Vaping Nicotine Is Far Less Harmful Than Smoking Tobacco

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whether cognitive impairment was reversed. The
advantage of both these approaches would be to
minimize reverse causality and known and unknown
confounding. In our opinion, this is the best way to
clarify the causal nature of the association between
impaired lung function and dementia and, if this is the
case, potentially shed light on the underlying mechanism.
Tom C. Russ, PhD, MRCPsych
Edinburgh, United Kingdom
Mika Kivimäki, FMedSci
G. David Batty, PhD, DSc
London, United Kingdom
AFFILIATIONS: Alzheimer Scotland Dementia Research Centre (Drs
Russ and Batty); Edinburgh Dementia Prevention and the Division of
Psychiatry, Centre for Clinical Brain Sciences (Dr Russ), University
of Edinburgh; and the Department of Epidemiology and Public
Health (Drs Kivimäki and Batty), University College.
FINANCIAL/NONFINANCIAL DISCLOSURES: See earlier cited article
for author conflicts of interest.
CORRESPONDENCE TO: Tom C. Russ, PhD, MRCPsych,
Alzheimer Scotland Dementia Research Centre, University of
Edinburgh, 7 George Square, Edinburgh, EH8 9JZ, United
Kingdom; e-mail: T.C.Russ@ed.ac.uk
Copyright Ó2020 American College of Chest Physicians. Published
by Elsevier Inc. All rights reserved.
DOI: https://doi.org/10.1016/j.chest.2020.04.037
References
1. Russ TC, Kivimäki M, Batty GD. Respiratory disease and lower
pulmonary function as risk factors for dementia: a systematic review
with meta-analysis. Chest. 2020;157(6):1538-1558.
2. Munafo M, Davey-Smith G. Repeating experiments is not enough.
Nature. 2018;553:399-400.
3. Shrine N, Guyatt AL, Erzurumluoglu AM, et al. New genetic signals
for lung function highlight pathways and chronic obstructive
pulmonary disease associations across multiple ancestries. Nat Genet.
2019;51(3):481-493.
Vaping Nicotine Is Far Less
Harmful Than Smoking
Tobacco
To the Editor:
In a previous issue of CHEST (May 2020), Bozier et al
1
reviewed the recent research on the potential health
effects of e-cigarettes. We would like to comment on
several of the claims made in the article.
The most relevant question for smokers is whether vaping
nicotine is less harmful than smoking the cigarettes it is
designed to replace. The evidence suggests it is far less
harmful. The National Academies of Sciences,
Engineering, and Medicine report
2
found substantial
evidence that “exposure to potentially toxic substances
from e-cigarettes is significantly lower compared with
combustible tobacco cigarettes”and “reduced short-term
adverse health outcomes in several organ systems.”
2
The authors quite rightly conclude that “e-cigarette use
is not risk-free for non-smokers.”However,
international studies of adults and youth show that
current use of e-cigarettes by never smokers is rare, and
regular use is very rare, usually <0.5%.
Most of the research on the harms of e-cigarettes is from
in vitro and animal studies. How these findings translate
to health effects in humans is uncertain, when many
human studies show substantial health improvements in
smokers who switch to vaping.
The recent outbreak of lung injuries in the United States
electronic-cigarette, or vaping, product use-associated
lung injury (EVALI)
3
was not due to nicotine vaping.
Most, if not all, cases were the result of vaping black-
market tetrahydrocannabinol contaminated with
vitamin E acetate.
4
No cases have been associated with
commercial nicotine vaping.
The authors claim that we cannot exclude the possibility
that “e-cigarettes pose a similar, lesser, or greater cancer
risk than cigarette smoking”because of the presence of
carcinogens and potential adverse effects in two studies.
Given the greatly reduced number of carcinogens and
their lower concentration in e-cigarette vapor, it is very
likely that the cancer risk from vaping is only a tiny
fraction of the risk from smoking.
4
Finally, the authors appear to misunderstand the role of
tobacco harm reduction in questioning the value of
vaping as a quitting aid when many ex-smokers
continue to vape after quitting. Replacing a high-risk
behavior with a far less harmful one is a well-accepted
public health strategy, for example, methadone
maintenance for heroin addiction.
Evidence from randomized controlled trials, population
studies, and better-quality observational studies shows
that e-cigarettes are effective quitting aids.
5
The authors
are correct that short-term nicotine replacement therapy
is less harmful than vaping, but it is also far less effective
for quitting, and very few smokers use it.
Colin Paul Mendelsohn, MB BS (Hons)
Double Bay, NSW, Australia
Wayne Hall, PhD
Saint Lucia, QLD, Australia
chestjournal.org 835

AFFILIATIONS: From the University of New South Wales Ringgold
standard institution - School of Public Health and Community
Medicine (Dr Mendelsohn); and the University of Queensland (Dr
Hall), Saint Lucia Campus Ringgold standard institution, Centre for
Youth Substance Abuse Research.
