Electronic Cigarettes for Smoking Cessation.
Thursday, January 5, 2023
Posted by: Natalia Gromov
Hartmann-Boyce J, Lindson
N, Butler AR, et al.
Electronic Cigarettes for
Smoking Cessation.
Cochrane Database Syst Rev. 2022;11(11):CD010216. Published 2022 Nov 17.
doi:10.1002/14651858.CD010216.pub7
Background. Electronic
cigarettes (ECs) are handheld electronic vaping devices which produce an
aerosol by heating an e-liquid. Some people who smoke use ECs to stop or reduce
smoking, although some organizations, advocacy groups and policymakers have
discouraged this, citing lack of evidence of efficacy and safety. People who
smoke, healthcare providers and regulators want to know if ECs can help people
quit smoking, and if they are safe to use for this purpose. This is a review
update conducted as part of a living systematic review.
Objectives. To
examine the effectiveness, tolerability, and safety of using electronic
cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking
abstinence.
Search methods. We
searched the Cochrane Tobacco Addiction Group's Specialized Register, the
Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, and
PsycINFO to 1 July 2022, and reference-checked and contacted study authors.
SELECTION CRITERIA: We included randomized controlled trials (RCTs) and
randomized cross-over trials, in which people who smoke were randomized to an
EC or control condition. We also included uncontrolled intervention studies in
which all participants received an EC intervention. Studies had to report
abstinence from cigarettes at six months or longer or data on safety markers at
one week or longer, or both.
Data collection and
analysis. We followed standard Cochrane methods for
screening and data extraction. Our primary outcome measures were abstinence
from smoking after at least six months follow-up, adverse events (AEs), and
serious adverse events (SAEs). Secondary outcomes included the proportion of people
still using study product (EC or pharmacotherapy) at six or more months after
randomization or starting EC use, changes in carbon monoxide (CO), blood
pressure (BP), heart rate, arterial oxygen saturation, lung function, and
levels of carcinogens or toxicants, or both. We used a fixed-effect
Mantel-Haenszel model to calculate risk ratios (RRs) with a 95% confidence
interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated
mean differences. Where appropriate, we pooled data in meta-analyses.
Main results. We
included 78 completed studies, representing 22,052 participants, of which 40
were RCTs. Seventeen of the 78 included studies were new to this review update.
Of the included studies, we rated ten (all but one contributing to our main
comparisons) at low risk of bias overall, 50 at high risk overall (including
all non-randomized studies), and the remainder at unclear risk. There was high
certainty that quit rates were higher in people randomized to nicotine EC than
in those randomized to nicotine replacement therapy (NRT) (RR 1.63, 95% CI 1.30
to 2.04; I<sup>2</sup> = 10%; 6 studies, 2378 participants). In
absolute terms, this might translate to an additional four quitters per 100
(95% CI 2 to 6). There was moderate-certainty evidence (limited by imprecision)
that the rate of occurrence of AEs was similar between groups (RR 1.02, 95% CI
0.88 to 1.19; I<sup>2</sup> = 0%; 4 studies, 1702 participants).
SAEs were rare, but there was insufficient evidence to determine whether rates
differed between groups due to very serious imprecision (RR 1.12, 95% CI 0.82
to 1.52; I<sup>2</sup> = 34%; 5 studies, 2411 participants). There
was moderate-certainty evidence, limited by imprecision, that quit rates were
higher in people randomized to nicotine EC than to non-nicotine EC (RR 1.94,
95% CI 1.21 to 3.13; I<sup>2</sup> = 0%; 5 studies, 1447
participants). In absolute terms, this might lead to an additional seven
quitters per 100 (95% CI 2 to 16). There was moderate-certainty evidence of no
difference in the rate of AEs between these groups (RR 1.01, 95% CI 0.91 to
1.11; I<sup>2</sup> = 0%; 5 studies, 1840 participants). There was
insufficient evidence to determine whether rates of SAEs differed between
groups, due to very serious imprecision (RR 1.00, 95% CI 0.56 to 1.79;
I<sup>2</sup> = 0%; 8 studies, 1272 participants). Compared to
behavioural support only/no support, quit rates were higher for participants
randomized to nicotine EC (RR 2.66, 95% CI 1.52 to 4.65; I<sup>2</sup>
= 0%; 7 studies, 3126 participants). In absolute terms, this represents an
additional two quitters per 100 (95% CI 1 to 3). However, this finding was of
very low certainty, due to issues with imprecision and risk of bias. There was
some evidence that (non-serious) AEs were more common in people randomized to
nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I<sup>2</sup> = 41%, low
certainty; 4 studies, 765 participants) and, again, insufficient evidence to
determine whether rates of SAEs differed between groups (RR 1.03, 95% CI 0.54 to
1.97; I<sup>2</sup> = 38%; 9 studies, 1993 participants). Data from
non-randomized studies were consistent with RCT data. The most commonly
reported AEs were throat/mouth irritation, headache, cough, and nausea, which
tended to dissipate with continued EC use. Very few studies reported data on
other outcomes or comparisons, hence evidence for these is limited, with CIs
often encompassing clinically significant harm and benefit.
Authors'
conclusions. There is high-certainty evidence that ECs
with nicotine increase quit rates compared to NRT and moderate-certainty
evidence that they increase quit rates compared to ECs without nicotine.
Evidence comparing nicotine EC with usual care/no treatment also suggests
benefit, but is less certain. More studies are needed to confirm the effect
size. Confidence intervals were for the most part wide for data on AEs, SAEs
and other safety markers, with no difference in AEs between nicotine and
non-nicotine ECs nor between nicotine ECs and NRT. Overall incidence of SAEs was
low across all study arms. We did not detect evidence of serious harm from
nicotine EC, but longest follow-up was two years and the number of studies was
small. The main limitation of the evidence base remains imprecision due to the
small number of RCTs, often with low event rates, but further RCTs are
underway. To ensure the review continues to provide up-to-date information to
decision-makers, this review is a living systematic review. We run searches
monthly, with the review updated when relevant new evidence becomes available.
Please refer to the Cochrane Database of Systematic Reviews for the review's
current status.
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