Electronic Cigarette Use and Progression From Experimentation to Established Smoking
Authors: Shannon Lea Watkins
Stanton A Glantz
Benjamin W Chaffee
Journal: Pediatrics (2018)
Discipline: CLINICAL MEDICINE
Keywords: adolescents; electronic cigarettes; conventional cigarette smoking; progression; established smoking
Affiliations: Center for Tobacco Control Research and Education, ., Departments of Preventive and Restorative Dental Sciences and., Center for Tobacco Control Research and Education., Medicine, University of California, San Francisco, San Francisco, California., Philip R. Lee Institute for Health Policy Studies, and.

Abstract:  Background: It has been shown that never-smoking adolescents who try electronic cigarettes (e-cigarettes) are at increased risk of subsequent conventional cigarette smoking. We evaluated associations between e-cigarette use and progression to established smoking among adolescents who had already tried cigarettes. Methods: Among participants (age 12-17 years) in the nationally representative Population Assessment of Tobacco and Health survey who had smoked a cigarette (≥1 puff) but not yet smoked 100 cigarettes (N = 1295), we examined 3 outcomes at 1-year follow-up as a function of baseline e-cigarette use: (1) having smoked ≥100 cigarettes (established smoking), (2) smoking during the past 30 days, and (3) both having smoked ≥100 cigarettes and past 30-day smoking (current established smoking). Survey-weighted multivariable logistic regression models were fitted to obtain odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for smoking risk factors. Results: Versus e-cigarette never use, having ever used e-cigarettes was positively associated with progression to established cigarette smoking (19.3% vs 9.7%), past 30-day smoking (38.8% vs 26.6%), and current established smoking (15.6% vs 7.1%). In adjusted models, e-cigarette ever use positively predicted current established smoking (OR: 1.80; 95% CI: 1.04-3.12) but did not reach statistical significance (α = .05) for established smoking (OR: 1.57; 95% CI: 0.99-2.49) and past 30-day smoking (OR: 1.32; 95% CI: 0.99-1.76). Conclusions: Among adolescent cigarette experimenters, using e-cigarettes was positively and independently associated with progression to current established smoking, suggesting that e-cigarettes do not divert from, and may encourage, cigarette smoking in this population. 

Retracted: No

PubPeer comments:
 The authors of this study omitted a profoundly important variable relevant to adolescent cigarette experimenters: lifetime cigarette consumption at Wave 1. There were six categories: (1) one or more puffs but never a whole cigarette, one cigarette, 2-10, 11-20, 21-50 and 51-99 cigarettes. In short, past cigarette consumption is a strong indicator of future smoking. To demonstrate the importance of this variable, we reproduced Chaffeeu2019s model and itu2019s unadjusted odds ratios (ORs), and then we added the consumption variable (Table). The results reveal that all of the elevated ORs for smoking in Wave 2 are substantially reduced after inclusion of past smoking consumption. Our analysis demonstrates that Chaffeeu2019s model is deficient, and the conclusion that e-cigarette use is u201cindependently associatedu201d with progression to smoking is mistaken. Substantial revision or retraction of this study is warranted. **Table. Odds Ratios (95% Confidence Interval) for Smoking Outcomes in the Wave 2 PATH Survey, According to E-Cigarette Use at Wave 1** **Smoked 100+ Cigarettes** | | Chaffee | Rodu Reproduction | Rodu Repro. + Wave 1 LCC | | ------------------ | ----------------- | ----------------- | ----------------- | | Never E-Cig | Referent | Referent | Referent | | E-Cig past 30 days | 2.56 (1.58 u2013 4.14) | 2.60 (1.61 u2013 4.19) | 1.21 (0.69 u2013 2.13) | | E-Cig trier:| 2.13 (1.43 u2013 3.18) | 2.16 (1.46 u2013 3.22) | 1.45 (0.88 u2013 2.38) | **Smoked Past 30 Days** | | Chaffee | Rodu Reproduction | Rodu Repro. + Wave 1 LCC | | ------------------ | ----------------- | ----------------- | ----------------- | | Never E-Cig | Referent | Referent | Referent | E-Cig past 30 days | 2.29 (1.64 u2013 3.19) | 2.12 (1.52 u2013 2.96) | 1.41 (0.998 u2013 2.00) | E-Cig trier | 1.56 (1.15 u2013 2.12) | 1.43 (1.05 u2013 1.95) | 1.09 (0.78 u2013 1.52) | **Smoked 100+ Cigarettes and Smoked Past 30 Days** | | Chaffee | Rodu Reproduction | Rodu Repro. + Wave 1 LCC | | ------------------ | ----------------- | ----------------- | ----------------- | | Never E-Cig | Referent | Referent | Referent | E-Cig past 30 days | 2.56 (1.52 u2013 4.32) | 2.55 (1.51 u2013 4.31) | 1.32 (0.75 u2013 2.30) | E-Cig trier | 2.41 (1.46 u2013 3.97) | 2.45 (1.49 u2013 4.03) | 1.70 (0.96 u2013 3.01) | Disclosure: BR is supported by unrestricted grants from tobacco manufacturers to the University of Louisville and by the Kentucky Research Challenge Trust Fund. , 
