A new overview of the best available evidence worldwide for smoking cessation has found that nicotine‑containing e‑cigarettes appear to be more effective for smoking cessation than other interventions such as nicotine replacement therapy (nicotine patches, gum, lozenges, etc.) e-cigarettes with no nicotine, and behavioural support.

This ‘overview’ of systematic reviews summarises existing evidence from several systematic reviews and makes the findings more accessible. The overview pooled the evidence from fourteen systematic reviews of smoking cessation interventions from 2014 to 2023.

Findings from higher-quality reviews consistently showed greater smoking cessation with nicotine-containing e‑cigarettes than other interventions. Lower-quality reviews produced more variable and imprecise estimates. When restricted to higher-quality evidence, results consistently favoured nicotine e‑cigarettes over nicotine replacement therapy, non-nicotine e-cigarettes, and other comparators.

The overview also created an ‘Evidence and Gap Map’ (EGM) to identify gaps in the current evidence that urgently need to be filled.  There are currently no high-quality systematic reviews directly comparing nicotine e-cigarettes with cytisine, bupropion, or nicotine pouches.  Also, direct evidence comparing nicotine e-cigarettes with varenicline is extremely limited, with only a single small trial at high risk of bias.

The EGM also showed that current evidence of serious adverse events associated with e-cigarettes is inconclusive, and that most of the studies collected data from high-income countries.  Future primary research on e-cigarettes for smoking cessation should continue to collect data on serious adverse events and expand its data collection to include low-and middle-income countries.

Lead author DrAngela Difeng Wu, Senior Researcher and Lecturer at the Nuffield Department of Primary Care Health Sciences, University of Oxford, says “We hope this overview and Evidence and Gap Map can lay to rest some claims that evidence is ‘mixed’ regarding the impacts of nicotine e-cigarettes on smoking abstinence.  In fact, the evidence is clear and consistent across all of the meta-analyses we consulted:  e-cigarettes are effective at helping people stop smoking.”