January 26, 2016

Stanton A. Glantz, PhD

Fourth longitudinal study shows that youth who use e-cigs are 3 times more likely to go on to cigarettes

James Wills and colleagues just published a very strong longitudinal study of the relationship between e-cigarette use among high school students who had never smoked a cigarette and their smoking status a year later. 
They found that nonsmoking youth who used e-cigarettes were about 3 times more likely to be smoking conventional cigarettes than youth who did not use e-cigarettes.
The study controlled for a wide range of other factors in addition to e-cigarette use that could be leading to smoking: age, gender, ethnicity, parental education, parental support and rebelliousness.  Accounting for these factors did not erase the e-cigarette effect.
Here is how the authors summed up their results:

The aim of this research was to determine whether e-cigarette use in adolescence is longitudinally related to transitions in cigarette smoking. Prospective analyses tested the effect of ecigarette use for onset of smoking, including demographic and psychosocial covariates that were themselves predictors of smoking. Results showed the probability of onset of smoking was higher among adolescents who used e-cigarettes, independent of the covariates. Sensitivity analyses indicated this finding was not dependent on a particular definition of use. We also demonstrated that several of the study variables predicted onset of e-cigarette-only use, or dual use. However, a test of whether e-cigarette use by adolescent smokers was related to reduction in their frequency of smoking did not show a significant effect.

Significantly the study it explored a wide range of levels of use at baseline from kids who only smoked e-cigarettes 1 or 2 times through those who smoke e-cigarettes every day and found that the effect of e-cigarettes on smoking was present for all levels of e-cigarette use (Table 3 in the paper).  In fact, “ever” use of e-cigarettes was the strongest predictor of smoking cigarettes a year later.
This is an important finding because e-cigarette enthusiasts have dismissed earlier research on the grounds that ever use was not a good measure of the effects of e-cigarette use. 
Another important finding in the paper is that youth who were smoking at the beginning of the study who also used e-cigarettes did not reduce their cigarette consumption a year later.
Wills and colleagues also did an impressive set of sensitivity and alternative analyses, all of which confirmed the main results in the paper.
Predictably, the English website Science Media Center immediately released the following critique of the study:

Prof. Linda Bauld, Professor of Health Policy at the University of Stirling, Deputy Director of UK Centre for Tobacco and Alcohol Studies, and Chair in Behavioural Research for Cancer Prevention at Cancer Research UK, said:
“This is the third published study from the USA suggesting that young people who have tried e-cigarettes at baseline are more likely to have tried tobacco smoking at follow up (in this case one year later).
“However, if you look more closely at the paper any assumptions that one leads to the other are not supported, as is the case with previous studies.  In particular in this paper, more frequent use (compared to experimentation) of both e-cigarettes and tobacco at baseline and follow up was low and did not significantly increase – around 8% for e-cigarettes and 4% for tobacco at both time points.
“This study does not provide evidence that e-cigarettes are a gateway to regular smoking in teenagers.  It is important that ongoing research on this topic is conducted, including in the UK, where e-cigarette age of sale laws already exist and significant marketing restrictions will be introduced from May this year.  Such measures are important to protect children, as electronic cigarettes are products for adult smokers who wish to cut down and stop smoking.”

The interesting thing is that, as with the criticisms of our recent meta-analysis showing that smokers who use e-cigarettes are less likely to quit smoking, Bauld’s criticism failed to note that Wills and colleagues anticipated and answered this criticism in their paper.  They wrote:

Note that the rate of cigarette smoking was relatively low in this population, and the majority of T1 [at the beginning of the study] ecigarette ever-users did not transition to cigarette smoking over a 1-year period. Still, we were able to detect a significant effect of e-cigarette use for increasing the likelihood of onset of smoking, and we think this has public health implications.