 A correction has been published, but appears unrelated to the concerns expressed above. https: pediatrics.aappublications.org content 142 3 e20181885 An error occurred in the article by Chaffee BW et al, titled u201cElectronic Cigarette Use and Progression From Experimentation to Established Smokingu201d published in the April 2018 issue of Pediatrics (2018;141[4]:e20173594; doi:10.1542 peds.2017-3594). On page 3, in Table 1, under the heading u201cOutcome: smoked 100 cigarettes and smoked during the past 30 du201d and the row u201cE-cigarette former,u201d the unweighted number of participants (n) reads: u201c406.u201d This should have read: u201c404.u201d Copyright u00a9 2018 by the American Academy of Pediatrics , 
 # Inadequate adjustment for confounding by smoking history invalidates the authors conclusions *Pediatrics* has essentially ignored the fatal criticism of this paper contained in the reanalysis by Rodu and Plurphanswat [1], which is similar to Rodu s PubPeer entry at #1 above. Further, it will not release what it claims to be a statistical review of the paper. The fact remains that the use of a more sophisticated model to adjust for confounding by smoking history eliminates the association on which the false and misleading conclusions of the paper entirely rest. As Rodu concluded in his comment: *The results in the table demonstrate that all of Chaffeeu2019s elevated ORs in Wave 2 for e-cigarette users are substantially reduced and not statistically significant after adjusting for cigarette consumption. Our analysis demonstrates that Chaffeeu2019s model is inadequate, and the conclusion that e-cigarette use is u201cindependently associatedu201d with progression to smoking is incorrect. Substantial revision or retraction of this study is warranted.* After Rodu published his critique of this paper, two comments were published on the *Pediatrics* web site and were then later removed by the editors. The first, by the authors, [2] was a response to criticisms raised by Rodu. This response contained *ad hominem* and defamatory content. The second was a reaction to the first from me, David Sweanor, David Abrams and Ray Niaura. [3] The two deleted comments, with the *ad hominem* and defamatory content removed, are reproduced below. ### 1. Electronic cigarettes, smoking progression, and statistical over-adjustment * Benjamin W Chaffee, assistant professor University of California San Francisco Other Contributors: * Shannon Lea Watkins, post-doctoral fellow * Stanton A Glantz, professor Using longitudinal data from the PATH study, we demonstrated a positive and independent association between adolescents use of e-cigarettes and progression from conventional cigarette experimentation (smoked 1 puff but not 100 cigarettes) to current established smoking (smoked u2265100 cigarettes) one year later.(1) Drs. Rodu and Plurphanswat criticized our conclusion because we did not adjust for lifetime history of cigarette consumption at baseline as a confounding variable. They demonstrated that including this variable in statistical models attenuated the association between e-cigarette use and progression to established smoking. [Deleted *ad hominem* and defamatory content] In this case, Drs. Rodu and Plurphanswat employed a statistical trick designed to reduce the strength of the association between e-cigarette use and the dependent variable (smoking 100 cigarettes) by including an adjustment variable (number of cigarettes smoked) that nearly defines the dependent variable itself. Essentially, their analysis places a form of the dependent variable on both sides of the regression equation. This critique from Drs. Rodu and Plurphanswat is akin to suggesting that a study of hypertension should adjust for confounding by systolic blood pressure. We stand by our results as reported. ### 2. The Chaffee et al response to the critique of their paper is inadequate * Clive D. Bates, Director