How to prove teens experiment

After the recent rush of positive news first from RSPH where they are trying to de-stigmatise nicotine and encourage vapouriser use (at the expense of throwing smokers out of pub gardens), then from ASH that once again shows that vaping isn’t a gateway to smoking which Linda Bauld discusses at great length, all of which is incredibly positive and simply proves what we instinctively know. Electronic cigarettes, vapourisers, vapour products or whatever you want to call them (just not nic-sticks please) are not encouraging the rabid youth of today to start smoking combustible tobacco, at least not in the current regulatory climate at any rate. Who knows, that may all change.

At least in the good ol’ US of A things remain consistently, uh, ludicrous. According to a recently released study, and I’m going to use that term incredibly loosely for this one, ‘cos let’s face it, do we really need a study to tell us that teens experiment? No of course not, experimentation is a key aspect of growing up, yet many public health nannies like to think that experimentation is in fact devil spawn. So what makes this study so “important”?

Exposure to nicotine in electronic cigarettes (e-cigarettes) is becoming increasingly common among adolescents who report never having smoked combustible tobacco.

So once again beating that evil Nick O’Teen drum, but why focus solely on vapourisers? Because it is the hot contentious topic that allows junk science to get funding of course. The aim of this “important study”; to evaluate whether e-cigarette use among 14-year-old adolescents who have never tried combustible tobacco is associated with risk of initiating use of 3 combustible tobacco products. In short, they are looking to see if vapourisers are indeed a gateway to smoking.

Sadly, this “ideal” is not going to go away anytime soon, and as the regulatory landscape changes it will inevitably be revisited again, and again, and again. Because, well kids.

Let’s have a look at the design of the study as it is very telling. Forty public schools in Los Angeles metro area were approached to participate in this study and chosen (apparently) because of their diverse demographic characteristics and proximity.  Only ten schools decided to actually participate, which of course narrows the statistical field substantially. It was of course a self-completion survey with follow-ups at intervals of 6 months, starting in Fall of 2013 (during 9th grade), first follow-up in Spring 2014 and finally Fall 2014 (10th grade).  All in all, pretty routine stuff.  What is striking though is the socio-demographic breakdown.  Out of the 2530 participants, almost half were hispanic (44.2%), with a majority of the parents being college graduates (33.7%). Certainly an interesting demographic they have.

In some societal cultures, smoking is more prevalent than in others, this could be down to a number of factors such as stereotyping a particular ethnicity as being “worse off” than another, sadly this does happen.

At each interval, the participants were asked about their vapouriser and combustible tobacco product use, based on the “Youth Behaviour Risk Surveillance” and “Monitoring the Future” surveys which are detailed for combustible tobacco, but vapourisers are in there as an after-thought.

The answers available for these questions ran along the lines of, “lifetime use”, “past 6-month use” (both of which required a yes or no answer) with the “lifetime=yes” answer used as a basis for the primary exposure variable. In other words, if the participant answered “yes” to either, they were marked down as a current user and subsequently removed from the study results.

Out of 4100 eligible students, 226 didn’t provide consent to take part, 478 didn’t receive parental consent, out of which 439 consent was declined by the parent and 39 didn’t return the consent form or the parent was unreachable. Leaving a total of 3396 to be enrolled into the study. A further 70 were excluded due to incomplete information leaving 3,326.

If the participant had answered “yes” to lifetime or past 6-month use, as in classified as “having already smoked” they were excluded. 768 were excluded from 3,326 leaving a grand total of 2,558 never smokers to take part in the initial survey to provide a baseline. Six months later only 2,473 completed the first follow-up with a further 92 at the final follow-up which should leave a total of 2,381. Instead, once again there is some statistical fudgery going on and 2,530 were included in the final analysis because they had completed the 6 month or final follow-up.

But you want to know what they actually found, that’s why you’re reading this.


Taken directly from the study, they “positively” associated vapouriser “ever use” with the baseline for ever use of a combustible tobacco product, that is if the participant had ever used a combustible tobacco product then it was associated with ever use of an e-cigarette. They also state that there were positive associations of e-cigarette use among male, native Hawaiian/Pacific Islander ethnicity with parents that have a “lower education level”. Talk about fine tuning! So if you’re male, native Hawaiian with college level parents you’re more likely to experiment with a vapouriser, or so science would tell us. Not to mention that they don’t differentiate between “ever use” and “sustained use”; as in the the study failed to document that any of these kids actually used e-cigarettes regularly.

