AVA SYNOPSIS
A newly published review in the Cochrane Library Database of Systematic Reviews provides further evidence that e-cigarettes and vapor products are more effective than nicotine replacement therapy (NRT) in helping smokers quit.
The authors employed 50 completed studies that had been published up to January 2020, which represented over 12,400 participants. Of the 50 studies, 26 were randomized control trials, “in which people who smoke were randomized to an [e-cigarette] or control condition.” In order to be included in the Cochrane review, “studies had to report abstinence from cigarettes at six months or longer and/or data on adverse events or other markers of safety at one week or longer.”
This is the latest Cochrane review update and includes 35 new studies. The authors found that there was “moderate-certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine [e-cigarettes] than in those randomized to nicotine replacement therapy.” The authors found that e-cigarette use translated “to an additional four successful quitters per 100.” The authors also found higher quit rates in participants that had used e-cigarettes containing nicotine, compared to the participants that had not used nicotine.
The authors noted the most reported adverse events were “throat/mouth irritation, headache, cough, and nausea, which tended to dissipate over time with continued use.”
The authors conclude that more “people probably stop smoking for at least six months using e-cigarettes than using nicotine replacement therapy,” and e-cigarettes may be useful to smokers without behavior support. Further, the authors found that for “every 100 people using nicotine e-cigarettes to stop smoking, 10 might successfully stop, compared with only six of 100 people using nicotine replacement therapy or nicotine-free e-cigarettes.”
The results are similar to a 2016 Cochrane review of e-cigarettes for smoking cessation, which found that there was “evidence from two trials that [e-cigarettes] help smokers to stop smoking in the long term compared to placebo [e-cigarettes].” Cochrane reviews are recognized worldwide as representing a gold standard for systematic reviews.
Implications: E-cigarettes and vaping tools have emerged as an effective tool in helping smokers quit. Despite this, many elected officials have moved to ban their sale in localities and states, with these officials often claiming that e-cigarettes are not needed because FDA-approved quitting tools exist. This study provides further evidence that e-cigarettes have helped many American adults quit smoking and are, indeed, more effective than FDA-approved nicotine replacement therapy in helping smokers quit.
ABSTRACT
Objectives: To evaluate the effect and safety of using electronic cigarettes (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 to January 2020, together with reference‐checking and contact with 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. To be included, studies had to report abstinence from cigarettes at six months or longer and/or data on adverse events (AEs) or other markers of safety at one week or longer.
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, AEs, and serious adverse events (SAEs). Secondary outcomes included changes in carbon monoxide, blood pressure, heart rate, blood oxygen saturation, lung function, and levels of known carcinogens/toxicants. We used a fixed‐effect Mantel‐Haenszel model to calculate the risk ratio (RR) with a 95% confidence interval (CI) for dichotomous outcomes. For continuous outcomes, we calculated mean differences. Where appropriate, we pooled data from these studies in meta‐analyses.
Main results: We include 50 completed studies, representing 12,430 participants, of which 26 are RCTs. Thirty‐five of the 50 included studies are new to this review update. Of the included studies, we rated four (all which contribute to our main comparisons) at low risk of bias overall, 37 at high risk overall (including the 24 non‐randomized studies), and the remainder at unclear risk.
There was moderate‐certainty evidence, limited by imprecision, that quit rates were higher in people randomized to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (risk ratio (RR) 1.69, 95% confidence interval (CI) 1.25 to 2.27; I2 = 0%; 3 studies, 1498 participants). In absolute terms, this might translate to an additional four successful quitters per 100 (95% CI 2 to 8). There was low‐certainty evidence (limited by very serious imprecision) of no difference in the rate of adverse events (AEs) (RR 0.98, 95% CI 0.80 to 1.19; I2 = 0%; 2 studies, 485 participants). SAEs occurred rarely, with no evidence that their frequency differed between nicotine EC and NRT, but very serious imprecision led to low certainty in this finding (RR 1.37, 95% CI 0.77 to 2.41: I2 = n/a; 2 studies, 727 participants).
There was moderate‐certainty evidence, again limited by imprecision, that quit rates were higher in people randomized to nicotine EC than to non‐nicotine EC (RR 1.71, 95% CI 1.00 to 2.92; I2 = 0%; 3 studies, 802 participants). In absolute terms, this might again lead to an additional four successful quitters per 100 (95% CI 0 to 12). These trials used EC with relatively low nicotine delivery. There was low‐certainty evidence, limited by very serious imprecision, that there was no difference in the rate of AEs between these groups (RR 1.00, 95% CI 0.73 to 1.36; I2 = 0%; 2 studies, 346 participants). There was insufficient evidence to determine whether rates of SAEs differed between groups, due to very serious imprecision (RR 0.25, 95% CI 0.03 to 2.19; I2 = n/a; 4 studies, 494 participants).
Compared to behavioural support only/no support, quit rates were higher for participants randomized to nicotine EC (RR 2.50, 95% CI 1.24 to 5.04; I2 = 0%; 4 studies, 2312 participants). In absolute terms this represents an increase of six per 100 (95% CI 1 to 14). However, this finding was very low‐certainty, due to issues with imprecision and risk of bias. There was no evidence that the rate of SAEs varied, but some evidence that non‐serious AEs were more common in people randomized to nicotine EC (AEs: RR 1.17, 95% CI 1.04 to 1.31; I2 = 28%; 3 studies, 516 participants; SAEs: RR 1.33, 95% CI 0.25 to 6.96; I2 = 17%; 5 studies, 842 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 over time with continued use. Very few studies reported data on other outcomes or comparisons and hence evidence for these is limited, with confidence intervals often encompassing clinically significant harm and benefit.
Authors’ conclusions: There is moderate‐certainty evidence that ECs with nicotine increase quit rates compared to ECs without nicotine and compared to NRT. Evidence comparing nicotine EC with usual care/no treatment also suggests benefit, but is less certain. More studies are needed to confirm the degree of effect, particularly when using modern EC products. Confidence intervals were wide for data on AEs, SAEs and other safety markers. Overall incidence of SAEs was low across all study arms. We did not detect any clear evidence of harm from nicotine EC, but longest follow‐up was two years and the overall 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‐to‐date information for decision‐makers, this review is now a living systematic review. We will run searches monthly from December 2020, with the review updated as relevant new evidence becomes available. Please refer to the Cochrane Database of Systematic Reviews for the review’s current status.
FURTHER READING
Science Media Centre, expert reaction to a Cochrane review of e-cigarettes for smoking cessation, as published in the Cochrane Database of Systematic Reviews, 2020
The New England Journal of Medicine, A Randomized Trial of E-Cigarettes versus Nicotine Replacement Therapy, 2019
Cochrane Systematic Review, Electronic cigarettes for smoking cessation, 2016
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