News Release

Risk of lung cancer from passive smoking may have been overstated

Peer-Reviewed Publication

BMJ

Reanalysis of epidemiological evidence on lung cancer and passive smoking

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Previous studies examining the effect of passive smoking on lung cancer, may have overstated the risk, say statisticians from the University of Warwick in this week's BMJ.

Research analysing the findings of 37 trials in this field has previously found that there is an increased risk of lung cancer of nearly a quarter (24 per cent) in people exposed to passive smoke. Professor John Copas and Dr Jian Qing Shi argue that this research may have been skewed by "publication bias" and that in reality the excess risk of lung cancer in those exposed to passive smoke is in fact lower.

Publication bias occurs when studies that have positive findings are more likely to be written up, submitted to a journal and published than those that have negative results. This means that when a review of all research in a certain field (such as the effect of passive smoke on lung cancer) is conducted, the reviewers are only able to analyse the studies which are likely to have positive results. Smaller studies or those that were never published because they had negative findings are therefore not included in the analysis and so the overall picture is skewed.

Copas and Shi say that this is what they believe to have happened with previous attempts to ascertain the risk of lung cancer from passive smoking. In a reanalysis of the 37 trials and taking account of publication bias, they conclude that the increased risk of lung cancer from passive smoking is more likely to be around 15 per cent as opposed to 24 per cent. They therefore suggest that previous levels of risk should be interpreted with caution.

Contact:

Professor John Copas, Department of Statistics, University of Warwick, Coventry

Tel: +44(0)2476 523370
Email: jbc@stats.warwick.ac.uk

Or

Dr Jian Qing Shi

Tel: +44 (0)2476 523523 ext 26322
Email: shi@stats.warwick.ac.uk

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