November 8, 2016

vaping and smoking

A research letter published in JAMA has examined the association between e-cigarette use and progression to smoking in a group of adolescents in the US. Roundup comments accompanied this analysis.

Title, Date of Publication & Journal

Association of e-Cigarette Vaping and Progression to Heavier Patterns of Cigarette Smoking

Study’s main claims – and are they supported by the data

The paper does not prove the claim that e-cigarette vaping causes progression to heavier patterns of cigarette smoking.

The authors’ final conclusion – that transition from vaping to cigarette smoking may warrant particular attention in tobacco control policy – avoids making explicit causal connections between vaping and cigarette smoking. However, the authors do not explicitly acknowledge the fact that we cannot conclude that vaping leads to cigarette smoking. These data do not allow us to rule out alternative (non-causal) explanations for this relationship.

These data demonstrate a clear association between vaping and subsequent cigarette smoking. However, we cannot rule out the possibility that those adolescents who have tried vaping at baseline may be those who will also experiment with cigarette smoking.

An adolescent’s propensity to smoke cigarettes is incredibly hard to quantify. The authors do make great efforts to quantify this characteristics (e.g. by asking if they feel they might enjoy smoking, or are curious about it – as detailed in the references). When these factors were accounted for in the analysis, the observed associations between vaping and subsequent smoking were substantially reduced. It is certainly possible that better measurement of the adolescents’ propensity to smoke, and therefore better control of this characteristic, would lead to further reduction in the apparent association between vaping and smoking.

Strengths/Limitations

Strengths:

Strengths of the study include the prospective collection of data, and the longitudinal design – data was collected twice over a period of 6 months for the same adolescents.

The sample size is fairly large, including just over 3,000 adolescents, although the number of smokers or vapers among this group was low.

The analysis included a high proportion, 3084 (90%) out of 3396, of the students who provided assent and consent to enrol in the study.

Limitations:

Use of e-cigarettes and cigarette smoking was measured by self-report.

The data contained very small number of vapers and smokers. Therefore the “frequent” vapers were those who had vaped at least 3 times in the past month, and “prior” vapers are those who have ever used an e-cigarette, even only a single time.

It would be better to see analyses for baseline non-smokers only, since the analyses shown indicate that the associations between vaping and subsequent smoking are different depending on baseline smoking behaviour. However, the small number of smokers at baseline means that this is unlikely to impact on the study’s conclusions.

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