Considerations related to vaping as a possible gateway into cigarette smoking: an analytical review

Abstract

Background: Toxicant levels are much lower in e-cigarettes than cigarettes. Therefore, introducing e-cigarettes into the market seems likely to reduce smoking-related diseases (SRD). However, vaping might provide a gateway into cigarette smoking for those who otherwise would never have smoked, a concern fuelled by cohort studies showing vaping predicts subsequent smoking initiation in young people. Methods: In this discussion paper, we consider various aspects of the gateway issue in youths. We provide a descriptive critical review of results from prospective studies relating to the gateway effect and the extent to which the studies considered other potential confounding variables associated with smoking initiation. We then estimate the effects of omitting a confounding variable, or misclassifying it, on the association between vaping and subsequent smoking initiation, and determine how the prevalence of smoking might be affected by any true gateway effects of vaping. Finally, we examine trends in e-cigarette and smoking prevalence in youths based on national surveys. Results: First, we demonstrate that although studies report that vaping significantly predicts smoking initiation following adjustment for various other predictors, the sets of predictors considered are quite incomplete. Furthermore, no study considered residual confounding arising from inaccurate measurement of predictors. More precise adjustment may substantially reduce the association. Second, we show any true gateway effect would likely affect smoking prevalence only modestly. Third, we show smoking prevalence in U.S. and U.K. youths in 2014–2016 declined somewhat faster than predicted by the preceding trend; a substantial gateway effect suggests the opposite. Finally, we argue that even if some gateway effect exists, introducing e-cigarettes still likely reduces SRDs. Conclusions: Given that the existence of any true gateway effect in youth is not yet clearly demonstrated the population health impact of introducing e-cigarettes is still likely to be beneficial.

An investigation of factors encouraging and deterring EC use: a thematic analysis of accounts from UK adults

“…The speed of nicotine delivery was important to users and one participant chose a specific device because of this: Paul (ex-smoker) [111][112][113][114]: […] I buy Juul […] and one of the things that makes it really stand out is that it has a substance called nicotine salt which is this new form of liquid that enters your bloodstream quicker and gives you more of a nicotine hit […] Some participants felt that ECs had increased their nicotine dependency: : […] I know that's wrong now especially because of how much I'm using my e-cigarette at the moment, but I'm always saying I don't actually need it, I don't want it, but if it's there I'll have it […] Beth, who had never previously smoked, discussed how she now believes she is addicted to nicotine: : […] the option whether they wanted to try it with nicotine or without so I think initially I tried one of my friends but I got one of the ones without [nicotine] for myself and I tried my friends and hers had nicotine in and I noticed the difference, like getting the head rush […] I guess probably I am addicted because I wouldn't choose to use a non-nicotine one […] This raises the issue of ECs providing a gateway to cigarette smoking. EC use acting as a gateway to smoking is commonly raised as a concern for adolescents (Chatterjee et al, 2018;Lee et al, 2019), but this suggests that the gateway potential should be explored further with adults.…”

Population-level counterfactual trend modelling to examine the relationship between smoking prevalence and e-cigarette use among US adults

“…Concerning the gateway, longitudinal studies have reported significant associations between e-cigarette use among non-smoking adolescents and subsequent smoking initiation [3]. However, Lee et al [4] and Chan et al [5] have argued that this effect is not causal, but rather due to common liabilities, that is, shared risk factors for both vaping and smoking, such as parental smoking and delinquent behavior, which predispose adolescents to both forms of nicotine use and which are not adequately controlled in such analyses [6][7][8]. Conversely, it has been hypothesized that e-cigarette use among non-smoking adolescents may prevent those who otherwise would have smoked cigarettes from doing so, as their e-cigarette use may replace cigarette smoking, rather than lead to cigarette smoking.…”