Gene link to smoking addiction

Trying to kick a nagging nicotine habit may be tougher for some people than others, says a new study by a team of Japanese scientists who suggest that a certain gene might be responsible for the inability of some smokers to quit.

The study, published in the July issue of Thorax, a leading journal in respiratory medicine.

Scientists in Japan took DNA from 203 current or ex-smokers with suspected chronic obstructive pulmonary disease (COPD) and compared it with DNA from 123 healthy volunteers.

COPD is a combination of chronic bronchitis and emphysema that causes persistent disruption of airflow in and out of the lungs.

The researchers, led by Dr Hidetoshi Nakamura from Keio University in Tokyo, noted the number of cigarettes people smoked a day, and the length of time they had smoked.

Those who had quit were asked how long it had been since they had a cigarette.

Scientists have already identified a gene, which assists breakdown of nicotine in the body.

However, the Japanese scientists have now identified a mutant version of the gene, called CYP2A6del, which makes it harder for this breakdown to occur, and therefore makes it more difficult to quit.

The scientists wrote: “The prolonged presence of nicotine in the circulation may inhibit subjects with this defective allele [gene variant] from withdrawing their dependence on nicotine when they try to quit smoking.

“In future, the CYP2A6 genotype should be determined when nicotine replacement therapy is considered because the nicotine concentration in the blood is expected to differ in smokers with different genotypes.”

For the same reason, the gene mutation would lead people to be light smokers. They would not need to consume very many cigarettes to get sufficient nicotine “high”.

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