Understanding the new West et al. paper on e-cigarettes and smoking cessation

Today Robert West’s research group will publish[*] in his journal, Addiction, a study about success rates for smokers’ most recent cessation attempt, as a function of what cessation aid, if any, they used. The results are further information that puts the lie to the claim that e-cigarettes are not helping people quit smoking. However, the way the results are already being interpreted by laypeople, and how they will inevitably be reported in the future is not accurate. Note that this post is about how to properly interpret the scientific meaning of the study. It is not about the policy implications of the results, and most definitely not about whether spinning the results in a particular way useful or proper in pursuit of a particular political goal.

[*At the time I am writing this, though probably not by the time you read it, this verb tense is correct. In an example of a very disturbing trend in academic publishing, this study was made available to the press in advance of making it available to scientists who could review it. This results in reporters rushing to write stories and asking for comments of researchers who have not even read the paper, much less had a chance to assess it. The reporters want to run whatever quick story they can the moment the embargo is lifted (the first minute the paper appears in the journal) – or in this case even before the embargo is lifted, since the stories are already running. Since most of the scientific community has not had a chance to peer review the paper before their stories run, the only comments they can offer are uninformed, and thus the reporters have nothing to work with other than the assertions in the press release. And, yes, in case it is not obvious: The fact that I am writing this before the paper is officially out means that I have a bootleg copy of it in advance – but I only got it after the first press reports already appeared, and many of those who are commenting on it already apparently have not seen it at all.]

The study is very similar to a 2008 study by Brad Rodu and myself (which, strangely, is not cited in West et al., even though it is – to my knowledge – by far the most similar study in the literature to date). In that study, Brad and I looked at the method employed by smokers (Americans, c.2000) in their most recent quit attempt. We found that those who attempted to quit by switching to smokeless tobacco were by far more likely to have succeeded than those using any other cessation aid. In the new study, West et al. did the same thing for British smokers who used either e-cigarettes or NRT. Both studies also looked at those who quit unaided.

As with our study, those using tobacco harm reduction (THR; i.e., switching to a low-risk alternative to smoking) were more likely to have quit smoking than the others. It turns out that the success rate for those using smokeless tobacco was much more impressively higher in our study than those using e-cigarettes in West’s, though for the reasons explained below, not too much should be read into that.

The West study is being interpreted as showing something like “e-cigarettes are 60% better for smoking cessation than NRT” based on a comparative rate of successful cessation among those using the particular products. This is undoubtedly true – indeed, it is probably a gross understatement: NRT barely works, if at all, while e-cigarettes are tremendously effective for many people. However, that is not a proper interpretation of the study results.

The equivalent claim about Rodu and Phillips would have been “smokeless tobacco is more than 600% more effective for smoking cessation than NRT.” This would be an inappropriate conclusion and we took pains to make that clear. West et al. also are careful about phrasing their conclusions: “E-cigarette users were more likely to report abstinence than either those who used NRT bought over-the-counter…” (quoted from the abstract of the bootleg version of the paper I have).

The reason that this is not the same as saying “X% more effective” is embedded in the quoted sentence, in the reference to the people themselves. People choose the cessation method that they think will be most effective for them. They do not always assess this correctly, of course, but there is clear self-selection. The misinterpretation “X% more effective” is based on the common error of treating people as if they were molecules – all the same. This is an attitude that is all too common among many people working in tobacco research (though, I do not believe, among any of the authors of the papers mentioned here), and a simplification that is inevitable in laypeople’s interpretation of the science (unless they are severely warned against it).

In the case of Rodu and Phillips, we can be fairly sure that most those who switched to smokeless tobacco had, at the time they decided to quit smoking that way, already tried it and decided they liked it enough to switch to it. Moreover, many of them were probably among the small (at the time) portion of the population that understood that smokeless tobacco was low risk. Thus, they were much more likely to succeed for reasons that had more to do with the people than the product per se. Indeed, it is a safe bet that if those who quit using NRT or some other method had been handed smokeless tobacco and told to try to quit by switching to it, very few would have done so – far fewer than actually quit using their chosen method.

The situation with the West results is almost certainly not so extreme, but the same principle applies. Those who switched to e-cigarettes were those who chose to try to switch to e-cigarettes. Many had already tried them and decided they were appealing. Though the number who had not previously tried is probably higher than the switchers who had never tried smokeless tobacco in Rodu-Phillips, in both cases everyone who tried to switch was willing to switch. Many of the would-be quitters were not willing to switch.

