Introduction
Electronic cigarettes (EC), handheld devices that vaporize a liquid to produce an inhalable aerosol, have become increasingly popular as a potential aid for smoking cessation. Since their appearance in the market, consumers, healthcare professionals, and policy makers have been exploring whether ECs are effective and safe alternatives to traditional nicotine replacement therapies (NRT) or other cessation strategies.
This article summarizes the findings from the most recent update of a living systematic review assessing the safety, tolerability, and effectiveness of ECs for helping people who smoke achieve long-term smoking abstinence, in comparison to other cessation methods or no treatment. The continual updating ensures that new evidence is integrated regularly to guide informed decisions in public health.
Background and Rationale
Smoking tobacco remains a leading cause of preventable disease and death worldwide. Quitting smoking substantially lowers risks of cardiovascular disease, cancer, respiratory illness, and other health issues. Despite many available cessation aids, long-term abstinence rates remain modest, prompting a search for more effective tools.
Electronic cigarettes deliver nicotine without combustion, reducing exposure to many harmful tobacco smoke constituents. However, uncertainties have persisted regarding their effectiveness for quitting smoking, potential adverse effects, and long-term safety profile. This systematic review update consolidates evidence from randomized controlled trials (RCTs) and observational studies up to March 2025, to provide comprehensive insight.
Objectives
The primary goal was to evaluate the safety and effectiveness of nicotine-containing electronic cigarettes to help people who smoke tobacco quit smoking long term. Comparisons were made against non-nicotine ECs, other smoking cessation treatments such as nicotine replacement therapy or behavioral support, and no treatment.
Methods
Multiple databases including Cochrane CENTRAL, MEDLINE, Embase, and PsycINFO were searched to identify relevant studies up to 1 March 2025. Additional efforts involved reference checking and contacting study authors for unpublished data.
Included were randomized trials allocating smokers to either EC or controls, as well as uncontrolled intervention studies where all participants used ECs. Studies were required to measure outcomes such as smoking abstinence after at least six months, adverse events (AEs), and serious adverse events (SAEs), along with other biomarkers related to toxicant exposure.
Risk of bias was evaluated using the RoB 1 tool, and evidence certainty was graded with the GRADE approach. Where possible, meta-analyses using random-effects models were conducted to calculate pooled risk ratios (RRs) or mean differences with 95% confidence intervals (CIs).
Summary of Included Studies
The review included 104 studies, encompassing 30,366 participants. Among them, 61 were randomized controlled trials with the remainder being observational or uncontrolled studies. About 11 studies were deemed at low risk of bias, with the majority at high or unclear risk due to design limitations.
Key Findings on Effectiveness
Evidence showed that nicotine-containing ECs significantly increased quit rates compared to traditional nicotine replacement therapy (NRT), supported by high-certainty evidence. Specifically, nicotine EC users were about 1.55 times more likely to quit smoking than those using NRT, translating roughly to an additional 3 quitters per 100 users.
Compared to non-nicotine ECs, nicotine ECs also probably increase quit rates (moderate certainty), although with less precision in estimates. Similarly, compared to behavioral support or no support, nicotine EC use may yield higher cessation rates, though this evidence was of low certainty due to potential biases.
Safety and Tolerability
The incidence of adverse events (AEs), such as throat irritation, headache, cough, and nausea, appeared similar between nicotine EC and other groups, with most symptoms diminishing over time with continued EC use. Serious adverse events (SAEs) were rare across all study arms.
There was insufficient evidence to conclusively rule out differences in serious adverse event rates between EC and other methods due to very serious imprecision and relatively small event counts. Also, while some evidence suggested a slight increase in non-serious AEs with nicotine EC compared to no behavioral support, the certainty of this finding was very low.
Other Outcomes
Few studies reported on biomarkers, toxicant exposure, or longer-term EC use, limiting conclusions in these areas. The data available did not indicate significant differences in safety markers between nicotine and non-nicotine EC users.
Clinical and Public Health Implications
This systematic review update provides strong evidence supporting the use of regulated nicotine-containing electronic cigarettes as an effective smoking cessation aid, outperforming nicotine replacement therapies in promoting quitting among smokers. Importantly, no serious safety concerns have emerged from the studied trials, though longer-term and larger studies are warranted to fully characterize long-term safety.
Health professionals may consider recommending nicotine ECs to smokers seeking alternatives to conventional cessation options, keeping in mind individual patient preferences and regulatory context. Meanwhile, patients should be advised about typical mild adverse effects that often resolve with continued use.
Limitations and Future Research
The main limitation of the evidence is imprecision for some outcomes and comparisons, mainly due to relatively few large, well-powered randomized controlled trials. Many existing studies had design or reporting limitations that introduced bias risk.
Notably, the review included trials of regulated nicotine-containing EC products; the safety and efficacy profiles for illicit products or those containing other substances such as tetrahydrocannabinol (THC) may differ.
Ongoing randomized trials are expected to add valuable evidence. This review remains “living,” with monthly literature surveillance and periodic updates to inform practice and policy as new data emerges.
Conclusion
Nicotine-containing electronic cigarettes increase smoking cessation rates compared to nicotine replacement therapy and likely to non-nicotine ECs. Adverse events are generally mild and transient with no detected serious harm, though evidence is limited by imprecision and study quality. Nicotine ECs appear to be a promising and effective smoking cessation aid within a comprehensive tobacco control framework.
Funding and References
This work was supported by Cancer Research UK (PICCTR-2024/100012).
Reference: Lindson N, Livingstone-Banks J, Butler AR, McRobbie H, Bullen CR, Hajek P, Wu AD, Begh R, Theodoulou A, Notley C, Rigotti NA, Turner T, Fanshawe T, Hartmann-Boyce J. Electronic cigarettes for smoking cessation. Cochrane Database Syst Rev. 2025 Nov 10;11(11):CD010216. doi: 10.1002/14651858.CD010216.pub10. PMID: 41212103; PMCID: PMC12599494.
