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On the dual use of electronic cigarettes and conventional cigarettes

I've noticed Stanton Glantz makes much of the fact some vapers are 'dual users'  - I have no idea what proportion of vapers are dual users, but I do want to try to nip something in the bud....

Dual use is claimed to be problematic for two reasons. Firstly, because it represents a 'failure' to have someone quit entirely - that is to say that a dual user might be using e-cigs where or when they can't smoke, and still smoking when they are able. The fact that e-cigs offer a way to avoid smoking prohibition is held to be a lost opportunity for the forcing of smokers off nicotine entirely. This claim has previously been rubbished by Carl Phillips here and elsewhere on the antiTHRlies site.

The second claim is one that I've seen Glantz write up in his objections to the comments submitted by Reynolds in the FDA's consultation. He wrote that there is evidence that using smokeless tobacco and tobacco at the same time has some kind of synchronous effect that actually enhances the danger of each. This needs to be challenged, because it's the type of claim that could easily be picked up and become common currency. I've looked at the paper in question (it's the INTERHEART study), and spotted the error he's made - an error which would make a 1st year psychology undergrad blush.

The INTERHEART study monitored smoking/smokeless tobacco habits and the increase  in heart disease. It was a massive worldwide, longitudinal study, and is a very impressive piece of work. To present the findings, they calculated the odds ratio (OR) of having a heart attack (acute myocardial infarction -AMI) for each tobacco related behavior. An OR of, say 2.5, is a multiplier of 2.5  times the liklihood to suffer a heart attack in the period than a never smoker.

With respect to dual use, the study found that smokers who also chew tobacco have an OR of 4.09 for having an AMI. The average OR for all smokers was found to be 2.95. On this basic reading it would, therefore, appear to be the case that dual users are more likely to suffer a heart attack. However, without knowing more about the sample (and we don't - the detail is not included in the survey), we cannot compare like with like.

Take, the raw data on smoking. We have the average OR of 2.95, but every cigarette smoked per day increases the OR of having an AMI by 1.056. So, someone smoking 40+ per day has a 9.16 OR compared with someone smoking 1-2 per day where the increase is an approximate 1.25 OR. An OR of 4.09 corresponds to smokers consuming around 20 cigarettes per day.

So, what is more likely? That there is some kind of as yet not understood multiplier effect of dual usage, meaning that an average smoker can expect to have their risk upped by a factor of 1.39?  Or that the sample of dual users in the survey was actually made up of people who smoked more to begin with, or had recently cut down by using smokeless tobacco, but not long enough for the pre-existing risk to have gone down?

I know which one I find more believable, but again there's really no way of telling until more is known about the dual-user sample. It's clear, though, that citing the statistics as a 'warning' about dual use is a classic piece of cherrypicking, designed only to cause fear and uncertainty. This sentence, from the submission to the FDA is, therefore, a patent untruth: "This new information means that, if anything, the Mejia et al. model underestimates the negative health impact of promoting smokeless tobacco as a harm reduction strategy"

Indeed: "This new information means that, if anything, more research needs to be done, and most likely will find that dual use is associated with less tobacco smoking and a consequential reduction in AMI over time" is an equally valid reading of the same study, but it is just as tendentious and I would never submit it as a statement of fact. And nor would any serious academic.

Addendum: We (ECF) are about to launch a survey into vaping habits - one that we hope will be the largest and most comprehensive of its kind. We should gain a good insight into exactly what people's vaping habits are.

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