Driven to smoke?14th April 2008
The results of two separate studies, examined in The Economist, reveal that the choices made by smokers generate serious and complex questions.
It has been proved that smoking can cause lung cancer. A question which is less commonly posed is: what makes people smoke in the first place?
A research team working at deCODE, an Icelandic organisation, tried to find out what draws people to smoke. However the results of their study, published in Nature, have not fully answered this question.
The Icelandic team said they know why some people smoke moderately while others smoke more heavily, and as a result why some smokers are, in a genetic sense, more likely to develop lung cancer.
In a study which looked at nearly 14,000 smokers in Iceland, the research team were able to show that having a single variant - known as "allele T of SNP rs1051730" - in the right position in their genetics would suggest that a person smoked heavily.
This estimate was very accurate - the researchers estimated that an incorrect answer would occur in "less than one in a thousand trillion" cases.
This variation was also strongly linked with the likelihood of a person's risk of lung cancer. Copies of the allele (inherited from the person's parents) can increase the risk by 30%.
However, a person's choice to become a smoker was not increased by having the variation.
According to another study in the journal, and one published in Nature Genetics, the idea that a person's genes make them smoke heavily and so raise their risk of lung cancer may not be accurate.
Dr Paul Brennan, from the International Agency for Research on Cancer, and Dr Christopher Amos, from the University of Texas, said that the deCODE study has shown the chromosome has important properties.
However, they said allele T impacts on "a person's susceptibility to lung cancer, rather than acting indirectly by modifying his smoking behaviour," and increases "the effects of smoking instead of the amount of smoking."
They think another allele comes into play - known as "rs8034191" - and said the fact that chromosome 15 contains two more nicotine receptive genes makes drawing conclusions more complex.
Although the doctors' studies have posed complicated and conflicting results, there is one fact which has not been disputed: "there is some sort of a link between genetics and lung cancer."
Smoking bans and accidents
Smoking bans are intended to improve public health. The US has not put a nationwide ban into place and as a result different legislation is in force across the country. One state may have a total ban, while other states may not.
Scott Adams and Chad Cotti, economists at the University of Wisconsin-Milwaukee, have said this lack of cohesion has a dangerous link to drink-driving and accidents.
In a study published in the Journal of Public Economics, they demonstrated that people who smoke drove longer distances in order to find bars to smoke in.
The study examined information from 120 American counties. 20 counties had imposed a ban on smoking.
There was a 13% rise in deaths caused by drunk-driving (in the average county with a population of 680,000). In counties where smoking had been banned for over 18 months, accidents increased by 19%.
The study connected the increase with the ban, saying smokers were driving longer distances to find bars to smoke in.
A dangerous choice
The Icelandic company, deCODE, which identified the variant genetic allele, has said that it will put rs1051730 into the screening test it provides to people who want to find out how susceptible they are to particular diseases.
In the future, people who decide to take up smoking may also be able to gauge how dangerous this decision is.
However, lung cancer is not the only danger posed by smoking. As the American study demonstrated, the combination of inconsistent legislation, alcohol and driving has proved deadly.
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