Similarly, those who tried to use NRT included those who believed that using NRT was a good way to quit. One reason for the poor performance of NRT among such people is that they have been convinced by aggressive marketing that NRT will magically make them not want to smoke anymore after they taper off of the NRT. For most smokers, that is not true. NRT is a viable substitute for smoking, as a THR product, for some smokers. Getting a bit of aid to get away from smoking forever is just what a (very) few smokers need. But for the most part, NRT does not perform as marketed. That aside, the people who chose NRT rather than e-cigarettes intentionally did not choose e-cigarettes, suggesting that they did not think the latter was the best option for them.

The issue becomes even more clear when we compare those who quit unaided, as most ex-smokers did. Smokers who are genuinely ready to quit all tobacco products forever just quit. That is why the method is so successful – because it is self-selected by those who know they do not want a substitute and do not need a magical drug to make them no longer want to smoke. Giving such people any of the substitutes or other cessation aids would not necessarily increase their cessation rate at all. West et al. had somewhat richer data than did Rodu and I, and thus were able to show that those who quit unaided had a slightly lower score on a “strength of urges to smoke” index, just as we would predict.

To sum up the implications of this: It is not an accurate interpretation of cessation success data to say that a particular method is better, generically and across the population. An extreme possibility illustrate this. The following is consistent with the study results:

  • Those who quit smoking using NRT consisted of every single individual in the study sample for whom that would have been successful. That is, the use of NRT was successfully selected by everyone for whom it would work, and no one who did not try it would have succeeded in quitting had they tried it.
  • But for the unsuccessful quitters who did not try e-cigarettes (those who tried NRT or unaided cessation, but kept smoking), e-cigarettes would have often been successful. That is, had those unsuccessful quitters been handed an e-cigarette and told “try this instead”, many more of them would have quit smoking

Under that hypothetical (which, again, is perfectly consistent with the study results), we would say that e-cigarettes are enormously more effective for smoking cessation than the “60% more” that is the common misinterpretation of the results.

Note that this is not an argument for running clinical trials, in which everyone is forced to try a particular method, to avoid these complications. That is a tempting solution to the self-selection problems. But clinical trials introduce much bigger problems, and thus are an inferior research method for smoking cessation, for reasons I have discussed at length before. Clinical trials do directly address (albeit badly) the question “which product is X% more effective across the population”. But the biggest problem with them is that this is not actually an interesting question.

Why? Because the self-selection is not a problem, but rather part of what matters in the real world. There is no possibility that every smoker in a population will be assigned one method to quit. Thus, there is no reason to try to figure out which would be the best single method to assign to everyone (which is basically what a well-done clinical study would show). Rather, in the real world, each of the cessation methods is available to everyone, and (since it does not matter which one someone uses, from the perspective of health) it is best if they can find which one works best for them (which refers to both effective smoking cessation and ongoing happiness).

So what matters from the West results and other data is the observation “people are successfully quitting using e-cigarettes.” That is an important and legitimate interpretation of the results. It is also good that many people are successfully quitting using NRT and many more are just quitting because they do not want to use any product any more. These methods are not in competition with each other, so we should not care which one works for more people. Any of them that works for anyone who wants to quit is a good thing. This is good, because there is no way to legitimately interpret the results in terms of which one works better.

18 responses to “Understanding the new West et al. paper on e-cigarettes and smoking cessation

  1. Yes, yes and yes. And no….

    NRT IS in competition with e-cigs. It’s also in competition with smokeless tobacco and every single non-medicinal pure nicotine that might exist in the future for the simple reason that regulators have decided that NRT is the only form in which smokers might access nicotine, other than through smoked tobacco (at least in the UK).

    As you know well, this is a political game, and Robert is playing the politics whilst keeping his credibility unassailably intact. Making the point that e-cigs are 60% more effective than NRT is a perfect soundbite which works well synthesising a (relatively) complex concept into a digestible chunk.

    As much as we’d all love the science PR to be accurately reflecting the science, the most important thing is that it has a real-world effect. You can’t deny that this is what’s happened today.

    Sad, but that’s the world we live in.

    • Carl V Phillips

      By “competition” in that context, I was referring to the specific goal of smoking cessation and the fact that the value of one of these methods in fulfilling this goal in no way reduces the value of another (other than merely being redundant with it, which costs nothing when measured in terms of that goal). That is why it really does not matter which is “better”, even if such a construct makes sense. The contribution of one in no way takes away from the value of another = no competition. Obviously the manufacturers of the products (between and within categories) compete with each other for sales.

