A Cochrane Review of more than 78 studies and 22 000 participants found the strongest evidence yet that e-cigarettes (vapes) work better than traditional nicotine replacement therapies, like patches and chewing gums, at helping people give up smoking. However, researchers say the long-term health effects of e-cigarettes are still unknown.
The research found “high certainty evidence that people are more likely to stop smoking for at least six months using nicotine e-cigarettes, or ‘vapes’, than using nicotine replacement therapies, and that nicotine e-cigarettes led to higher quit rates than e-cigarettes without nicotine, or no stop smoking intervention, but less data contributed to these analyses”.
The updated Cochrane report included an addition of 22 studies since the last update in 2021.
The World Health Organisation (WHO) said in 2020 that 22.3% of the global population used tobacco, despite it killing up to half of its users. Stopping smoking reduces the risk of lung cancer, heart attacks and many other diseases. Though most people who smoke want to quit, many find it difficult to do so permanently. Nicotine patches and gum are safe, effective and widely used methods to help individuals quit.
E-cigarettes heat liquids with nicotine and flavourings, allowing users to “vape” nicotine instead of smoking. Data from the review showed that if six in 100 people quit by using nicotine replacement therapy, eight to 12 would quit by using electronic cigarettes containing nicotine. This means an additional two to six people in 100 could potentially quit smoking with nicotine containing electronic cigarettes.
Dr Jamie Hartmann-Boyce, associate professor at the University of Oxford, editor of the Cochrane Tobacco Addiction Group, and an author of the new publication, said: “Electronic cigarettes have generated a lot of misunderstanding in both the public health community and the popular press since their introduction more than a decade ago. These misunderstandings discourage some people from using e-cigarettes as a stop smoking tool. Fortunately, more and more evidence is emerging and provides further clarity.
“With support from Cancer Research UK, we search for new evidence every month as part of a living systematic review. We identify and combine the strongest evidence from the most reliable scientific studies currently available.
“For the first time, this has given us high-certainty evidence that e-cigarettes are even more effective at helping people to quit smoking than traditional nicotine replacement therapies, like patches or gums.”
In studies comparing nicotine e-cigarettes to nicotine replacement treatment, significant side effects were rare. In the short-to-medium term (up to two years), nicotine e-cigarettes most typically caused throat or mouth irritation, headache, cough and feeling nauseous. However, these effects appeared to diminish over time.
Dr Nicola Lindson, university research lecturer at the University of Oxford, Cochrane Tobacco Addiction Group’s managing editor, and author of the publication, said: “E-cigarettes do not burn tobacco; and as such they do not expose users to the same complex mix of chemicals that cause diseases in people smoking conventional cigarettes. E-cigarettes are not risk free, and shouldn’t be used by people who don’t smoke or aren’t at risk of smoking.
“However, evidence shows that nicotine e-cigarettes carry only a small fraction of the risk of smoking. In our review, we did not find evidence of substantial harms caused by nicotine containing electronic cigarettes when used to quit smoking. But due to the small number of studies and lack of data on long-term nicotine-containing electronic cigarette usage – usage over more than two years – questions remain about long-term effects.”
The researchers conclude that more evidence, particularly about the effects of newer e-cigarettes with better nicotine delivery than earlier ones, is needed to assist more people quit smoking. Longer-term data is also needed.
Michelle Mitchell, chief executive at Cancer Research UK, said: “We welcome this report which adds to a growing body of evidence showing that e-cigarettes are an effective smoking cessation tool. We strongly discourage those who have never smoked from using e-cigarettes, especially young people. This is because they are a relatively new product and we don’t yet know the long term health effects.
“While the long term effects of vaping are still unknown, the harmful effects of smoking are indisputable – smoking causes around 55 000 cancer deaths in the UK every year. Cancer Research UK supports balanced evidence-based regulation on e-cigarettes from UK governments which maximises their potential to help people stop smoking, while minimising the risk of uptake among others.”
Study details
Electronic cigarettes for smoking cessation
Jamie Hartmann-Boyce, Nicola Lindson, Ailsa Butler, Hayden McRobbie, Chris Bullen, Rachna Begh, Annika Theodoulou, Caitlin Notley, Nancy Rigotti, Tari Turner, Thomas Fanshawe, Peter Hajek.
Published in Cochrane Library on 17 November 2022
Abstract
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 organisations, 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.
Selection criteria
We included randomised controlled trials (RCTs) and randomised cross‐over trials, in which people who smoke were randomised 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.
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‐randomised studies), and the remainder at unclear risk.
There was high certainty that quit rates were higher in people randomised to nicotine EC than in those randomized to nicotine replacement therapy (NRT) (RR 1.63, 95% CI 1.30 to 2.04; I2 = 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; I2 = 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; I2 = 34%; 5 studies, 2411 participants).
There was moderate‐certainty evidence, limited by imprecision, that quit rates were higher in people randomised to nicotine EC than to non‐nicotine EC (RR 1.94, 95% CI 1.21 to 3.13; I2 = 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; I2 = 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; I2 = 0%; 8 studies, 1272 participants).
Compared to behavioural support only/no support, quit rates were higher for participants randomised to nicotine EC (RR 2.66, 95% CI 1.52 to 4.65; I2 = 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 randomised to nicotine EC (RR 1.22, 95% CI 1.12 to 1.32; I2 = 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; I2 = 38%; 9 studies, 1993 participants).
Data from non‐randomised 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.
Cochrane Library article – Electronic cigarettes for smoking cessation (Open access)
See more from MedicalBrief archives:
E-cigarette Summit: Vaping improves odds of quitting tobacco smoking
Vaping among teens at SA’s affluent schools ‘a significant problem’
Major independent evidence review: vaping ‘a small fraction’ of the risk of smoking