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Review
. 2016 Sep 14;9(9):CD010216.
doi: 10.1002/14651858.CD010216.pub3.

Electronic cigarettes for smoking cessation

Jamie Hartmann-Boyce  1 , Hayden McRobbie, Chris Bullen, Rachna Begh, Lindsay F Stead, Peter Hajek
Affiliations
Review

Electronic cigarettes for smoking cessation

Jamie Hartmann-Boyce et al. Cochrane Database Syst Rev. .

Update in

Abstract

Background: Electronic cigarettes (ECs) are electronic devices that heat a liquid into an aerosol for inhalation. The liquid usually comprises propylene glycol and glycerol, with or without nicotine and flavours, and stored in disposable or refillable cartridges or a reservoir. Since ECs appeared on the market in 2006 there has been a steady growth in sales. Smokers report using ECs to reduce risks of smoking, but some healthcare organizations, tobacco control advocacy groups and policy makers have been reluctant to encourage smokers to switch to ECs, citing lack of evidence of efficacy and safety. Smokers, healthcare providers and regulators are interested to know if these devices can help smokers quit and if they are safe to use for this purpose. This review is an update of a review first published in 2014.

Objectives: To evaluate the safety and effect of using ECs to help people who smoke 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 for relevant records from 2004 to January 2016, together with reference checking and contact with study authors.

Selection criteria: We included randomized controlled trials (RCTs) in which current smokers (motivated or unmotivated to quit) were randomized to EC or a control condition, and which measured abstinence rates at six months or longer. As the field of EC research is new, we also included cohort follow-up studies with at least six months follow-up. We included randomized cross-over trials, RCTs and cohort follow-up studies that included at least one week of EC use for assessment of adverse events (AEs).

Data collection and analysis: We followed standard Cochrane methods for screening and data extraction. Our main outcome measure was abstinence from smoking after at least six months follow-up, and we used the most rigorous definition available (continuous, biochemically validated, longest follow-up). We used a fixed-effect Mantel-Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for each study, and where appropriate we pooled data from these studies in meta-analyses.

Main results: Our searches identified over 1700 records, from which we include 24 completed studies (three RCTs, two of which were eligible for our cessation meta-analysis, and 21 cohort studies). Eleven of these studies are new for this version of the review. We identified 27 ongoing studies. Two RCTs compared EC with placebo (non-nicotine) EC, with a combined sample size of 662 participants. One trial included minimal telephone support and one recruited smokers not intending to quit, and both used early EC models with low nicotine content and poor battery life. We judged the RCTs to be at low risk of bias, but under the GRADE system we rated the overall quality of the evidence for our outcomes as 'low' or 'very low', because of imprecision due to the small number of trials. A 'low' grade means that further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. A 'very low' grade means we are very uncertain about the estimate. Participants using an EC were more likely to have abstained from smoking for at least six months compared with participants using placebo EC (RR 2.29, 95% CI 1.05 to 4.96; placebo 4% versus EC 9%; 2 studies; 662 participants. GRADE: low). The one study that compared EC to nicotine patch found no significant difference in six-month abstinence rates, but the confidence intervals do not rule out a clinically important difference (RR 1.26, 95% CI 0.68 to 2.34; 584 participants. GRADE: very low).Of the included studies, none reported serious adverse events considered related to EC use. The most frequently reported AEs were mouth and throat irritation, most commonly dissipating over time. One RCT provided data on the proportion of participants experiencing any adverse events. The proportion of participants in the study arms experiencing adverse events was similar (ECs vs placebo EC: RR 0.97, 95% CI 0.71 to 1.34 (298 participants); ECs vs patch: RR 0.99, 95% CI 0.81 to 1.22 (456 participants)). The second RCT reported no statistically significant difference in the frequency of AEs at three- or 12-month follow-up between the EC and placebo EC groups, and showed that in all groups the frequency of AEs (with the exception of throat irritation) decreased significantly over time.

