April 26, 2010 -- Common gene variants affect how much a person smokes,
whether one becomes a smoker, how hard it is to quit, and risk of lung cancer
from smoking, new studies find.
The studies, based on genetic information collected by an international
consortium from more than 140,000 people of European descent, expand on a
2008 report linking a specific region of the genome to smoking behavior.
Overall, the effects of the genetic variations are small:
A single variation in the part of the genome previously linked to smoking
behavior affects how much a person smokes. It increases smoking by one
cigarette a day for each gene
carrying the variant DNA.
Two newly found gene variants
increase smoking by about half a cigarette a day for each gene carrying the
Although the effects on smoking quantity may be small, gene variants appear
to play a very large role in whether a smoker gets lung cancer.
In their 2008 study, Thorgeir E. Thorgeirsson of Iceland's deCODE Genetics
and colleagues calculated that gene variants increase a smoker's risk of lung
cancer by 30%.
Now the Thorgeirsson team, in collaboration with University of North
Carolina researcher Helena Furberg, PhD, and colleagues, calculate that the
newly found gene variants increase a smoker's odds of getting lung cancer by
And these aren't the only genetic effects:
A variation in a different part of the genome appears to make it 6% more
likely that a person will take up smoking.
Another gene variant gives a smoker a 12% better chance of quitting smoking
than a smoker who doesn't carry the variation.
Although the findings are interesting, they don't give smokers any reason to
seek genetic testing.
"At this time, testing for these variants will not tell you anything
meaningful about your risk of smoking or nicotine dependence," Furberg says in
a news release.
That may change in the future.
"Smoking is bad for anyone's health. It is even worse for some," deCODE
executive chairman Kari Steffansson says in a news release. "Today's
discoveries continue to strengthen our ability to identify who those people are
and give them a compelling additional reason to quit."
The Furberg and Thorgeirsson studies -- together with a third study by
University of Oxford researcher Jason Z. Liu and colleagues -- appear in the
April 25 online edition of Nature Genetics.