Counterfactual Consulting Other contributors * David T. Sweanor, Chair of the Advisory Board, Centre for Health Law, Policy Ethics * David B. Abrams, Professor, Department of Social and Behavioral Sciences * Raymond S. Niaura, Professor, Department of Social and Behavioral Sciences The response of Chaffee et al to the comments of Rodu Plurphanswat is inadequate, disappointing and surprising.u2028 It is inadequate because Rodu Plurphanswat have highlighted a serious flaw in the treatment of confounding in the original paper. It is clear that the propensity to become a smoker will be better characterised by the number of cigarettes consumed in the range one puff to 99 cigarettes by an experimenter rather by assuming that all subjects in this category have the same propensity to smoke, regardless of consumption. u2028 The authorsu2019 response, alleging that a u2018statistical tricku2019 has been played, does not make any sense at all: Rodu Plurphanswat have used a straightforward statistical procedure and a more rigorous approach than the authors. Rodu Plurphanswat show that when the relationship is adjusted for the amount smoked by experimenters, the association between vaping and the onset of established smoking disappears. In other words, many of those vaping would have smoked whether or not they had vaped. This reanalysis is fatal to authorsu2019 main findings and invalidates their controversial and politically-charged conclusion that u201ce-cigarettes do not divert from, and may encourage, cigarette smoking in this populationu201d. It is disappointing because the authors, apparently with the approval of the journal, have resorted to an ad hominem attack on Rodu and without showing any improper conduct or incomplete disclosure, or that their new analysis exhibits any sort of bias or weakness. It is surprising because a neutral reader would expect a journal of the stature of Pediatrics to retract or insist on correction of such an obviously flawed paper when the flaws have been so clearly and dispassionately pointed out. ### Critique of authors response to Rodu At the end of their comment, the authors argue that the more sophisticated deconfounding undertaken by Rodu was conceptually flawed: Essentially, their analysis places a form of the dependent variable on both sides of the regression equation. This critique from Drs. Rodu and Plurphanswat is akin to suggesting that a study of hypertension should adjust for confounding by systolic blood pressure. This is incorrect, the approach to adjusting for confounding used by Rodu is perfectly reasonable and the authors argument makes no sense. The epidemiologist, Carl V Phillips wrote about the exchange in an article for a vaping-interest newspaper [4]. On the subject of the author s argument against Rodu s analysis, Phillips states: Benjamin W. Chaffee, the first author of original paper [...] posted a truly bizarre response to the Rodu and Plurphanswat comment. He suggested that including the measure of total cigarette consumption in the model was a case of including a form of the outcome variable as a predictor variable, an error that occasionally sneaks into statistical analyses. He is completely wrong, garbling the principle he is trying to cite. To explain, if there were a variable for u201csmoked in the last 50 days at follow-upu201d in the dataset, and that were included in a model where the outcome was u201csmoked in the last 30 days at follow-up,u201d that would be an error. The 50-day measure is an alternative measure of basically the same outcome. As such, it would be such a good predictor of the outcome that all other associations would disappear. However, including a measure of how close someone already was to the outcome at baseline (i.e., the first survey, not the follow-up) is not only fine, but it should definitely be done. **References** [1] Rodu B. Plurphanswat N. RE: Electronic Cigarette Use and Progression From Experimentation to Established Smoking. *Pediatrics*, 15 March 2018 [[link] ] [2] Chaffee BW et al. Electronic cigarettes, smoking progression, and statistical over-adjustment, *Pediatrics* 30 March 2018 [[Web archive] ] [3] Bates CD et al. The Chaffee et al response to the critique of their paper is inadequate, *Pediatrics*, 11 April 2018 [[Web archive] ] [4] Phillips CV. Researchers Call For Retraction Of Glantz Gateway Effect Paper, Daily Vaper, 6 April 2018 [[link] ] ,