FOCUS: Controversy reigns over the effects on the heart of passive smoking. Until this has been resolved, the results of important studies on heart disease will be fogged by uncertainty

Even second-hand cigarette smoke is bad for your heart, a major study in The New England Journal of Medicine concluded earlier this year. No surprises there. But in addition to publishing the authors' estimate of how dangerous passive smoking is, the journal took the unusual step of running an editorial in the same issue that appeared to rubbish the research findings.

According to the researchers, from Tulane University in New Orleans, nonsmokers exposed to environmental tobacco smoke (ETS) face a 25 per cent increased risk of coronary heart disease. The dissenting editorial writer, John Bailar from the University of Chicago, said an increased risk of such magnitude was not plausible given how dilute second-hand smoke becomes in air.

The stark disagreement in the very same issue of the journal illustrates how contentious the subject is. Tobacco companies are keen to downplay the risks, antismoking campaigners are keen to talk them up. And even respected scientists are in serious disagreement or are undecided on how much passive smoking contributes to the population's burden of heart disease.

Researchers such as Richard Doll at the University of Oxford, one of the world's leading authorities on smoking and health, admits the jury is still out. In the face of this, many doctors say it would be prudent for people to minimise their exposure to cigarette smoke-especially if they already have symptoms of coronary disease.

But for researchers investigating other causes of heart disease, the uncertainty surrounding passive smoking is a real problem. How can you measure how significant other factors, such as diet, genetics and exercise, are in causing heart disease, when you don't know how much allowance to make for passive smoking? '"/>

Contact: Claire Bowles
claire.bowles@rbi.co.uk
44-171-331-2751
New Scientist
26-May-1999