E-cigarettes and the obsolescence of combustion

KEYWORDS:

• Tobacco use disorder
• electronic nicotine delivery devices
• electronic cigarette
• e-cigarette
• nicotine
• smoking

Disruptive technologies change almost every aspect of our lives, and this also applies to nicotine and tobacco use. Electronic cigarettes became available 12 years ago and several other technologies that vaporize tobacco or nicotine have appeared more recently. Tobacco companies are developing new strategies that include product diversification, massive investments (billions, not millions) in new vaporizing technologies, and a stated goal to reduce the harm caused by smoking and to eliminate tobacco combustion [1].

The harm caused by tobacco comes overwhelmingly from its combustion, and every other mode of tobacco use is less dangerous than combustible products. Some regulatory authorities are willing to implement harm reduction policies and to accommodate new technologies that compete with tobacco combustion [2]. For example, the US FDA recently announced a new strategy consisting of progressively eliminating nicotine from cigarettes, while allowing smokers to switch to less hazardous tobacco or nicotine products [3]. Similarly, the UK Stop Smoking Services recently included e-cigarettes in their assistance to smokers, and in 2017 e-cigarettes were included for the first time in the national ‘Stoptober’ smoking cessation campaign. In contrast, the World Health Organization (WHO) and the WHO Secretariat of the Framework Convention for Tobacco Control have rejected harm reduction strategies and new vaporization technologies, and advocate an abstinence-only approach using traditional strategies such as tax increases, advertising bans, media campaigns, smoke-free laws, age limits, etc.

Among scientists the debate is fierce. Proponents and opponents disagree on the amount of harm reduction, gateway effects, effects on smoking cessation, dual use, duration of addiction, effects at population level, regulation and policies, and information made available to the public. This debate is highly emotional and fraught with bias, ideology and preconceptions on both sides. Against this background, it is important to be aware that emotions can cloud rationality, to reflect on one’s own biases, and to make a balanced and neutral assessment of the situation based on evidence.

1. Degree of harm reduction

Tobacco combustion produces hundreds of substances that are known to be toxic. These substances are either absent, or are present in markedly lower amounts, in the aerosols produced by e-cigarettes and novel technologies that heat but do not burn tobacco. Nonetheless, such devices are not harmless, and long-term use may cause harm that has not been detected in the mainly short-term studies that have been performed to date. It may take years to ascertain the long-term effects of vaping, but there is already some evidence that switching from cigarettes to vaping improves clinical outcomes in smokers [4]. The important point is that non-combustible products are less dangerous than combustible products [5–8], although the risks of e-cigarettes should not be downplayed [9,10].

A precautionary principle should be applied, which implies that a risk evaluation should be performed, assessing the consequences of adopting new technologies and the consequences of rejecting them. The precautionary principle does not imply that new technologies should be blocked until full information is available, but it implies that regulations should be proportional and should not discriminate against innovative products in favor of status quo.

2. Gateway effects

Several longitudinal observational studies found an increase in the risk of subsequent smoking in young nonsmokers who vaped compared with non-vapers [8,11]. However, the recent report of the US National Academies of Sciences, Engineering and Medicine (NASEM) concluded that in never smokers e-cigarettes may lead to ever smoking, but found no evidence that e-cigarette use leads to regular smoking [8]. And the 2018 update of the Public Health England (PHE) report on e-cigarettes concluded that in nonsmokers a causal link has not been established between vaping and smoking initiation or progression to regular smoking [12]. The report also asserted that the common liability theory is a plausible explanation for the association between vaping and smoking (i.e. both are determined by the same risk factors) [12].

All studies of gateway effects are based on observational (i.e. nonexperimental) studies, but it is difficult to establish the causality of associations found in observational studies because of confounding effects. Even after statistical adjustments, residual confounding and spurious effects may still account for much of the observed associations [13,14]. Several observational studies were limited by their use of questionable definitions of vaping and smoking, and many were not designed specifically to examine gateway effects but used preexisting survey data. Consequently, their adjustment for confounders is often quite incomplete.

The impact of the gateway effect at population level depends on two factors: the relative risk of subsequent regular smoking among never smokers and the prevalence of vaping among never smokers. Fortunately, e-cigarette use among never smokers is rare even in the UK, a country where vaping is common [15]. Gateway effects can also be documented by studies of the impact of bans on e-cigarette sales to minors on the subsequent incidence of smoking in this group, but studies to date on this topic have produced conflicting results [16–18].

Many of the criteria that should be considered before deciding whether an association is causal have either not been met or are not documented in the case of the claim that e-cigarettes can lead to regular cigarette smoking [13]. Because of the impossibility of conducting experiments in young non-users, gateway theories may never be provable and may always remain controversial in this field as in other fields (e.g. cannabis use and subsequent heroin use) [13].

