Japanese researchers have found that the number of cigarettes a smoker gets through could be influenced by genetic variations that affect the way the body deals with nicotine. The findings, to be published in the European Respiratory Journal, suggest that the more quickly people break down nicotine, the more cigarettes they tend to smoke. The scientists, based at Keio University in Tokyo, studied different versions of the CYP2A6 gene, which makes a key liver protein.
The team studied 200 Japanese smokers aged 50 or over who had smoked at least one pack of cigarettes daily for ten years. They found that people who smoked least were more likely to have one of three different versions of CYP2A6, all of which make a less active version of the protein. The researchers think that people with these variants have high levels of nicotine in their blood for longer after smoking a cigarette, thus reducing the need for another.
In contrast, people with a different version of CYP2A6 get rid of nicotine more quickly, and so need to light up more frequently. The scientists found that participants who had inherited two copies of this gene variant (one from each parent) were the heaviest smokers, getting through around two packs a day. The team say their findings could help improve nicotine replacement therapies that aim to help people stop smoking, by tailoring the programme to a person's genetic make-up.
Another recent study, carried out by scientists based at the University of Toronto, confirms that different versions of the CYP2A6 gene affect the nicotine levels people receive when using nicotine patches. The findings, published in the journal Molecular Psychiatry, suggest that people with the more 'active' form of the gene will need more patches to succeed. 'If you can identify an individual who metabolises nicotine faster you can treat them more effectively', US expert Sharon Murphy told New Scientist magazine. 'Even two to three patches is way better than the cigarettes', she added.