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Several people have emailed asking for our reaction to the “Expert reaction to meta-analysis looking at e-cigarette use and smoking cessation” released on the website http://www.sciencemediacentre.org/expert-reaction-to-meta-analysis-looki... target="_blank";ScienceMediaCenter.org the minute that the embargo on our <em;Lancet Respiratory Medicine </em;paper lifted.&nbsp;
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The most remarkable thing about these criticisms is their generality rather than engaging the specific substance of the paper.&nbsp;
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Careful readers will find that the paper considers all these issues (and more), including extensive discussion of the limitations of the available data.&nbsp;
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Despite these limitations, it is possible to draw important conclusions based on the available studies.
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In particular, we conducted a formal sensitivity analysis of the factors (and other factors) that the experts raise, which appears in Table 2 of the paper.&nbsp;
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None of the factors that the "experts" raise affected the overall conclusion of the analysis that smokers who use e-cigarettes are less, not more, likely to stop smoking.
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Here are our responses to the experts’ comments:
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<strong;Prof. Robert West, Professor of Health Psychology, UCL, said:</strong;
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“If use of e-cigarettes caused fewer smokers to quit, the quit rate in England would have decreased as use of e-cigarettes has increased. Data from The Smoking Toolkit Study – a large ongoing population survey of smoking in England – shows, if anything, the opposite (http://www.smokinginengland.info/";www.smokinginengland.info).
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&nbsp;“Publication of this study represents a major failure of the peer review system in this journal.”
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Cigarette use rates have been declining since the 1970s in the UK, prior to the introduction of e-cigarettes.&nbsp; Simply comparing rates of cigarette and e-cigarette use does not allow for evaluation of the association between e-cigarette use and quitting. &nbsp;
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<strong;Prof. Linda Bauld, Professor of Health Policy, University of Stirling; Deputy Director, UK Centre for Tobacco and Alcohol Studies; Chair in Behavioural Research for Cancer Prevention, Cancer Research UK, said:</strong;
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“E-cigarettes have been called a ‘distruptive technology’ not just because of the controversy they have created but also because they pose significant challenges for research. The current paper represents the latest attempt to bring together the existing literature on e-cigarettes for smoking cessation. While its breath is to be commended, its conclusions (that e-cigarettes don’t work for smoking cessation) are at best tentative and at worst incorrect. The main reason for this is that attempting to directly compare the results of a body of literature that uses such a wide range of study designs and includes such variable (and often poorly defined) populations and outcomes is difficult, if not impossible. Some of the observational studies included in the review, in particular, suffer from a range of limitations that don’t allow us to reliably assess whether e-cigarettes help smokers quit.
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The goal for this systematic review and meta-analysis was to be comprehensive in terms of the included literature.&nbsp; We recognize there is variation in study design; these differences are summarized in Table 1, evaluated in the sensitivity analysis (Table 2), and discussed in detail in the appendix.&nbsp; In the current regulatory environment, e-cigarettes are not prescription medicines that are only available for use in supervised smoking cessation attempts.&nbsp; In addition, e-cigarette use outside a quit attempt can still affect quitting behavior.&nbsp; The relationship between e-cigarette use and smoking cessation is important in all these situations.&nbsp; Most important, as the sensitivity analysis showed, these differences do not materially affect the conclusion in the paper.
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“For example, these studies: don’t properly assess whether participants have used e-cigarettes enough to make a difference for smoking cessation (such as including measures of ‘ever’ rather than ‘regular’ use);&nbsp; may be biased in how participants in the studies were selected (i.e. not representative of e-cigarette users in the population): and, perhaps most importantly, have confounding factors including that smokers in the studies are these who have tried to quit many times in the past and may therefore be more likely to try the remaining new product&nbsp; (e-cigarettes), or that they gave up using these devices early in the conduct of the study but were still included in the final results with the assumption that e-cigarettes didn’t ‘work’ for them whereas there could be multiple reasons why they stopped using the devices.
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Table 1 and the detailed descriptions of the studies in the appendix describe what potential confounders were considered in the different studies.&nbsp; Our sensitivity analysis showed that whether e-cigarette use was defined as current use or ever use did not significantly affect the results.
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“Some of the more recent studies included in the review do point to the types of measures that should be used to assess e-cigarettes for smoking cessation. These categorise the type of device (as e-cigarettes are many products not one product), look carefully at when and for how long e-cigarettes were used, and ask whether participants were using them to stop smoking or for other reasons. These more carefully conducted studies shed light on how e-cigarettes could help smokers stop – for example if they contain sufficient nicotine, are used often and for long enough, and are more advanced (‘tank’) devices than earlier ‘ciga-like’ e-cigarettes. However, the current review does not separate out these studies or draw these distinctions but treats the body of evidence as a consistent and comparable set of studies when in fact it is not.
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The studies of more intensive users of e-cigarettes and users of higher generation devices were specifically discussed in the Discussion as populations who might have increased rates of smoking cessation.&nbsp; It is important to emphasize that these people represent a small fraction of all e-cigarette users.&nbsp;
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“The review also omits an important part of the picture when assessing any benefits of e-cigarettes in helping smokers quit – and that is the sheer reach of these devices. They are now the most popular aid to stopping smoking in the UK, for example, used by over 2.6 million people. Even low quit rates (which, it has to be said, are also found for licensed smoking cessation aids like Nicotine Replacement Therapy) for groups in studies could translate to many smokers quitting when applied at the population level.