3. Effects on smoking cessation

A recent Cochrane meta-analysis of studies of e-cigarettes and smoking cessation concluded that e-cigarettes may help smokers to stop smoking, but the effect was modest: 9% of users of nicotine-containing e-cigarettes stopped smoking after 6 months versus 4% of those who used a placebo e-cigarette that delivered vapor and flavors but no nicotine [19]. However, this conclusion was based on only two randomized trials, in which participants used first generation e-cigarettes (‘cig-alike’) that deliver much less nicotine and vapor than recent models; moreover, these two studies did not test the effects of the non-nicotine elements of e-cigarettes (gestures, inhalation of visible vapor, flavors). The NASEM report also concluded that there is ‘limited evidence’ that e-cigarettes may be effective aids to promote smoking cessation [8]. The PHE report presents evidence from various data sources (not just randomized trials) suggesting that e-cigarettes may have an effect on smoking cessation [12]. It is regrettable that, 12 years after e-cigarettes became available in Europe and North America, only two randomized trials were eligible for inclusion in the Cochrane meta-analysis [19]. However, several randomized trials are ongoing and should soon provide a reliable answer to the question of e-cigarettes and smoking cessation.

In contrast with the Cochrane Review and the NASEM and PHE reports, three meta-analyses of observational studies found that e-cigarettes decreased the odds of quitting smoking [20–22]. However, the Cochrane group follows strict, pre-established criteria for study selection (only randomized trials), outcome criteria (only cessation at longest follow up) and counting of participants lost at follow-up (they are counted as smokers), whereas the three meta-analyses also included cohort and cross-sectional studies, used whatever duration of follow up was reported in the original papers, and did not systematically count participants lost at follow up as smokers [20–22]. This is a much weaker approach. Causality cannot be assessed in cross-sectional studies, and observational studies are subject to residual confounding after adjustment. In addition, observational studies of current e-cigarette users evidently exclude subjects who have successfully quit smoking with e-cigarettes before baseline. Therefore, such studies include only participants who have failed to quit smoking with e-cigarettes. As such, by design some of the studies that are included in the three meta-analyses artificially produce negative results.

4. Dual use

Most e-cigarette users continue to smoke cigarettes (‘dual users’) but there is good evidence that vaping enables smokers to substantially reduce the number of cigarettes they smoke [23], although an opposite effect has also been reported [24]. Nicotine-aided smoking reduction is a predictor of smoking cessation [25]. Unfortunately, there are currently too few longitudinal studies of dual users to understand the impact of dual use on nicotine dependence, smoking cessation and health in the long term [8]. There is a continuum of dual usage and only those who substantially reduce their smoking may derive some benefit. In any case, smoking reduction has value mainly if it increases the odds of subsequent quitting, because only stopping smoking – not reducing cigarette consumption – will substantially decrease mortality.

5. Population effects

Given the prevalence of smoking in the population (15–30% in most Western countries), the probable efficacy of e-cigarettes for smoking cessation, and the probably small effects of e-cigarettes on initiation of regular smoking in never smokers, the overall impact of e-cigarettes on smoking prevalence in the population and on smoking-related mortality are likely to be positive [8,26]. However, these positive effects may be modest, even in the UK, a country where e-cigarettes are more widely used than elsewhere [27,28], and some scenarios foresee negative effects in the long term (50 years hence) [8]. Furthermore, uptake of vaping by smokers has been slow, and many vapers have stopped vaping and returned to smoking. The total population effects will remain small as long as policies, public information, marketing campaigns and technological improvements do not result in higher rates of e-cigarette use among smokers.

Of course, conventional tobacco control measures (taxes, smoking bans, media campaigns, etc.) remain vital, but such measures will take decades to drive smoking rates down to minimal levels. Replacement of tobacco combustion by new technologies, combined with conventional tobacco control measures, will undoubtedly produce better results than policies that reject new technologies. Opponents fear that adopting new technologies may delay or threaten the implementation of conventional measures, but it is quite possible that – in fact – new technologies can help to implement anti-cigarette measures by increasing public perception that cigarettes are obsolete, defective, outmoded, unacceptable products for which there are safer alternatives.

6. Public information

Surveys conducted in several countries have found that substantial proportions of the population wrongly believe that e-cigarettes are as dangerous as combustible cigarettes, and that the prevalence of this false belief increases over time [15,29]. Unfavorable press coverage, negative campaigns by e-cigarette opponents, and lack of training of health professionals may explain this situation. Progress in this area will be slow if the information relayed to the public, opinion leaders, health professionals, and policy makers is not scientifically valid. All these audiences have a right to be honestly informed.

7. Perspectives

New technologies and the tobacco industry’s industrial strategies (including product diversification, massive investment in vaporizing technologies and related marketing), combined with harm reduction policies, may result in the partial replacement of combustible tobacco products by a range of vaporization technologies, with ensuing decreases in smoking-related harm. However, it is not certain that this scenario will occur. Such an outcome can only be achieved if appropriate public policies and industrial strategies are combined to maximize uptake of new technologies by smokers while minimizing any associated risks at the population level. Without joined-up efforts to eliminate combustible tobacco products, the prediction that one billion tobacco-related deaths will occur in the 21st century may well materialize.

Declaration of interest

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This manuscript has not been funded.