A new study published in the American Journal of Public Health is being used by e-cigarette opponents to conclude that the use of e-cigarettes actually impedes the smoking cessation process.
(See: Sutfin EL, et al. The impact of trying electronic cigarettes on cigarette smoking by college students: a prospective analysis. American Journal of Public Health; June 11, 2015. doi: 10.2105/AJPH.2015.302707.)
The study followed 271 college smokers who, at baseline, had never used an e-cigarette for a three-year period. The probability of remaining a smoker at the final interview was compared between smokers who tried electronic cigarettes in the interim an those who did not. The study reported that the odds of continued smoking at wave 6 (the final study wave) were 2.5 times higher for smokers who had tried e-cigarettes. The study concludes that: "Trying e-cigarettes during college did not deter cigarete smoking and may have contributed to continued smoking."
Stan Glantz touted this study as showing that e-cigarette use impedes smoking cessation. He wrote that the study result: "adds to the evidence that e-cigarette use is depressing quitting smoking cigarettes."
The Rest of the Story
There are several reasons why this study (and similar ones) cannot be used to conclude that e-cigarettes make it more difficult to quit smoking.
The most important reason is that there is a severe problem of confounding. In this case, the confounder is lack of confidence in one's ability to quit smoking and/or nicotine use completely. We know that e-cigarette users are much more likely than other smokers to feel unable to quit smoking or quit nicotine use. In fact, the primary reason why many smokers are attracted to e-cigarettes is that they have tried to quit and failed using traditional methods and e-cigarettes provide an alternative that does not necessarily require them to quit nicotine use altogether. And it doesn't necessarily require them to quit smoking completely either.
But we also know that lack of self-efficacy (lack of confidence in one's ability to quit smoking) is a strong predictor of not being able to quit. Therefore, in an observational study such as this one, smokers who try e-cigarettes are, by definition, going to have lower rates of smoking cessation simply because they have lower levels of self-efficacy to quit.
Thus, rather than demonstrating that e-cigarettes impede smoking cessation, what this study actually shows is that smokers who choose to try e-cigarettes have much less confidence in their ability to quit (which explains their subsequent lower rates of smoking cessation).
Another major problem with this study is that it only measured one-time use of e-cigarettes in the past six months. Thus, anyone who merely tried an e-cigarette once in the past six months was included as having tried to make a quit attempt using e-cigarettes. The smoker may not have had the slightest interest in quitting. He may have simply been curious about what vaping feels like. Yet that smoker's failure to quit would be counted as a failure of e-cigarettes.
Furthermore, the study was not restricted to smokers who used e-cigarettes with any intention of quitting. How can e-cigarettes impair a quit attempt if the smoker is not even making a quit attempt. In fact, we have no information whatsoever on the reason that the e-cigarette users in this study were trying these products, how often they were using them, and whether they were indeed trying to quit by using these products.
You can easily see from these points that the results of the present study cannot be used to conclude that e-cigarettes "depress" smoking cessation.
I, however, am depressed because it is sad to see the rigor of the science in tobacco control degraded to such a degree. I believe that our desire to demonstrate a pre-determined and desired conclusion is overriding our care and rigor in interpreting scientific data.
The only way to truly answer this research question is to conduct a randomized trial. By randomizing smokers to receive either e-cigarettes or a traditional therapy (such as the nicotine patch), one ensures that the levels of self-efficacy to quit smoking and to quit nicotine use are equivalent among both groups. Then, and only then, can one make a valid comparison of the differences in quit rates between the two groups.
Unfortunately, only one randomized trial has been conducted. In that study, by Bullen et al., electronic cigarettes were found to be just as effective as the nicotine patch for smoking cessation. This is absolutely not consistent with the conclusion that e-cigarettes impede smoking cessation.
Clearly, there is an urgent need for more randomized trials to test the efficacy of e-cigarettes in smoking cessation and to compare them to traditional therapies, like nicotine replacement therapy.
But until that time, e-cigarette opponents must stop using the results of these observational studies, which are not even designed to compare smoking cesation rates betweeen groups, as evidence that e-cigarettes depress smoking cessation.