Authors' conclusions: There is evidence from two trials that ECs help smokers to stop smoking in the long term compared with placebo ECs. However, the small number of trials, low event rates and wide confidence intervals around the estimates mean that our confidence in the result is rated 'low' by GRADE standards. The lack of difference between the effect of ECs compared with nicotine patches found in one trial is uncertain for similar reasons. None of the included studies (short- to mid-term, up to two years) detected serious adverse events considered possibly related to EC use. The most commonly reported adverse effects were irritation of the mouth and throat. The long-term safety of ECs is unknown. In this update, we found a further 15 ongoing RCTs which appear eligible for this review.

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Conflict of interest statement

Within the last three years HM has received honoraria for speaking at research symposia and received benefits in kind and travel support from, and has provided consultancy to, the manufacturers of smoking cessation medications.

Within the last three years PH has provided consultancy for and received research funding from GSK, Pfizer, Novartis and other manufacturers of smoking cessation medications.

Two authors (HM, CB) have additional declarations: CB and HM were investigators on a study of ECs from an EC manufacturer (Ruyan Group, Beijing and Hong Kong). Ruyan supplied the ECs used in the trial and contracted with Health NZ Ltd. to undertake the study. Health New Zealand Ltd funded The University of Auckland to conduct the trial, independently of Ruyan Group (Holdings) Ltd. The trial design conduct, analysis and interpretation of results were conducted independently of the sponsors. CB and HM were investigators on the ASCEND EC trial funded by the Health Research Council of New Zealand that used product supplied at no charge from PGM international, a retailer of ECs.

JHB, RB and LS have no conflicts of interest to declare.

Figures

Figure 1
Figure 1
Study flow diagram for review update 2016
Figure 2
Figure 2
Study flow diagram for original review, 2014
Figure 3
Figure 3
Risk of bias summary: review authors' judgements about each risk of bias item for each included study.
Analysis 1.1
Analysis 1.1
Comparison 1 Smoking cessation, Outcome 1 Nicotine EC versus placebo EC.
Analysis 1.2
Analysis 1.2
Comparison 1 Smoking cessation, Outcome 2 Nicotine EC versus nicotine replacement therapy.
Analysis 2.1
Analysis 2.1
Comparison 2 Adverse Events, Outcome 1 Proportion of participants reporting adverse events: Nicotine EC versus placebo EC.
Analysis 2.2
Analysis 2.2
Comparison 2 Adverse Events, Outcome 2 Proportion of participants reporting adverse events: nicotine EC versus nicotine replacement therapy.
See this image and copyright information in PMC

References

References to studies included in this review

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References to studies excluded from this review

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References to ongoing studies

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    1. ACTRN12612001210864. An open‐label randomised pragmatic policy trial examining effectiveness of short‐term use of Nicotine Replacement Therapy (NRT) vs short‐ or long‐term use of NRT vs short‐ or long‐term use of NRT or electronic nicotine delivery systems for smoking cessation in cigarette smokers. ACTRN12612001210864 (accessed 15 August 2016).
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    1. ISRCTN60477608. The efficacy of e‐cigarettes compared with nicotine replacement therapy, when used within the UK stop smoking service. ISRCTN60477608 2014 (accessed 15 August 2016).
    1. KCT0001277. Effect of an electronic cigarette for smoking reduction and cessation in Korean male smokers: a randomized, controlled study. KCT0001277 2014 (accessed 15 August 2016). - PubMed
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Additional references

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References to other published versions of this review

    1. McRobbie H, Bullen C, Hajek P. Electronic cigarettes for smoking cessation and reduction. Cochrane Database of Systematic Reviews 2012, Issue 11. [DOI: 10.1002/14651858.CD010216] - DOI - PubMed
    1. McRobbie H, Bullen C, Hartmann‐Boyce J, Hajek P. Electronic cigarettes for smoking cessation and reduction. Cochrane Database of Systematic Reviews 2014, Issue 12. [DOI: 10.1002/14651858.CD010216.pub2] - DOI - PubMed

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