The health pros and cons of e-cigarettes – Evidence ambivalence

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The jury is still out on the potential dangers and benefits of e-cigarettes, though there seems to be more bad than good news around. The American Journal of Public Health looks at the growing research base relating to vaping, while the Pulmonology Advisor says consumer use has sparked widespread negative consequences but also some success in smoking cessation.

The research is a meta-analysis of studies into e-cigarette use and smoking cessation. It finds that as consumer products, in observational studies, e-cigarettes were not associated with increased smoking cessation in the adult population – but in randomised trials, providing free e-cigarettes as a therapeutic intervention was associated with increased smoking cessation. There are summaries of the research and articles below.

Meanwhile, in the 5 February 2021 report for Pulmonology Advisor, Tori Rodriguez described contrasting research and interviewed professors at the University of California and McGill University in Canada to ascertain the public health implications of their research.


E-cigarettes for smoking cessation: The continued debate

When electronic cigarettes were introduced to the market, many consumers and experts were hopeful that the products could reduce harms associated with combustible cigarette smoking and ultimately aid in smoking cessation, writes Rodriguez.

Manufacturers promoted these points as benefits associated with e-cigarettes even while the debate continued about their relative harms.

Based on the available evidence, it has become clear that consumer e-cigarette use has led to widespread negative consequences, such as reversing some of the gains in public health efforts against smoking and increasing rates of nicotine consumption as well as eventual cigarette smoking among adolescents.

However, some experts note that e-cigarette use may still have a role in smoking cessation when used in a clinical context, and two recent studies explored this topic, continues writes Rodriguez in Pulmonology Advisor.

In a randomised clinical trial (RCT) published in November 2020 in JAMA, Professor Mark J Eisenberg at McGill University and colleagues examined the effects of nicotine e-cigarettes combined with individual counselling for smoking cessation.

The trial was initially slated to run for 52 weeks, but a delay in e-cigarette manufacturing necessitated early termination of the trial and reduced enrolment from the target of 486 participants to 376 participants (mean age, 52 years; 47% women) from 17 sites in Canada.

Participants were randomly assigned to receive nicotine e-cigarettes (n=128), non-nicotine e-cigarettes (n=127), or no e-cigarettes (n=121) for a 12-week period, and all received individual counselling.

At 12 weeks, point prevalence abstinence (the primary endpoint) was significantly greater in the nicotine e-cigarette plus counselling group compared to counselling. At 24 weeks, however, the difference between groups was no longer significant, Pulmonology Advisor continues.

While no significant difference was observed between the non-nicotine e-cigarettes plus counselling group and the counselling only group at 12, the point prevalence abstinence between groups was significantly greater at 24. The majority of participants in all groups experienced adverse events, most commonly cough and dry mouth.

In a meta-analysis published in February 2021 in the American Journal of Public Health, Dr Richard Wang, an assistant professor in the School of Medicine at the University of California – San Francisco – and colleagues explored the link between e-cigarette use and smoking cessation based on 55 observational studies and nine RCTs.

In analyses of observational studies, they found that e-cigarette use on a consumer basis was not associated with smoking cessation among adult smokers in general or smokers motivated to quit smoking. However, higher rates of cessation were observed in RCTs comparing the effects of e-cigarettes provided to participants for study purposes vs conventional therapy.

Based on these findings, the authors concluded that e-cigarettes “should not be approved as consumer products but may warrant consideration as a prescription therapy.”

The experts speak

To glean various perspectives on the potential utility and harm of using e-cigarettes for smoking cessation, Pulmonology Advisor interviewed Eisenberg and Wang, as well as Dr Scott S Oh, associate professor of medicine at the David Geffen School of Medicine at the University of California – Los Angeles.

What does the evidence suggest thus far regarding whether e-cigarettes are helpful or harmful in smoking cessation?

Eisenberg: Nicotine e-cigarettes appear to be moderately efficacious for smoking cessation and safe when used for a short duration.

Oh: There is limited mixed data on whether e-cigarettes are helpful to those trying to stop smoking.

For example, there are studies that show those who use e-cigarettes have less craving for regular cigarettes, less symptoms of nicotine withdrawal, and higher rates of quitting. However, other studies have shown that e-cigarette use made no difference.

Given the mixed results, it is important not to forget about more established options which have been shown to be helpful in helping people stop smoking, such as group counselling and medications.

Also, it is important to remember we do not yet know the potential long-term effects of e-cigarette use, including the potential for lung damage and cancer. In addition to uncertainty about long-term dangers, there is the possibility of e-cigarette associated acute lung injury or EVALI, which has been associated with nicotine-containing cartridges which were in some cases illicitly obtained.

The potential danger to children should also be considered. E-cigarette cartridges should be kept away from children to prevent accidental nicotine overdose which may be fatal. The danger of second-hand e-cigarette exposure is unknown but is suspected to be less harmful than exposure to traditional second-hand smoke.

