February 7, 2017

expert reaction to study on teen vaping and future smoking

Published in Tobacco Control new research claims vaping can lead to tobacco smoking in teenagers.

Prof. Peter Hajek, Director of the Tobacco Dependence Research Unit at Queen Mary University of London (QMUL), said:

“This paper just shows that teenagers who try cigarettes are more likely to also try e-cigarettes (and the other way round) compared to teenagers who do not do such things. This is trivial. People who read sci-fi novels are also more likely to watch sci-fi movies than people who do not like sci-fi. There is no reason why these activities should be performed in one order only.

“The findings provide no justification for the grossly misleading ‘one-way bridge’ headline. There is actually hard evidence that this is false and that the effects of vaping experimentation on smoking is more likely to be the opposite, i.e. smoking reduction. The increased experimentation with vaping by adolescents has been accompanied by a continuing or even accelerating decrease in youth smoking.”

Prof. Linda Bauld, Professor of Health Policy at the University of Stirling, said:

“This article is the latest American study to claim that using an e-cigarette can lead to tobacco smoking in teenagers – in fact the authors go as far as to describe it as a ‘one way bridge’ to smoking. If this were true it would be very worrying. We know e-cigarettes are far less harmful than smoking and we also know that teenagers are experimenting with these products. While we don’t want to encourage that, the key public health priority is to prevent young people from starting to smoke, a habit that eventually kills one in two regular smokers. If trying an e-cigarette causes regular smoking, then we should be alarmed. However, this study and previous American studies which have made similar assertions have not found this, and so we must be very cautious about jumping to such a conclusion on the basis of this study.

“The article used data from the Monitoring the Future study¹, a repeat cross sectional survey of American high school students that has been in place for many years – in fact it started in 1975. It asks a series of questions on tobacco use and in 2014 added questions about e-cigarettes, with use assessed by a measure of any vaping in the past 30 days.

“What did the study involve? It took a subsample from the over 13,000 12^th graders (17-18 year olds) in the MTF survey from 2014 and followed up 347 of them one year later (on average at age 19) in 2015. Questions were asked about ever and past 30 day (recent) smoking and past 30 day vaping in 2014. The follow up analysis focused on any smoking in the past 12 months in 2015 amongst those who had never smoked in 2014 but had either vaped or not vaped in the past 30 days in 2014. Questions were also asked about cigarettes posing ‘a great risk’ of harm at baseline and follow up.

“What did the study find? Among the teenagers who had never smoked, those who had used an e-cigarette at least once in the past 30 days in 2014 were more than four times more likely to have tried a tobacco cigarette at least once by 2015. These same teenagers who had recently vaped in 2014 but never smoked were also more than 4 times more likely to have ‘moved away’ from believing that tobacco cigarettes posed a great risk of harm to health.

“What did the authors conclude? That having tried an e-cigarette in 2014 independently predicted having tried a tobacco cigarette one year later, that vaping may have made these young people think smoking wasn’t so bad after all, and that this change in perception might be the reason why they then tried a tobacco cigarette. They argue that this provides a solid scientific basis for policies to strongly regulate vaping (even e-cigarettes that don’t contain nicotine) as it can lead to tobacco smoking.

“There are many questions that need to be asked about these conclusions. The first is that the measures of both vaping and smoking are weak and could include simple experimentation – there is no measure of either regular vaping or smoking, and in fact the smoking measure at follow up included those who had tried a cigarette even once. There is nothing to suggest that these young people have become regular smokers and therefore could suffer the health harms that smoking causes. The second is that the change in risk perception between baseline and follow up could have been influenced by many things not measured in the survey. The third, which the authors acknowledge, is that there are lots of factors which influence whether someone starts smoking. Some of the most important (susceptibility to smoking, and whether friends and family smoke) were simply not assessed in this study.

“Yet arguably the most significant problem with this article is that it is completely silent about the context in which the study took place. In short, there is key information from Monitoring the Future that appears nowhere in the text.

“The missing information is that cigarette smoking amongst teenagers in the USA has steadily declined since the late 1990s. As measured in the MTF survey, past 30 day smoking peaked at 28.3% in 1996 and fell to 5.9% by 2016. In fact since 2011 when e-cigarette use began to rapidly rise in the USA, there has been a particularly marked decline in teen cigarette smoking, from 11.7% to 5.9%. Declines have also been observed in all other forms of tobacco use from when the MTF survey started measuring them (i.e. smokeless tobacco, cigars) to 2016¹. The real headline is that teen smoking in the USA is at an all-time low, including during the period when e-cigarette experimentation was rising. If e-cigarettes were causing tobacco smoking, these trends would be reversed. But they have not reversed. 

“The very small sample of 12^th graders included in this particular study may well have tried e-cigarettes first and then tried smoking. Yet, overall, Monitoring the Future provides no evidence to suggest that vaping is acting as a gateway, or indeed a ‘one way bridge’ to smoking at the population level. To assert that is simply a bridge too far.”

¹Johnson, L et al (2016) Monitoring the Future: National Survey Results on Drug Use, 1975-2016: 2016 Overview, http://www.monitoringthefuture.org//pubs/monographs/mtf-overview2016.pdf

* ‘E-cigarette use as a predictor of cigarette smoking: results from a 1-year follow-up of a national sample of 12th grade students’ by Richard Miech et al. published in Tobacco Control on Tuesday 7 February.

Declared interests

Prof. Linda Bauld: None to declare

Prof. Peter Hajek: “I have no links with any e-cigarette manufacturers. My research into e-cigarette safety and effects has been funded by NIHR, PHE, UKCTAS and MHRA.”