Gene link to smoking addiction

By MAXINE FRITH

The key to giving up smoking may lie in genes rather than willpower, new research shows.

Some people have a defective gene which makes it harder for them to quit, scientists have found. But ironically the same gene appears to protect against emphysema, a serious smoking-related illness.

People with the gene are also more likely to be light smokers, as it takes fewer cigarettes for them to get a nicotine "high".

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 which causes persistent disruption of air flow 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 findings, published in the journal Thorax, showed that people with the CYP2A6del version of the gene were significantly more likely to be current than ex-smokers.

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 a sufficient nicotine "high".

- INDEPENDENT