What do your recent findings add to our understanding of this topic?

Eisenberg: Among adults motivated to quit smoking, nicotine e-cigarettes compared to counselling alone significantly increased point prevalence abstinence at 12 weeks, but the difference was no longer significant at 24 weeks.

Reduction in mean self-reported daily cigarette consumption from baseline was significantly greater among participants randomised to nicotine and non-nicotine e-cigarettes compared with counselling alone at 12 weeks and 24 weeks.

Wang: Our work shows that e-cigarettes as consumer products – which is the only way they are available – do not help people quit smoking and may make it harder to quit. Our analysis is based on the largest evidence base to date, and we used observational studies to assess the effect of e-cigarettes on smoking cessation in the real world.

We also found that the smaller number of randomised controlled trials that assess the value of giving smokers free e-cigarettes as part of a medically supervised smoking cessation programme suggests that, in a clinical context, e-cigarettes might be effective.

To use e-cigarettes as a medicine, however, they would have to be approved by the US Food and Drug Administration(FDA) as medicines and, as far as we know, no e-cigarette company has applied to have e-cigarettes approved as a medicine.

What are recommendations for clinicians about how to advise patients?

Eisenberg: When first-line smoking cessation therapies, such as nicotine replacement therapies (eg patches and gum) and pharmaceutical therapies (eg varenicline and bupropion) have not worked, nicotine e-cigarettes should be considered as a second- or third-line therapy for smoking cessation.

Though e-cigarettes are generally considered less harmful than conventional cigarettes, patients should use e-cigarettes for the shortest period of time, as their long-term safety is still unknown.

Wang: Clinicians should caution patients who choose to use e-cigarettes or who ask about using e-cigarettes that the risks of e-cigarette use are not fully understood. Clinicians should offer smoking cessation counselling to all patients who smoke and prescribe FDA-approved therapies for those patients who are interested in using them.

Oh: Clinicians cannot make strong recommendations about e-cigarettes given the lack of convincing data for smoking cessation. However, some common sense guidelines have been issued about e-cigarettes: e-cigarettes should not be used recreationally, especially by non-smokers; and for smokers, e-cigarette use is likely to be less harmful, especially if used short-term to help stop smoking both traditional and e-cigarettes.

But it is important to remember that the long-term effects are not yet known.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry.


Growing evidence base relating to e-cigarettes – American Journal of Public Health

The February 2021 issue of the American Journal of Public Health features research and a special section on the growing evidence base about electronic nicotine dispensing systems or ENDS – both their hazards and potential utility in reducing tobacco dependence – reported the American Public Health Association.

The following are thumbnails of the research and articles:


Article summary

E-Cigarette Use and Adult Cigarette Smoking Cessation: A meta-analysis


Richard J Want, Sudhamavi Bhadriraju and Stanton A Glantz

Author affiliations: University of California – San Francisco, and the Kaiser Permanente Medical Center in California.

Published in the American Journal of Public Health, edition of February 2021



To determine the association between e-cigarette use and smoking cessation.


We searched PubMed, Web of Science Core Collection, and EMBASE and computed the association of e-cigarette use with quitting cigarettes using random effects meta-analyses.


We identified 64 papers (55 observational studies and 9 randomized clinical trials [RCTs]).

In observational studies of all adult smokers (odds ratio [OR] = 0.947; 95% confidence interval [CI] = 0.772, 1.160) and smokers motivated to quit smoking (OR = 0.851; 95% CI = 0.684, 1.057), e-cigarette consumer product use was not associated with quitting.

Daily e-cigarette use was associated with more quitting (OR = 1.529; 95% CI = 1.158, 2.019) and less-than-daily use was associated with less quitting (OR = 0.514; 95% CI = 0.402, 0.665).

The RCTs that compared quitting among smokers who were provided e-cigarettes to smokers with conventional therapy found e-cigarette use was associated with more quitting (relative risk = 1.555; 95% CI = 1.173, 2.061).


As consumer products, in observational studies, e-cigarettes were not associated with increased smoking cessation in the adult population. In RCTs, provision of free e-cigarettes as a therapeutic intervention was associated with increased smoking cessation.

Public health implications

E-cigarettes should not be approved as consumer products but may warrant consideration as a prescription therapy.


Article summary

Should E-Cigarette Regulation be Based on Randomised Trials or Observational Studies?

Evan Mayo-Wilson

Author affiliation: Department of Epidemiology and Biostatistics, Indiana University School of Public Health – Bloomington, United States.

Published in the American Journal of Public Health, edition of February 2021


Synthesising the results of randomised clinical trials (RCTs)using meta-analysis, Wang et al found that providing free e-cigarettes probably helps some people quit smoking. This is consistent with a recent Cochrane review finding that free e-cigarettes provided in trials were more effective than nicotine replacement for smoking cessation and possibly more effective than behavioural therapy.

