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BACKGROUND Electronic cigarettes (ECs) are handheld electronic vaping devices which produce an aerosol by heating an e-liquid. 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 safety, tolerability and effectiveness of using electronic cigarettes (ECs) to help people who smoke tobacco achieve long-term smoking abstinence, in comparison to non-nicotine EC, other smoking cessation treatments and no treatment. SEARCH METHODS We searched the Cochrane Tobacco Addiction Group’s Specialized Register to 1 February 2023, and Cochrane Central Register of Controlled Trials (Central), Medline, Embase, and PsycINFO to 1 July 2023, and reference-checked and contacted study authors. SELECTION CRITERIA We included 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 as these studies have the potential to provide further information on harms and longer-term use. Studies had to report an eligible outcome. DATA COLLECTION AND ANALYSIS We followed standard Cochrane methods for screening and data extraction. Critical outcomes were abstinence from smoking after at least six months, adverse events (AEs), and serious adverse events (SAEs). 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 pairwise and network meta-analyses (NMA). MAIN RESULTS We included 88 completed studies (10 new to this update), representing 27,235 participants, of which 47 were randomized controlled trials (RCTs). Of the included studies, we rated ten (all but one contributing to our main comparisons) at low risk of bias overall, 58 at high risk overall (including all non-randomized studies), and the remainder at unclear risk. There is high certainty that nicotine EC increases quit rates compared to nicotine replacement therapy (NRT). In absolute terms, this might translate to an additional four quitters per 100. There is moderate-certainty evidence that the rate of occurrence of AEs is similar between groups. SAEs were rare, and there is insufficient evidence to determine whether rates differ between groups due to very serious imprecision. There is moderate-certainty evidence, limited by imprecision, that nicotine EC increases quit rates compared to non-nicotine EC. In absolute terms, this might lead to an additional three quitters per 100. There is moderate-certainty evidence of no difference in the rate of AEs between these groups. There is insufficient evidence to determine whether rates of SAEs differ between groups, due to very serious imprecision. Due to issues with risk of bias, there is low-certainty evidence that, compared to behavioral support only/no support, quit rates may be higher for participants randomized to nicotine EC. In absolute terms, this represents an additional four quitters per 100. There was some evidence that (non-serious) AEs may be more common in people randomized to nicotine EC and, again, insufficient evidence to determine whether rates of SAEs differed between groups. Results from the NMA were consistent with those from pairwise meta-analyses for all critical outcomes, and there was no indication of inconsistency within the networks. Data from non-randomized studies were consistent with RCT data. The unwanted effects (at medium and short term) reported most often with nicotine EC were throat or mouth irritation, headache, cough and feeling sick. These appeared similar to those people experience when using NRT. These effects were reduced over time as people continued using nicotine EC. 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 due to risk of bias inherent in the study design. 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 the 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. Further RCTs are underway. To ensure the review continues to provide up-todate 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.

Original publication

DOI

10.19256/d.cadmos.06.2024.05

Type

Journal article

Journal

Dental Cadmos

Publication Date

01/01/2024

Volume

92

Pages

466 - 479