      As I explicitly noted, the purpose of this post was to explain (a few aspects of) how to correctly interpret the results. I was not addressing the political value, theory of the second-best, or ethics surrounding spinning the results in ways that runs contrary to that.

  2. I don’t disagree with any of that, but the relative effectiveness of cessation methods does matter. This study doesn’t answer that question, nor does it claim to, but it does suggest that Ecigs are effective and it’s logical to then ask whether they’re more or less effective than NRT. Why? Because NRT is publicly funded (in the UK). Publicly funding one quit method introduces a need to ensure value for money. West’s study is important because it firmly establishes that, for Govt funded PH, NRT is not the only game in town.

    • Carl V Phillips

      It is true that government funding opens up another realm for rivalry. Even if it does not matter which is “best” because there is not going to be an assignment of only one to people (as with a RCT), if government gets the idea in their “mind”(?!) that they are going to fund exactly one of them, then there is an artificial rivalry introduced. If they were really going down the path of funding the one that is “best” (though I don’t think that is ever what is going to happen — they are going to fund the one that is politically connected or politically correct), then it might become necessary to figure out which is best. In that case, life becomes much more complicated. Whatever “best” is, it is clearly not just “has a better ex-smoker:still-smoker ratio among those who tried that method most recently”, as Rodu-Phillips or West et al. measures.

  3. I think you highlight an important point when you say ” -based on the common error of treating people as if they were molecules – all the same. This is an attitude that is all too common among many people working in tobacco research-” Medical intervention assumes that we are looking for a product that can be prescribed based on tested results. E-cigs work because they are one of a selection of methods a smoker can choose from.
    It switches the power from the public health provider to the consumer.

  4. Pingback: People using e-cigarettes to quit smoking 60 percent more likely to succeed than those using NRT sold over the counter « The counterfactual

  5. Carl V Phillips

    Correction: The throw-away statistic that now reads “600%” originally read “1200%”. This has no substantive implications since the point there was just “a really big number that would obviously be absurd to make claims about”, and they both qualify. The correction does tend to contribute to a couple of meta points, though: (a) As noted, Brad and I did not calculate, or even consider calculating, that statistic in our original research. Thus I had to do it as a back-back-of-the-envelope (rounding based on the “60%” at the core of this analysis — it was roughly 10x that, not 20x). (b) The need to get things like this out quickly, to try to reduce somewhat the misinterpretations others are rushing to publish, creates errors (albeit, in this case, inconsequential). Such overclocking is a terrible way to engage in scientific discourse.

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  7. Whenever the topic is “quitting” or “cessation”, I get the uncomfortable impression that everybody applies a very personal definition of these terms. Especially when talking about success or failure.

    My personal definition is that I quit smoking. But I didn’t attempt “cessation”. I simply tried e-cigs and switched to this much better tasting way to enjoy nicotine. Manifest harmreduction and increased health is incidental and very welcome. But I would still have chosen e-cigs over tobacco without the health benefits. Simply for the much greater pleasure they provide.

    Some people use “quit smoking” synonymously to “quit using nicotine” and “cessation”. I don’t. I differentiate.
    I wish the applied definition would be prominently stated in the abstract and the conclusion of any study as well as in any interview on the topic. A lot of the heat in this debate seems to come from the friction between incompatible implied definitions.

    So, I don’t feel guilty about any “filthy nicotine habit”. So what?

    Most people don’t feel guilty about their “caffeine habit” … yet. The ascetic zealots just haven’t marked them (including me) for target practice … yet. Don’t worry, once all nicotine users have been exterminated or driven underground into smoke easies to buy their moonshine tobacco, the “nasty stimulant caffeine” will be glantzed at.

  8. Pingback: Fight for Your Right to #Vape – Daily Action Plan for Wednesday, 05.20.14 | Vapers Place

  9. Pingback: Study Finds E-Cigarette Users Are More Likely to Stop Smoking Than People Who Use Other Methods to Quit - Hit & Run : Reason.com

  10. Pingback: Study Finds E-Cigarette Users Are More Likely to Stop Smoking Than People Who Use Other Methods to Quit | Michigan Standard

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  12. Pingback: New Population-Based Study Reports that E-Cigarettes Outperform NRT for Self-Assisted Smoking Cessation Among Smokers Who Choose These Approaches | Tech Electronic Smokeless NETWORK

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