Part Nine
Future Perspectives
In this section of the Report the Committee wishes to identify certain topics where recent research is suggesting new health effects of smoking. Mention is made of the putative association between paternal smoking and childhood cancers and also the changes in histological patterns in lung tumours. The introduction of bupropion as a new therapeutic aid to smoking cessation is recorded. New developments relating to the declared content of tobacco, and regulation of its use, are briefly noted and then the section closes with a mention of recent research on nicotine receptors.
Paternal Smoking and Childhood Cancers
9.1 A putative association between cancer in children and paternal smoking at the time of their conception has been proposed in studies based on the Oxford Survey of Childhood Cancers119,120,121 and a large case-control investigation from Shanghai.122 The Committee examined the published papers. Certain limitations were noted, but it was agreed that there were plausible hypothetical mechanisms whereby paternal smoking at the time of conception could induce an increase in cancers in the offspring. It is therefore important that future developments in this area are followed.
Changes in Histological Patterns in Lung Tumours of Smokers
9.2 Changes in the incidence of lung cancer in several parts of the world have been accompanied by corresponding changes in their histological type. Squamous and small cell carcinomas, arising from the larger bronchi, are traditionally associated with smoking, but relative and absolute increases in the incidence of adenocarcinomas of the lung have been increasingly recognised. A recent study from Switzerland123 demonstrates rising incidence rates for adenocarcinomas in both younger men and women in the early 1990s, the rates being more than 3-fold higher than for squamous carcinomas in the same groups. This alteration in histological pattern almost certainly reflects changes in the pattern of exposure of bronchial tissues to tobacco-associated carcinogens. Smokers of modern low-tar filtered cigarettes tend to compensate by increasing the number and depth of puffs, the peripheral parts of the lung are thus more exposed to larger amounts of tobacco-associated carcinogens, and it is in the peripheral parts of the lung that adenocarcinomas develop. The diagnostic and therapeutic implications of an increase in lung adenocarcinomas are likely to be considerable.
New Pharmacological Aid to Smoking Cessation
9.3 A potentially important development in pharmacological aids to smoking cessation has been the recent approval in the USA of the anti-depressant drug bupropion. Preliminary data from clinical trials indicate that bupropion, whose mode of action in not well understood, possesses efficacy as an aid to cessation, and that its combination with nicotine patches works better than either drug alone. This opens up intriguing possibilities for research into brain mechanisms underlying nicotine addiction and for further work to test effects on ongoing smoking and withdrawal.
Tobacco Product Information and Regulation
9.4 The Committee had often expressed concern that smokers were not given detailed information about the constituents of tobacco smoke. They were therefore pleased to note the undertaking, given by the European Commission at the Health Council meeting in December 1997, that the Labelling Directive and the Tar and Nicotine Content Directive would be reviewed.
9.5 In the United States the Food and Drug Administration has recently been given authority to regulate tobacco as a drug. This raises important questions about possible action to regulate tar (or specific tar components), nicotine and gas phase emissions from cigarettes, as well as allowing competition on a more rational basis between the pharmaceutical industry and the tobacco manufacturers. Currently the pharmaceutical industry is strictly regulated in respect of preparations of nicotine and other novel nicotine delivery devices whereas the tobacco industry can launch a new cigarette with the minimum of controls. These issues need consideration in the UK, including the possible establishment of a regulatory authority to control nicotine and tobacco products.
Nicotine receptor research
9.6 Research reported recently in Nature,124 has provided strong evidence that a particular subtype of the high-affinity neuronal nicotinic acetylcholine receptor is critical to the reinforcing properties of nicotine. Genetically altered mice lacking the beta 2 subunit of this receptor showed little desire to self-administer nicotine. This discovery might in future lead to the possibility of new pharmacological approaches to the treatment of nicotine addiction.
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