September 2021 update to the Cochrane living review of electronic cigarettes for smoking cessation

In this episode Jamie Hartmann-Boyce and Nicola Lindson discuss the emerging evidence in e-cigarette research and two recent publications by the group: the September 2021 update to the Cochrane living review of electronic cigarettes for smoking cessation; and a response to a paper by Pisinger et al 2020. This podcast is a companion to our Cochrane living systematic Review and shares the evidence from monthly searches and review findings.
Jamie and Nicola discuss the team's response to a paper by Pisinger and Vestbo 2020, and underline that the aim of the Cochrane process is to always focus on the evidence (DOI: 10.1183/13993003.02117-2021 or link).
They then outline the findings of the September update to the review which includes five new studies that have been added since the April 2021 version and includes search findings up to 1st May 2021. Overall the review includes 61 studies representing 16,759 participants. The main findings remain the same and some new comparisons have been included. There is still moderate certainty that nicotine containing e-cigarettes help more people to quit at 6 months or longer compared to e-cigarettes without nicotine or than NRT (nicotine replacement therapy). Uncertainty also still exists around nicotine containing e-cigarettes compared to no intervention (e.g. continued smoking). This reflects that the quality of the evidence is considered very low according to Cochrane standards. There is moderate certainty evidence that neither nicotine e-cigarettes nor non-nicotine e-cigarettes result in higher numbers of adverse or serious adverse effects.

Turning to new comparisons this update includes a study of a pod device (Russell et al), the findings were consistent with the other included studies that showed that more people quit at 6 months or longer using EC than with NRT. This update also includes a study comparing nicotine salt to free-base nicotine e-cigarettes; no clear differences were found between the two. We also included studies that provided 'dual users' (people who already use EC and tobacco cigarettes) with advice on how to use their EC to quit smoking; in one study there was no usable data in a second larger study (Martinez) there was a marginally better quit rate, however there was no clear evidence of benefit.

In response to feedback, for the first time in this update, data is included on the proportion of participants still using e-cigarettes or quitting aids) at six months or longer. Data from two studies comparing nicotine EC with NRT were notably different, with one finding no difference in the proportion of participants still using study product at longest follow-up, and the other finding significantly higher levels of EC use than NRT. There was no evidence for a difference in the proportion of people still using EC at longest follow-up in two studies comparing nicotine EC with non-nicotine EC. For all other studies the majority of participants that had been given nicotine EC at the start of the study were still using EC at 6 months or longer. Jamie and Nicola discuss the different ways that this result could be interpreted. It will be important to collect more information on this outcome.

For more information on the September Cochrane review see: https://doi.org/10.1002/14651858.CD010216.pub6 or our webpage.

Jamie and Nicola also bring us up to date with the literature search conducted on August 1st and September 1st. The August search found one linked study by Rubenstein et al 2021 (doi: 10.1016/j.addbeh.2021.107037) and two new ongoing studies (El-Khoury et al 2021 (doi: 10.1136/bmjopen-2021-048859); and NCT04708106 2021). No new studies were found in the September 1st search. We will include the studies we've found in future updates of the Cochrane review.