(See: Gmel G, Baggio S, Mohler-Kuo M, Daeppen JB, Studer J. E-cigarette use in young Swiss men: is vaping an effective way of reducing or quitting smoking? Swiss Med Wkly. 2016 Jan 11;146:w14271. doi: 10.4414/smw.2016.14271. eCollection 2016.)
Here is the abstract of the study:
"QUESTION UNDER STUDY: To test longitudinally differences in conventional cigarette use (cigarettes smoked, cessation, quit attempts) between vapers and nonvapers.
METHODS: Fifteen months follow-up of a sample of 5 128 20-year-old Swiss men. The onset of conventional cigarette (CC) use among nonsmokers, and smoking cessation, quit attempts, changes in the number of CCs smoked among smokers at baseline were compared between vapers and nonvapers at follow-up, adjusted for nicotine dependence.
RESULTS: Among baseline nonsmokers, vapers were more likely to start smoking at follow-up than nonvapers (odds ratio [OR] 6.02, 95% confidence interval [CI] 2.81, 12.88 for becoming occasional smokers, and OR = 12.69, 95% CI 4.00, 40.28 for becoming daily smokers). Vapers reported lower smoking cessation rates among occasional smokers at baseline (OR = 0.43 (0.19, 0.96); daily smokers: OR = 0.42 [0.15, 1.18]). ..."
CONCLUSIONS: We found no beneficial effects of vaping at follow-up for either smoking cessation or smoking reduction."
On his blog, Stan Glantz touted this as being "another big well-done study" and summarized its findings:
- "Nonsmokers at baseline who used ecigs were more likely to be smokers one year later than nonsmokers who did not use e-cigs; and
- Smokers at baseline who used e-cigs were less likely to have quit smoking a year later."
The Rest of the Story
Dr. Glantz and the paper itself are completely misrepresenting the nature of the study's findings, and as a result, drawing conclusions that are not supported by the actual findings.
The study presents itself as being longitudinal in nature. It also presents itself as comparing changes in smoking from baseline to follow-up among vapers compared to non-vapers. Similarly, Dr. Glantz insinuates that the paper is comparing longitudinal changes over time between vapers and non-vapers.
There is a major flaw in this representation of the study methods and findings. It is hidden in the fine print of the methods section, and it is only mentioned once in the paper. So if you are not extremely careful, it is something that you could easily miss.
The flaw is related to the way in which "vaping" was measured in the study. According to the methods section:
"At follow-up, participants were asked whether they had used ECs in the previous 12 months."
That's it. That is the complete description of how the most important variable in the study - vaping - was measured.
There are two fatal problems with this approach.
First, the study fails to establish the baseline vaping status of each participant. To qualify as a true longitudinal design, the study would identify vapers and non-vapers at baseline and then follow both groups over time to compare changes in smoking status over the follow-up period. Instead, the study measures - at follow-up - whether the participants had used an electronic cigarette any time in the past year. They could have used an e-cigarette for the first time the previous day, for example, and would still be considered as vapers in the analysis.
Thus, the study is essentially cross-sectional in nature. It does not compare the changes in smoking over time between vapers and non-vapers. What it does is measure, at a single point in time, past year smoking changes as one variable and ever use of e-cigarettes in the past year as the other variable. But the key problem is that they study methods do not allow the investigators to determine which came first. Because it is a cross-sectional study, it is impossible to know whether the change in smoking status preceded the use of electronic cigarettes or whether the use of electronic cigarettes preceded the smoking status change.
Both the study itself and Dr. Glantz make the assumption that the use of electronic cigarettes preceded the smoking status changes. But there is no way to make such a determination. The fact that the study authors and Dr. Glantz are making this assumption creates the appearance of a strong investigator bias. They appear to have made a pre-determined conclusion that vaping leads to smoking initiation and impedes smoking cessation. Thus, when faced with a choice about whether the e-cigarette preceded or followed the smoking status changes, they simply assume - without any evidence - that the e-cigarette use must have preceded the smoking status change.
This assumption is flawed because there is no way to determine the time course of the e-cigarette use vs. the change in smoking status based on the single survey question that assessed e-cigarette use.
By assuming that the e-cigarette use preceded the changes in smoking status, the paper authors and Dr. Glantz are able to misrepresent the study as showing that vaping leads to progression to smoking among baseline nonsmokers and impedes smoking cessation among baseline smokers. But the truth is that the findings could be presented in the exact opposite way. It is possible that the progression to smoking is what led baseline nonsmoking participants to try electronic cigarettes (perhaps because they wanted to quit or decrease their health risks after initiating smoking). And it is also possible that the success or failure in quitting smoking is what led baseline smoking participants to either try or not try e-cigarettes. Those who quit smoking would of course have no reason to try an e-cigarette. But those who failed to quit would be very likely to look for an alternative, and e-cigarettes are one of the most popular alternatives available.
In other words, it is entirely possible that the baseline nonsmokers who started smoking did so prior to using electronic cigarettes. To conclude, instead, that the baseline nonsmokers must have started smoking prior to vaping (despite knowing only that these participants had used an electronic cigarette at some point during the past 12 months, but not necessarily at baseline) is not science. We don't do that as researchers. When we have two highly plausible explanations for study findings, we don't choose the explanation that we like the best or which supports our pre-ordained conclusions. This is not scientific because you are just drawing whatever conclusion you want without evidential support. To choose one explanation over the other, one would at very least have to possess empirical evidence to support that choice. And this is precisely why we don't draw causal conclusions from cross-sectional studies in which the timing of the exposure and outcome are not clear.
If you read the paper or Stan Glantz's account of it, you get the impression that the study compared people who at baseline were either vapers or non-vapers and then followed them over time to compare changes in their smoking behavior. But the study did not assess vaping at baseline. Nor did it assess vaping at any point during the follow-up period. It only assessed whether the participants had used an e-cigarette at some point during the study period. Thus, the presentation of the study results is deceptive.
The second fatal flaw is that the question used to assess vaping behavior only asked about ever use of e-cigarettes. It does not assess the frequency of use or its duration. According to the methodology, participants were merely asked whether they had "used" e-cigarettes at any point in the past 12 months. But the term "used" was not clarified. Vapers, as defined in the study, included anyone who so much as tried one e-cigarette. It is entirely possible that many of the participants who the study called vapers were actually not vapers at all, but merely people who had tried an e-cigarette. They may have even tried the e-cigarette, hated it, and never tried another one. Given this limitation, how can the study possibly conclude that vaping led to smoking initiation or impeded smoking cessation?
If this is a "well-done study," I'd hate to see what a poorly conducted study looks like.
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