nicotine dependence. A substantial shift in susceptibility versus protective diplotype frequency (AA versus BC = 17%, AA versus CC = 27%) was observed in the group that began smoking by age 16. This genetic effect was not observed in subjects who began daily nicotine use after the age of 16. These results establish a strong mechanistic link among early nicotine exposure, common CHRNA5-A3-B4 haplotypes, and adult nicotine addiction in three independent populations of European origins. The identification of an age-dependent susceptibility haplotype reinforces the importance of preventing early exposure to tobacco through public health policies.
Weiss
Robert B
RB
Department of Human Genetics, Eccles Institute of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah, United States of America. Bob.Weiss@genetics.utah.edu
Baker
Timothy B
TB
Cannon
Dale S
DS
von Niederhausern
Andrew
A
Dunn
Diane M
DM
Matsunami
Nori
N
Singh
Nanda A
NA
Baird
Lisa
L
Coon
Hilary
H
McMahon
William M
WM
Piper
Megan E
ME
Fiore
Michael C
MC
Scholand
Mary Beth
MB
Connett
John E
JE
Kanner
Richard E
RE
Gahring
Lorise C
LC
Rogers
Scott W
SW
Hoidal
John R
JR
Leppert
Mark F
MF
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D015331:Cohort Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D021122:Protein Subunits / Q000235:genetics; D011978:Receptors, Nicotinic / Q000235:genetics*; D012307:Risk Factors; D012907:Smoking / Q000235:genetics*; D014029:Tobacco Use Disorder / Q000208:ethnology / Q000235:genetics*; D044465:White People / Q000235:genetics
D009419:Nerve Tissue Proteins; D021122:Protein Subunits; D011978:Receptors, Nicotinic; C447158:CHRNA5 protein, human; C447159:CHRNB4 protein, human