July 11, 2008 -- Smokers under age 17 who've inherited common genetic variations may be much more likely to face a lifetime of tobacco addiction.
Researchers have found that European-Americans who begin daily smoking at an early age are at greater risk for long-term nicotine addiction if they carry a specific genetic variation within a certain gene cluster.
The findings suggest that preventing tobacco use in early adolescence could have a large impact on a person's long-term smoking behavior. According to the American Lung Association, nearly 6,000 children under age 18 start smoking every day. About 4.5 million adolescents in the U.S. are cigarette smokers.
Robert B. Weiss, PhD, of the department of human genetics at the University of Utah School of Medicine, and colleagues tested the theory that common genetic variations affecting nicotine receptors in the nervous system would influence a person's risk of nicotine addiction.
They analyzed smoking habits and DNA samples of three European-American populations of 2,827 long-term smokers. The participants were divided into two groups: Early-onset smokers, who began daily cigarette use before age 16, and late-onset smokers, who started daily smoking at age 17 or older. Previous research has shown that this age cutoff is appropriate for evaluating the differences between early and late nicotine addiction, according to background information in the journal article.
The study revealed than in people of European origins, one variation raises the risk for tobacco dependence, while another protects against it.
Teens who began smoking before or at age 16 and who inherited two copies of the high-risk variation sequence had a 1.6-fold to nearly fivefold increase in their risk for adult nicotine addiction.
However, presence of the high-risk variation did not significantly influence smoking behaviors in people who began lighting up after age 16.
People who started smoking at a young age who carried the protective genetic variation had a lower risk of adult heavy nicotine dependence.
The study only involved people of European-American descent, but researchers say the genetic variations likely would be seen in other populations.
"We know that people who begin smoking at a young age are more likely to face severe nicotine dependence later in life. This finding suggests that genetic influences expressed during adolescence contribute to the risk of lifetime addiction severity produced from the early onset of tobacco use," Weiss says in a news release.
The identification of a common genetic risk factor in young daily smokers highlights the importance of public health efforts to combat teen smoking, Weiss says.
"Identifying this interaction ... indicates how genetics can augment public health approaches to the problem of smoking-related illness, because the risk is amenable to intervention," he writes in the journal article. "Identification of genetically high-risk individuals who would benefit from proactive interventions, such as adolescent education and cessation clinics, may result in a population with a lower rate of adult nicotine addiction."
The findings appear in the July 11 issue of PLoS Genetics.