Gene Variant May Decide Who Smokes and for How Long

Smokers were 8 times more likely than never-smokers to report 'buzz' with first cigarette

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FRIDAY, Aug. 8, 2008 (HealthDay News) -- A gene variant that may influence a person's initial response to smoking and lifetime smoking habits has been identified by a team of researchers.

The finding about the variant in the CHRNA5 nicotine receptor gene may help explain how someone goes from trying their first cigarette to becoming a long-term smoker.

Previous studies have inked variations in the same genetic region to a smoker's level of nicotine dependence, to the number of cigarettes smoker per day, and to an increased risk of lung cancer.

This new University of Michigan-led study examined genetic and smoking data from 435 people, including never-smokers -- who tried at least one cigarette but no more than 100 cigarettes in their lives -- and regular smokers who'd smoked at least five cigarettes a day for at least the past five years.

The regular smokers were far more likely than never-smokers to have less common form of the CHRNA5 gene in which just one base pair in the gene sequence is different from the more common form of the gene. Smokers were also eight times more likely than never-smokers to have got a pleasurable buzz when they tried their first cigarette.

The study was published online Aug. 8 in the journal Addiction.

"It appears that for people who have a certain genetic makeup, the initial physical reaction to smoking can play a significant role in determining what happens next," senior author Ovide Pomerleau, a professor of psychiatry at the University of Michigan Medical School and founder of the U-M Nicotine Research Laboratory, said in a prepared statement.

"If cigarette smoking is sustained, nicotine addiction can occur in a few days to a few months. The finding of a genetic association with pleasurable early smoking experiences may help explain how people get addicted -- and, of course, once addicted, many will keep smoking for the rest of their lives," he said.

The variant (rs16969968) of the CHRNA5 gene identified in this study explains only a portion of smoking behavior, noted Pomerleau and colleagues. More information about how genes interact with social influences and other environmental factors is needed to achieve a more complete explanation of why people smoke and why it's so difficult to quit.

Making a connection between behavioral patterns in smoking to individual genotypes will require analysis of extensive data about behavior, genes and environmental influences, Pomerleau said.

More information

The U.S. Centers for Disease Control and Prevention has more about smoking and tobacco use.

SOURCE: University of Michigan Health System, news release, Aug. 8, 2008


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