Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. Among the nearly 100 reviews produced by the Cochrane Tobacco Addiction Group, their review of the use of electronic cigarettes in smoking cessation is now being managed as a living systematic review, with monthly searches to keep an eye on the evidence base, so that the published review can be refreshed as necessary. The review was re-badged as a living review in 2021 and its fourth update in this format was published in January 2024. Here's one of the authors, Ailsa Butler from the University of Oxford in the UK to summarise the latest findings.

Ailsa: Electronic cigarettes, or e-cigarettes or vapes are handheld electronic devices which produce an aerosol by heating a liquid, which usually contains nicotine and flavourings. People who smoke, healthcare providers and regulators want to know if these can help people quit smoking, and if they are safe to use for this purpose. To provide them with answers they need, our review examines the effectiveness and safety of using e-cigarettes to help people stop smoking tobacco cigarettes. We compare e-cigarettes to other smoking cessation treatments, to non-nicotine e-cigarettes, and to no treatment. And, for the first time, we have now carried out a network meta-analysis combining direct and indirect evidence.
We did the searches for this update up to July 2023 and now include 88 completed studies, with 10 being added for this update. In total, the studies included more than 27,000 adults who smoked and 47 of the 88 studies were randomized trials. Most of the studies took place in the USA, UK, and Italy.
Turning to the results, based on seven studies with two and a half thousand participants, we found high-certainty evidence that people are more likely to stop smoking for at least six months if they use nicotine e-cigarettes rather than nicotine replacement therapy. In the comparison with e-cigarettes that don't contain nicotine, six studies in 1600 adults provide moderate-certainty evidence that e-cigarettes with nicotine increase quit rates. Lastly, research comparing nicotine e-cigarettes with usual care or no treatment also suggests benefit, based on data from 5000 people in 9 studies. However, this is less certain due to risk of bias inherent in this open-study design. The results of the network meta-analyses were consistent with those findings from the pairwise meta-analyses for all critical outcomes.
In regard to safety, the number of adverse events were similar for nicotine and non-nicotine e-cigarettes and for nicotine e-cigarettes and nicotine replacement therapy. The overall incidence of serious adverse events was low across all study arms and we did not detect evidence of serious harm from nicotine e-cigarettes, but the longest follow-up was two years and the number of studies was small.
To make sure that our review continues to provide up-to-date information for decision-makers, this review is a living systematic review, as mentioned by Mike. Living reviews are systematic reviews that are regularly updated, allowing for new evidence to be incorporated as it becomes available. They are well suited to e-cigarette or vape research where uncertainties surrounding the effects on smoking cessation hamper policy, clinical, and personal decisions and where the topic is fast moving, and changes in the interpretation and certainty of the evidence may affect policy and healthcare decisions.
We will continue to monitor the research on this topic and update this review as necessary, not least because we still need more evidence, particularly about the effects of newer types of e-cigarettes that have better nicotine delivery than older types, which might help more people quit smoking.

Mike: To read the current version of this living review and to watch for its next update, just visit Cochrane Library dot com and search 'electronic cigarettes for smoking cessation' to find it.