Effect of public smoking ban in Helena, Montana

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     EDITOR—As a cancer researcher who has published extensively on the harmful effects of smoking, I am in favor of vigorous smoking bans. However, the study by Sargent et al, claiming that the six month smoking ban in Helena, Montana, was associated with an immediate 40% drop in heart attacks must be viewed with scepticism.1

    Admissions for acute myocardial infarction during six month periods June-November before, during (2002), and after smoke-free3 ordinance was implemented in Helena alone on 5 June 2002

    Firstly, the researchers had no information on whether exposure to second hand smoke changed as a result of the ban. They also did not present any information on whether smoking habits were affected by the ban. If the study was concerned to isolate an effect of second hand tobacco smoke, it should have been restricted to the 33% of the study population who were never smokers.

    Secondly, the drop in heart attacks is based on very few cases: four per month on average during the ban, compared with seven per month before. Because of these small numbers the reported difference could easily be due to chance or to some uncontrolled factor.

    Finally, the "immediate effect" should make anyone stop and question the connection the authors are asserting. There are few interventions in public health that have such an immediate impact. Even if all active smokers in Helena had quit smoking for at least a year, one would not expect to see such a dramatic effect.

    The attempt to make claims about the effects of smoking bans based on this very weak ecological study raises disturbing questions about our ability to distinguish between sound science and wishful thinking.

    Geoffrey Kabat, epidemiologist

    16 Bon Air Avenue, New Rochelle, NY 10804, USA gck1@optonline.net

    Competing interests: None declared.

    References

    Sargent RP, Shepard RM, Glantz SA. Reduced incidence of admissions for myocardial infarction associated with public smoking ban: before and after study . BMJ 2004;328: 980-3. (24 April.) (文章出处：《英国医生杂志》)