Well colour me surprised. Yet another “gateway” study from the US. A study that of course generates ridiculous headlines such as – E-cigarettes ‘encourage teenagers to try tobacco’: Warning that vaping is a ‘gateway’ after growing numbers try who have never smoked before. Now of course, it is entirely feasible that a never smoker tries e-cigs and then moves on to smoking, but that doesn’t necessarily mean that all kiddiwinkles that try vaping are going to do the same.
Is it a big worry? Probably not in all honesty as, simply put, kids try stuff. You could make the argument (which to be fair is relatively weak) that if e-cigs didn’t exist those that would have tried them would instead try smoking instead. Again not necessarily. Possible, most definitely. But not something that can be reliably determined.
So what is all the fuss about?
Well it is this study, conducted by a Dr Jessica Barrington-Trimis, a Postdoctoral Scholar-Research Associate at the University of Southern California (USC) Tobacco Center of Regulatory Science (TCORS). This Dr Barrington-Trimis thusly concludes:
E-cigarette use in never-smoking youth may increase risk of subsequent initiation of cigarettes and other combustible products during the transition to adulthood when the purchase of tobacco products becomes legal. Stronger associations in participants with no intention of smoking suggests that e-cigarette use was not simply a marker for individuals who would have gone on to smoke regardless of e-cigarette use.
Interestingly, she claims that those who would never have smoked tried e-cigarettes and potentially had stronger associations for taking up smoking. But does the paper support such a claim?
Well, let’s have a look shall we? Starting of course with the selection of participants – enrolled in the Southern California Children’s Health Study (CHS), completing an evaluation questionnaire in 11th or 12th grade. The study designer did try to provide a bit of balance here (not much, but some) in that any e-cigarette use at evaluation, they matched never-smoking e-cigarette users against a sample of never-smoking, never e-cigarette users to complete the follow-up questionnaire.
What strikes me here is the number of participants that were dropped out. At the start of the study there were 2097 participants, at the end there was only 298. Which is a substantial loss of participants. Even more telling (for a “gateway” study) 390 were excluded because they already had history of smoking. Obviously, having any number of that 390 moving away from tobacco to vaping would be contrary to the pre-defined conclusion. They then “randomly selected” 213 ‘never smoker/never e-cigarette users’ to 213 ‘never smoking/e-cigarette users’ – or specifically, “attempted to contact” – whereupon they lost a further 123 participants – more from the never smoking/e-cigarette users than the never/never group. A further 5 users didn’t fully complete the follow-up questionnaire.
Interestingly, the authors do not mention the loss of 390 participants in the paper, which lends itself to being more agenda driven science than an actual fact-finding exercise.
Of course, the whole “susceptibility” thing is relative and wide open to interpretation – yet the author tries to define it as “the absence of a firm commitment not to smoke” – in other words, if the participant answered “definitely not” to any of the following questions:
- At any time in the next year, do you think you will use these products?
- Do you think in the future you will experiment with these products?
- If one of your best friends were to offer you these products would you use them?
Ignoring for a moment the definition of “user” (the atypical past 30 day measure) the authors then try to lay the 2014/2015 data out in such a way that would lead you to believe that vapers did actually go on to smoke, but of course that is exactly what they want you to believe. For example, there were 61 e-cigarette users (F) in 2014, and the way the data is laid out (table 2) suggests that 24 went on to smoke – considering that the authors presented the data based on “matching factors” – such as gender, ethnicity or grade level.
The authors did try to present the data for their “gateway” hypothesis in a different way:
- Non E-Cigarette use at initial assessment to non-cigarette use at follow-up: No EC use to no cigarette use 136 (89.5%) (out of 152)
- Non E-Cigarette use at initial assessment to cigarette use at follow-up: No EC use to cigarette use 16 (10.5%) (out of 152)
- E-Cigarette use at initial assessment to non-cigarette use at follow-up: EC use to non-cigarette use 87 (59.6%) (out of 146)
- E-Cigarette use at initial assessment to cigarette use at follow-up: EC use to cigarette use 59 (40.4%) (out of 146)
So out of 152 participants that never smoked or vaped the majority stayed off both, while out of 146 that were e-cigarette users 59 went on to try other combustible tobacco products. Of course, it is worth reiterating how the US defines “use” at this point:
Participants who had “never tried” a product (not “even 1 or 2 puffs”) were classified as “never users.” Those reporting an age at first use of each tobacco product were classified as “ever users” of that product.