The researchers don’t mind a little logical leap here or there when they go on to state:

In the sample of students who were never smokers of combustible tobacco products at baseline, baseline e-cigarette ever users were more likely to report past 6-month use of any combustible tobacco product at the 6-month follow-up

So those kids that never smoked tobacco, but decided to experiment with vapourisers were more likely to try another product. Go figure! Give those researchers a gold star for stating the blindingly obvious. What is startling is the fact that it’s pretty clear in Table 2 only 617 (about 9% of the total) “ever users” of vapourisers (out of the “combined sample” of 3326), a total of 196 may decide to try a cigarette based on the answers to some leading questions:

  • Would you try smoking a cigarette if one of your best friends offered it to you?
  • Do you think you would smoke in the next six months?
  • Are you curious about smoking?

With one of the following answers rated accordingly:

  1. Probably not
  2. Probably yes
  3. Definitely yes

Of course, they also asked about “expected outcomes” to smoking which they assessed using an average of two responses “I think I might enjoy” and “I think I might feel bad” scored using a three point scale. 1; disagree, 2; agree, 3; and strongly agree. Already I can clearly see a weighted pattern here where the study is designed to encourage the participants to answer positively, those that don’t are discarded.

Follow Up



So what does this tell us? Unlike the previous table which only looked at those “enrolled” once the participants that failed to fully provide information, and existing “ever smokers” had been excluded, this one looks at those that passed that stage and completed either of the two follow-ups. Interestingly, the authors chose to exclude the 768 that had already tried cigarettes but left the 222 that had already tried vapourisers in. This is a clear indication of selection bias, but then again the authors were only looking at whether or not vapourisers could be a gateway to smoking, not the other way around. I suspect the overall outcome would be significantly different had the 768 existing “ever smoker” teens had been included in the final results, but then there wouldn’t be much of a story to tell would there?

At the first follow-up, out of the 222 “ever use” of vapourisers, 21 had tried a combustible cigarette, 37 had tried cigars and 38 had tried hookah, but out of the 222 ever use had not tried other tobacco products. %69.3 had stuck with vapourisers. Whilst in the “never use” of e-cigarettes column, 68 had tried cigarettes, 70 had tried cigars and 122 had tried hookah. True the sample size is much larger, but even so %3 of never smoker, never e-cig use had tried combustible tobacco.

There’s a similar pattern at 12 months:

Ever use of e-cigarettes, 17 tried cigarettes, 33 tried cigars and 25 tried hookah with 160 staying with vaping. 54 had tried one or more tobacco products (24%)

Never use of e-cigarettes (never smokers), 74 tried cigarettes, 93 tried cigars and 127 tried hookah. 210 had tried one or more tobacco products. (9.4%) – these are the kids that have never smoked.

It does beg the question why the 768 participants who had declared either “lifetime” or “past 6-month” use were excluded, but you only need to look at some of the headlines that this study, and it’s associated press release have generated to figure out why.

In the supplemental document the authors try to clarify a few points related to the baseline sample.

  • Never smokers, who reported no past 6-month use of any tobacco product at both follow-ups, of course get put into the “non-users” bracket. Out of the total, 2,007 were classified as such (83.4%).
  • “Experimenters” were defined as past 6-month use of any combustible product (not including vapourisers) at the first follow-up but not at the 12-month. This equalled 139 participants (5.8%).
  • “Later initiators” were defined as any use of combustibles (past 6-month) at the final follow-up but not at the 6-month follow-up; 161 users (6.7%)
  • “Sustained users” defined as reporting past 6-month use of combustible products at both follow-ups. 99 users (4.1%)

It even states in the supplement:

A polytomous generalized linear mixed model (GLMM) using a generalized logit function including school and baseline ever e-cigarette use as fixed effects with ‘non-users’ as the reference category showed that baseline ever (vs. never) e-cigarette users were more likely to be ‘experimenters’

Which is pretty much saying that teens experiment. Let’s face it, if a teen is vaping odds are they’ll try a cigarette find it horrible and go back to vaping, which is pretty much what this data shows us, but you’d never guess that from the headlines would you?

Linda Bauld, puts this quite clearly in her post on the Conversation:

But were these young people more likely to then try smoking (either cigarettes, cigars or hookah pipes)? The researchers found that those who said they’d tried an e-cigarette at the start of the study were also more likely to have tried smoking six months later (30.7% vs 8.1%) and 12 months later (25.2% vs 9.3%).

There are several caveats. As the authors make clear, this association doesn’t prove that e-cigarettes cause young people to take up smoking – it merely demonstrates a statistical link between the two. On top of this, the way e-cigarette and tobacco use were measured was very basic, only determining whether people had “ever” or “recently” used them, not whether this was regular or sustained use.

In other words, at 6 months into vaping (let us assume that the user started vaping at the time of the study) they wanted to try cigarettes, but 12 months later only 9.3% of the 222 would do that. Strange isn’t it, that a study focusses on one aspect (the ever dreaded “gateway”) but the numbers don’t give a true representation, after all the authors only really analysed 222 sets of answers.

If I were to mark this study paper, I’d give it a big fat “T” with the comment, must try harder.