FINANCIAL/NONFINANCIAL DISCLOSURES: The authors have
reported to CHEST the following: C. P. M. has received funding from
Pfizer Australia, Johnson & Johnson Pacific and Perrigo Australia for
teaching, consulting, and conference expenses. C. P. M. has never
received any funding or payments from e-cigarette or tobacco
companies; serves as a Board member of the Australian Tobacco
Harm Reduction Association (ATHRA), a health promotion charity.
ATHRA has received donations in the past from Australian vape
shops. This formally ceased in March 2019. None declared (M. H.).
CORRESPONDENCE TO: Colin Mendelsohn, MB BS (Hons),
University of New South Wales Ringgold standard institution, School
of Public Health and Community Medicine, 11 Carlotta Rd, Double
Bay, NSW, 2028, Australia; e-mail: mendel@bigpond.net.au
Copyright Ó2020 American College of Chest Physicians. Published
by Elsevier Inc. All rights reserved.
DOI: https://doi.org/10.1016/j.chest.2020.02.077
References
1. Bozier J, Chivers EK, Chapman DG, et al. The evolving landscape
of e-cigarettes: a systematic review of recent evidence. Chest.
2020;157(5):1362-1390.
2. National Academies of Sciences, Engineering and Medicine. Public
Health Consequences of e-Cigarettes. Washington, DC: The National
Academies Press; 2018.
3. Blount BC, Karwowski MP, Shields PG, et al. Vitamin E acetate in
bronchoalveolar-lavage fluid associated with EVALI. N Engl J Med.
2020;382(8):697-705.
4. Stephens WE. Comparing the cancer potencies of emissions from
vapourised nicotine products including e-cigarettes with those of
tobacco smoke [published online ahead of print August 4, 2017]. Tob
Control. http://doi.10.1136/tobaccocontrol-2017-053808.
5. Mendelsohn C, Hall W, Borland R. Could vaping help lower smoking
rates in Australia? Drug Alcohol Rev. 2020;39(4):415-418.
Response
To the Editor:
We thank Drs Mendelsohn and Hall for their response
to our systematic review of current literature
surrounding the (potential) health effects of
e-cigarettes.
1
We acknowledge their commitment to
improving health outcomes for tobacco cigarette
smokers and welcome their opinion in the current
debate. While supporting our conclusion that “smokers
who switch to e-cigarettes may experience harm
reduction,”they disagree with our cautious approach by
not endorsing e-cigarettes as a harm reduction strategy.
Harm reduction is founded on the understanding that
complete abstinence is an unrealistic goal. This is likely
untrue for most smokers, with recent data from the
National Health Interview Survey and Cancer Control
Supplement reporting that 80% of older adults who had
ever smoked had successfully quit.
2
Nonetheless, if we
consider those tobacco smokers who are unable to
successfully quit despite the use of tobacco cessation
counseling and pharmacotherapy, one must assess the
harm reduction efficacy of e-cigarettes. In arguing that
“e-cigarettes are effective quitting aids,”Drs Mendelsohn
and Hall draw on two randomized controlled trials of
e-cigarettes as a smoking cessation tool. Hajek et al
3
reported one-year smoking abstinence rates of 18% in
those using e-cigarettes vs 9.9% in the nicotine
replacement therapy (NRT) group. Recently, Walker
et al
4
reported 6-month smoking abstinence rates of
7% with e-cigarettes plus nicotine patches vs 2% with
nicotine patches alone. Thus, e-cigarettes may be more
effective at promoting smoking abstinence than NRT,
but the effect is rather modest. When also considering
that e-cigarette use may increase the risk of smoking
relapse
5
and promote smoking initiation,
5
we are left
questioning the public health benefit of e-cigarettes. We
acknowledge that from an individual perspective,
e-cigarettes may be an appropriate harm reduction
strategy. However, this would require identification of
the subset of smokers in whom e-cigarettes are
efficacious for smoking cessation. At present, such a
phenotype is unknown.
Drs Mendelsohn and Hall acknowledge that e-cigarettes
are not without risk. It is therefore important to ask
whether long-term e-cigarette use sufficiently lowers risk
to translate to improvements in long-term health
outcomes. The evidence of little harm reduction after
reduction of tobacco smoking without complete
abstinence
6,7
makes this question particularly pertinent.
The limited evidence in humans reveals short-term
improvements in respiratory health for tobacco smokers
who transition to e-cigarettes.
8
However, emerging
preclinical evidence suggests that long-term use may
increase the risk for lung cancer and pre-cancerous
bladder lesions.
9
However, whether the toxicant burden
associated with lifetime e-cigarette use, on top of previous
tobacco smoking history, does or does not contribute to
life-time risk of respiratory disease, cardiovascular
disease, cancer, and mortality is unknown.
The goal of our review was to systematically summarize
the recent literature, regardless of the findings, on the
possible health effects of e-cigarette use. We hope that in
doing so it has provided much-needed clarity as to the
current evidence and will be an impetus for future
research and regulation.
David G. Chapman, PhD
Sydney, NSW, Australia
Alexander N. Larcombe, PhD
Perth, WA, Australia
836 Correspondence [158#2 CHEST AUGUST 2020 ]