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The fact that e-cigarettes are popular as quit aids does not make them effective.&nbsp; The overall conclusion from all the available data suggests that e-cigarette use is depressing quitting.
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“Other systematic reviews of the literature on e-cigarettes for smoking cessation are underway as this is such a rapidly moving area of research. These should not repeat the mistake of this current review which is to not take account of the huge variability in the characteristics of e-cigarette users, the devices themselves, and patterns of use. Alternative, more carefully conducted, reviews are needed if&nbsp; we are to provide health professionals and, most importantly, smokers with high quality information about the circumstances in which e-cigarettes may help people to move away from the more deadly alternative – combustible tobacco.”
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We look forward to reading these studies when they are published.&nbsp; We hope that such studies are not simply limited to e-cigarettes used under “ideal” conditions, but rather are studied as actually promoted and used in the real world.
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<strong;Rosanna O’ Connor, Director of Tobacco, Alcohol & Drugs, Public Health England, said:</strong;
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“There are over a million ex-smokers using an e-cigarette in Britain and we need to provide those who continue to smoke with accurate, balanced information on different quitting methods.
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“Evidence from practice in England shows that two out of three smokers who combined e-cigarettes with additional expert support from a local stop smoking service quit successfully and while dual use is a complex issue, many vapers report using an e-cigarette to cut down and ultimately quit. Smokers who have struggled to quit in the past could try vaping, and we encourage vapers to take that next step and stop smoking completely.”
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Our paper is based on all the available data as of the time we wrote the paper.&nbsp;
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<strong;Peter Hajek, Director of the Tobacco Dependence Research Unit, Queen Mary University of London (QMUL), said:</strong;
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“This review is grossly misleading in my opinion. There are several problems with the way studies were selected and used, but the main flaw is simple, though not easy to spot. The studies that are presented as showing that vaping does not help people quit only recruited people who were currently smoking and asked them if they used e-cigarettes in the past.&nbsp; This means that people who used e-cigarettes and stopped smoking were excluded.&nbsp; The same approach would show that proven stop-smoking medications do not help or even undermine quitting.
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The studies included are divided into study type and time of e-cigarette assessment in longitudinal studies.&nbsp; The sensitivity analysis showed no significant difference in the results based on whether e-cigarette use was assessed at baseline or at follow-up.&nbsp;
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“Here is an analogy: Imagine you recruit people who absolutely cannot play piano. There will be some among them who had one piano lesson in the past. People who acquired any skills at all are not in the sample, only those that were hopeless at it are included. You compare musical ability in those who did and those who did not take a lesson, find a difference, and report that taking piano lessons harms your musical ability. The reason for your finding is that all those whose skills improved due to the lessons are not in the sample, but it would not necessarily be obvious to readers.
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The methods and interpretations in our paper follow standard statistical methods for analyzing and interpreting data.
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“E-cigarettes are a major development in public health. It is unfortunate that their potentially huge positive impact is being hindered by excessive regulations triggered by misleading suggestions.”
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As our paper concludes, the evidence to date indicates that smokers who use e-cigarettes are less, not more, likely to stop smoking.&nbsp;
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<strong;Prof. Ann McNeill, Professor of Tobacco Addiction, National Addiction Centre, Institute of Psychiatry Psychology & Neuroscience, King’s College London (IoPPN), said:</strong;
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“This review is not scientific. The information included about two studies that I co-authored is either inaccurate or misleading. In addition, the authors have not included all previous studies they could have done in their meta-analysis. I believe the findings should therefore be dismissed. I am concerned at the huge damage this publication may have – many more smokers may continue smoking and die if they take from this piece of work that all evidence suggests e-cigarettes do not help you quit smoking; that is not the case.
The problems with the authors’ interpretation of the two papers mentioned above are as follows: The first study (Adkson&nbsp;<em;et al</em;) is not longitudinal as has been reported here – e-cigarette use was measured at follow up, the same time as quit status was ascertained. The second study (Hitchman&nbsp;<em;et al</em;) included smokers who were using e-cigarettes at baseline and therefore included smokers who may have tried to use e-cigarettes to quit and failed, and excluded smokers who successfully used e-cigarettes to quit. The authors of this meta-analysis had been previously informed by the authors of the Adkison paper that they were misreporting the findings.”
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In the Adkison study, the measurement of cigarette use was longitudinal (from one wave to another), while the assessment of e-cigarette use was at follow-up.&nbsp; For the longitudinal studies, the paper was clear about the time of e-cigarette assessment, i.e. whether it was at baseline or follow-up (Table 1 and the discussion of individual studies in the appendix).&nbsp; The results in the Hitchman study, like any such study, are based on the behavior reported during the time of the study.&nbsp;&nbsp;&nbsp; In any event, the sensitivity analysis did not show an effect of the timing of e-cigarette measurement on results. &nbsp;

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