Both reviews highlight important clinical differences across individual trials, and both reviews show that e-cigarettes have small absolute benefits because most people are unsuccessful in their attempts to quit smoking tobacco. Moreover, both reviews point to concerning evidence that people use e-cigarettes longer than other smoking cessation aids.

In the long-term, switching to e-cigarettes might be better than continuing to smoke tobacco; however, these trials do not show whether the short-term benefits of e-cigarettes offset their long-term harms when compared with nicotine replacement, such as gums or lozenges, which are effective for smoking cessation and used for a shorter time.

Wang et al argue that if regulators had approached e-cigarettes as they approach drugs and medical devices, RCTs restricted to people who are motivated to quit smoking would have been appropriate for assessing their potential benefits. Although their effects on smoking cessation are small, e-cigarettes might even compare favourably with other smoking cessation therapies such as bupropion, varenicline, and nicotine inhalers.


Article summary

Is Good Enough Good Enough? E-cigarettes, evidence and policy

Amy Lauren Fairchild

Author affiliation: College of Public Health at Ohio State University, United States

Published in the American Journal of Public Health, edition of February 2021


In 2017, the US Food and Drug Administration (FDA) opened the door to considering e-cigarettes as a harm-reduction product. In January 2020, the agency signalled its intention to continue to chart that path, writing:

“[T]he potential for [electronic nicotine delivery systems] to act as a substitute for cigarettes, thereby encouraging smokers to seek to switch completely away from combustible cigarettes, may be dependent, in part, upon the product having acceptability and abuse liability more comparable to a cigarette.”

Yet what has always remained unclear is what evidentiary standard the FDA will apply as it reviews products and evaluates public health benefit.


Article summary

E-cigarettes: A public health threat, not a population health intervention

Rebekah E Gee, William R Boles and Dean G Smith

Author affiliations: Louisiana State University, United States

Published in the American Journal of Public Health, edition of February 2021

Introductory remarks

Cigarette smoking is the single most deadly personal behaviour in human history and remains a potent population health threat. Today in the United States, one in five deaths can be attributed to cigarette smoking.

Over decades, billions of dollars have been invested in smoking cessation efforts and clinicians, policymakers and public health professionals have fought to limit future tobacco use through a variety of mechanisms.

Within a few years, e-cigarettes have imperilled these efforts and created unprecedented opportunities for a new generation of youths to become addicted to nicotine and tobacco products.

Concluding remarks

Public health professionals should focus messaging and communications strategies on where the public health data lead us. Population health data indicate, and the meta-analysis by Wang et al supports, that e-cigarettes are not a viable tool to combat tobacco smoking as a mass market consumable.

Public health professionals should discourage their use, and these products should be tightly regulated. Any recommendation of e-cigarette use should be relegated to clinicians as a targeted clinical intervention for smoking cessation.

Preventing initiation of smoking of both combustible tobacco products and e-cigarettes and increasing successful cessation must continue to be top public health priorities.


Article summary

Reporting Certainty of Evidence on E-Cigarette Use for Adult Smoking Cessation

Sean Grant

Author affiliation: Richard M Fairbanks School of Public Health at Indiana University in Indianapolis, United States

Published in the American Journal of Public Health, edition of February 2021

Introductory remarks

Endorsed by more than 100 organisations internationally, Grading of Recommendations Assessment, Development and Evaluation (GRADE) provides an explicit, systematic and transparent approach to the assessment of quality of evidence (or ‘certainty of evidence’). It is designed for evaluating the certainty of evidence from randomised clinical trials (RCTs) on therapeutic interventions to inform clinical decision making as well as observational studies on exposures to inform public health decision making.

Consequently, GRADE can be used to assess certainty of evidence in the two distinct bodies of evidence that Wang et al discuss in their article on e-cigarette use for adult smoking cessation: RCTs of e-cigarettes as a prescription therapy and observational studies of e-cigarettes as consumer products.


Pulmonology Advisor article (Open access) – E-Cigarettes for Smoking Cessation: The continued debate


American Journal of Public Health article (Open access) – E-Cigarette Use and Adult Cigarette Smoking Cessation: A Meta-Analysis


American Journal of Public Health article (Open access) – Should E-Cigarette Regulation Be Based on Randomized Trials or Observational Studies?


American Journal of Public Health article(Open access) – Is Good Enough Good Enough? E-Cigarettes, Evidence, and Policy


American Journal of Public Health article (Open access) – E-Cigarettes: A Public Health Threat, Not a Population Health Intervention


American Journal of Public Health article (Open access) – Reporting Certainty of Evidence on E-Cigarette Use for Adult Smoking Cessation




Australian GPs willing to prescribe e-cigarettes to help patients quit


JAMA editorial: Research strengthens case for e-cigarettes for smoking cessation


Oxford review: E-cigarettes versus traditional nicotine replacement therapies



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