Seems a bit wooly to me, unlike the usual US definition of “use” which to them one or two puffs (i.e. experimentation) equals use.
According to the study, e-cigarette users were 5.49 times as likely to “initiate cigarette use” (despite no “history” of smoking – i.e. not in the past 30 days) and 7.50 times more likely than never users. Of course, the big mis-understanding here is how an individual views risk – if they try one product, they are likely to try another. This is borne out in the study text:
36.2% (n = 34) of e-cigarette users and 5.7% (n = 7) of never e-cigarette users reported initiation of cigarettes at follow-up (not susceptible = 9.69; 95% CI: 4.02–23.4; Table 3). In contrast, among those who were classified as susceptible to smoking at initial evaluation, e-cigarette users were only slightly more likely to initiate cigarette use at follow-up (47.1%
v. 32.1%; ORsusceptible = 2.12; 95% CI: 0.79, 5.74; interaction P = .03).
Broadly speaking, those who never smoked (and never used e-cigs), some of them took to smoking (self reported in the last 30 days of course) and some e-cigarette users did the same, but the kicker is in the highlight – e-cigarette users were only slightly more likely to initiate cigarette use at follow-up. Based on a relatively small sample size of course which means only 24 (out of 146 remember) had tried or used a cigarette in the past 30 days at follow-up. Of course this definition of “use” does not extend to the entire year interval, it is only the last 30 days at each questionnaire.
There was also zero associations between “cigarette initiation” and the various demographics (age, sex, education) or whether the participants had friends/family that smoked.
Out of the small sample size (146) cigarettes initiation at follow-up was indeed the most popular among the sample – all 18 of them, yet 14 of never e-cigarette users went on to smoke, as did 16 of the same group go on to use hookah. 23 never e-cigarette users went on to try any combustible tobacco product (compared to 27 that were e-cig users). Hardly damning evidence of a “gateway” theory. Nor does it support the media soundbite (emphasis mine):
Dr Jessica Barrington-Trimis, a research associate at the University of South California and lead author of the U.S study, warned vaping was ‘eroding the progress made over the last several decades in tobacco control’.
Think the media might also want to do some fact checking :
Some 5,490 pupils in southern California – where the minimum age to buy e-cigarettes was raised from 18 to 21 last month – were questioned about their smoking and vaping habits over the past decade for the study, which was published in the journal Pediatrics.
The very first figure in the study throws that quote out the window, especially considering only 298 response were finally analysed – out of 2097. Of course, it’s not like these particular researchers have any form in this area.
A previous study by the same researchers found teenagers who experimented with e-cigarettes were six times more likely to try regular cigarettes within a year, compared to those who have never vaped.
But don’t forget this important point (probably the only point I wholeheartedly agree with):
In these adolescents, the availability of e-cigarettes use may have delayed the initiation of smoking among those who would
have gone on to smoke anyway.
It is also possible that e-cigarette users who initiated smoking were more likely to be experimenting with cigarettes and less likely than other initiators to progress to regular cigarette use and nicotine dependence.
Which is of course borne out in the study text – there were never e-cigarette users / never smokers that went on to try “other combustible tobacco” products along with e-cigarette users who did the same – hardly ground-breaking research, nor is it exactly damning for e-cigarettes either.
For the final kicker:
Finally, because the rate of initiation of cigarette use in never e-cigarette users was low in our Southern California population (10.5% based on 16 new users), the odds ratio associated with e-cigarette use was not precisely estimated. However, the associations were large and highly statistically significant.
That’s after taking into account, gender, ethnicity, grade and parental education, there was no odds ratio calculated for never e-cig users taking up smoking. Again, the author is determining that social, familial, gender, educational factors have a bearing on whether or not someone is likely to take up smoking. Which is of course, part of life. A lot changes in a year of someone’s adolescence.
What this study adds:
Adolescents who reported e-cigarette use had more than six times the odds of initiating cigarette use as never e-cigarette users. These findings suggest e-cigarette use may increase the risk of smoking during the transition to adulthood.
Kids who try stuff, try stuff.
Let us not also forget the type of study, two questionnaires separated by 12 months, coupled with not asking the right questions (deliberately of course) gives the average Joe Public the perception that e-cigarettes are a bad thing. But of course, studies like this are never about health.