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expert reaction to modelling study on electronic cigarettes in the US

Publishing in PLoS One, scientists report that based on the existing scientific evidence related to e-cigarettes and optimistic assumptions about the relative harm of e-cigarette use compared to cigarette smoking, e-cigarette use currently represents more population-level harm than benefit.


Dr Lion Shahab, Senior Lecturer Epidemiology & Public Health at UCL, said:

“Modelling of outcomes is crucially dependent on the initial assumptions being made. The authors make some very speculative assumptions here, particularly on the ‘gateway’ effect in teenagers – they assume that vaping leads to smoking.  The trouble is, all their data on this comes from studies that don’t prove anything of the sort, and ignore the possibility that e-cigarettes could actually be driving kids away from tobacco.

“This leads to a biased result which flies in the face of data in the US, where smoking among kids continues to decline – just like in the UK.  If this new study were correct, those rates would be going up.  The authors’ estimate of ‘life years lost’ is primarily driven by their overestimate of e-cig use contributing to a significant increase in the uptake of smoking in kids.

“In my opinion, the authors’ choice of studies used to justify the impact of e-cig use on quitting rates is rather biased.  In at least one case they have used a paper whose methodology has previously been heavily criticised.

“If you’re going to make assumptions, a much more reasonable approach would be to assume e-cigarettes are at least as effective as things like patches or gum – that is what the very best evidence from proper randomised controlled trials shows.  Unfortunately the authors of this study modelled using wrong assumptions – and, unsurprisingly, they’ve ended up with the wrong conclusions.”


Prof Peter Hajek, Director of the Tobacco Dependence Research Unit at Queen Mary University of London, said:

“This new ‘finding’ is based on the bizarre assumption that for every one smoker who uses e-cigs to quit, 80 non-smokers will try e-cigs and take up smoking.  It flies in the face of available evidence but it is also mathematically impossible.  In the UK alone, 1.5 million smokers have quit smoking with the help of e-cigarettes. The ‘modelling’ in this paper assumes that we also have 120 million young people who became smokers.

“The model only reflects whatever spurious assumptions are put into it. Starting with the opposite assumptions would generate the opposite result.  This is no route to a scientific finding.

“In reality there is no evidence, from any country, that vaping lures young non-smokers to smoking (let alone in huge numbers). In the USA, the country where the authors live and whose smoking statistics they should know, smoking in young people has been declining at an unprecedented rate.

“Vaping is helping smokers quit, and there is no evidence that it lures children to smoking. It may even be deflecting young people who would otherwise smoke away from cigarettes.”


* ‘Quantifying Population-Level Health Benefits and Harms of E-Cigarette Use in the United States’ by Samir Soneji et al. published in PLoS One on Wednesday 14 March 2018.


Declared interests

Prof Peter Hajek: No conflicts.

No others received.

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