They are absolutely correct.  A negative result (i.e., conclusion of no effect) based on small numbers would not allow a strong conclusion.  A positive conclusion (as they found) based on small numbers is strong evidence for an effect because the statistical methods account for sample size.
Prof. Bauld also ignores the recent paper from Switzerland (of about 5500 20 year old men, which is a large sample) that also showed that e-cigarette use was associated with significantly more cigarette smoking a year later.
So, now there are four longitudinal studies all showing that e-cigs promote cigarette smoking among youth, which is precisely what the earlier cross-sectional studies said.
The full paper, “Longitudinal study of e-cigarette use and onset of cigarette smoking among high school students in Hawaii,” was published in Tobacco Control and is available here.
Here is the abstract:

Objective Use of electronic cigarettes (e-cigarettes) is prevalent among adolescents, but there is little knowledge about the consequences of their use. We examined, longitudinally, how e-cigarette use among adolescents is related to subsequent smoking behaviour.
Methods Longitudinal school-based survey with a baseline sample of 2338 students (9th and 10th graders, mean age 14.7 years) in Hawaii surveyed in 2013 (time 1, T1) and followed up 1 year later (time 2, T2). We assessed e-cigarette use, tobacco cigarette use, and psychosocial covariates (demographics, parental support and monitoring, and sensation seeking and rebelliousness). Regression analyses including the covariates tested whether e-cigarette use was related to the onset of smoking among youth who had never smoked cigarettes, and to change in smoking frequency among youth who had previously smoked cigarettes.
Results Among T1 never-smokers, those who had used e-cigarettes at T1 were more likely to have smoked cigarettes at T2; for a complete-case analysis, adjusted OR=2.87, 95% CI 2.03 to 4.05, p  
Conclusions Adolescents who use e-cigarettes are more likely to start smoking cigarettes. This result together with other findings suggests that policies restricting adolescents’ access to e-cigarettes may have a rationale from a public health standpoint.

Here are some of the stories in the media on the paper:
Daily Mail
Medical Express



The Science Media Center again can't seem to find a single "expert" who agrees with the growing evidence that e-cigarettes have a down side.
And again that mades the credibility of the Science Media Center relevant, as well as its selection and presentation of "expertise":
http://www.centerforhealthjournalism.org/2013/02/19/reporting-evidence-r... title="http://www.centerforhealthjournalism.org/2013/02/19/reporting-evidence-r......
https://www.rt.com/uk/326441-coca-cola-obesity-research/" title="https://www.rt.com/uk/326441-coca-cola-obesity-research/";https://www.rt...
http://www.sourcewatch.org/index.php/Science_Media_Centre" title="http://www.sourcewatch.org/index.php/Science_Media_Centre";http://www.so...
http://www.scidev.net/global/journalism/feature/uk-s-science-media-centr... title="http://www.scidev.net/global/journalism/feature/uk-s-science-media-centr......
http://www.prwatch.org/news/2014/04/12442/science-media-centre-spins-pro... title="http://www.prwatch.org/news/2014/04/12442/science-media-centre-spins-pro......
http://www.talkfracking.org/frackademics/frackademics-case-study-4/" title="http://www.talkfracking.org/frackademics/frackademics-case-study-4/";htt...
http://www.lobbywatch.org/profile1.asp?PrId=121" title="http://www.lobbywatch.org/profile1.asp?PrId=121";http://www.lobbywatch.o...
http://www.observa.it/uks-science-media-centre-lambasted-for-pushing-cor... title="http://www.observa.it/uks-science-media-centre-lambasted-for-pushing-cor......
Jon Krueger


 This link:
contains some further interesting quotes from Thomas Wills, and this one:
http://www.medpagetoday.com/Pulmonology/Smoking/55833";http://www.medpag... , a telephone interview with him, is enlightening. As he eloquently states:
"There has been a very vocal, somewhat nasty debate going on for several years now about whether e-cigarettes are harmful or helpful," he told <EM;MedPage Today</em;. "This debate has largely been going on in the absence of scientific evidence. We now have convergent findings suggesting that teens who vape are more likely to smoke cigarettes."
Others need to consider and reflect upon previous statements and claims regarding this key issue. For example:
Dr Farsalinos apparently insisted in Abu Dhabi last March that:
"there is not a single case of a never-smoker who used e-cigarettes and then became a smoker of tobacco cigarettes".
David Bareham


Apologies . . . the reference for the aforementioned Farsalinos quote is thus:
David Bareham


Could you please add a link or title of the other three longitudinal studies showing similar fidings. Thank you.

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