A thorough analysis of global evidence suggests that nicotine e-cigarettes may be more effective than traditional smoking cessation aids, but safety uncertainties and research gaps remain and the debate is far from settled.
Research: Electronic cigarettes for smoking cessation: a systematic review and overview of the evidence and gap map. Image credit: StockLab/Shutterstock.com
Electronic cigarettes, or vapes, are often offered to help people kick their smoking habits, but there are still uncertainties, especially regarding their safety, and the suggested benefits of smoking cessation. Recently published reviews addiction We summarize existing research to assess the safety and effectiveness of e-cigarettes for this purpose, identify remaining gaps, and outline plans for future primary intervention studies.
How electronic cigarettes deliver nicotine without burning cigarettes
VAPE is an electronic cigarette that produces an aerosol by heating e-liquid contained in pods, which are cartridges that can be replaced or refilled. The liquid may or may not contain nicotine or other flavors.
Smoking remains the leading preventable cause of cancer, death and increased morbidity among disadvantaged people, both globally and in the UK. Health organizations and professional groups say e-cigarettes carry a lower risk of these outcomes than cigarettes.
However, the role of e-cigarettes in helping people quit smoking remains internationally debated and important to consumers, healthcare providers, and regulators, despite growing meta-analytic evidence supporting their effectiveness.
Summary of 14 systematic reviews and 109 studies
The current study was designed to systematically review existing reviews, synthesize and summarize the evidence, and make it readily accessible. The researchers aimed to extend the evidence presented by the EC’s Cochrane Living Systematic Review (LSR) on smoking cessation.
The researchers included 14 systematic reviews of intervention studies published since 2015. These covered 109 primary studies. Reviews were evenly divided between high and low quality reviews, and most of the available evidence came from high-income countries.
The population sample included the general population, pregnant women, people with other pre-existing conditions, and people at high risk for lung cancer. These reviews are not exhaustive, but often cover the same subject matter.
In addition, they created the Evidence and Gap Map (EGM), a web-based tool that visually depicts where evidence is lacking in a particular research area, to help frame policy and direct research.
VAPE may outperform NRT
There were 21 meta-analyses comparing e-cigarettes and other nicotine replacement therapies (NRTs). Both studies showed that nicotine-containing e-cigarettes are more effective for quitting smoking than other e-cigarettes. For example, compared to various nicotine replacement treatments such as skin patches and gum, nicotine e-cigarettes increased the risk of quitting by 17 to 67 percent.
The direction of the effect was consistently positive across studies. If only high-quality evidence is considered, the evidence points in the same direction.
Nevertheless, it is important to note that statistical uncertainty exists Across multiple reviews, some confidence intervals suggest There is little or no difference. The authors point out publication bias, unacceptable methodology, small sample sizes, and other technical deficiencies in several reviews.
Combination of nicotine e-cigs and NRT
A single high-quality review compared nicotine VAPE in combination with NRT and NRT alone, and nicotine VAPE in combination with NRT and non-nicotine VAPE in combination with NRT. These analyzes showed greater efficacy for the combination of nicotine e-cigarettes and NRT compared to NRT alone or non-nicotine combinations. This was contradicted by a low-quality review that suggested no statistically significant differences.
VAPE and Placebo
Nicotine vaping, regardless of quality, appeared to be more beneficial than a placebo in smoking cessation in various studies. Results show that compared to placebo, nicotine e-cigarettes increased quit rates, more than tripling rates in some analyses, although some estimates had wide confidence intervals and were imprecise.
Vaping and behavioral support or no support
Nicotine-containing e-cigarettes were more effective than behavioral support or no support, but non-nicotine e-cigarettes did not show this benefit, and estimates were often inconsistent with an advantage or clear difference.
Additionally, only one small, low-quality trial directly compared nicotine e-cigarettes and varenicline, a drug used to help people quit smoking. This trial suggested that varenicline may be more effective, but was limited by its small size and high risk of bias. Indirect evidence showed no clear difference between the two.
Safety of nicotine e-cigarettes
Adverse events were not consistently increased across studies compared to NRT, placebo, non-nicotine e-cigarettes, e-cigarette and NRT combinations, or heated tobacco. This review revealed a complicated picture, mainly due to several reported incidents and inaccurate reporting. Nicotine e-cigarettes may be associated with a small increase in adverse events compared to behavioral support or no support.
Evidence gaps still exist when comparing major smoking cessation drugs
The EGM revealed that little evidence is available on the comparative effectiveness of nicotine e-cigarettes and NRT and behavioral support or no support in supporting smoking cessation over 6 months. There was little evidence comparing nicotine vapes with cytisine, bupropion, and nicotine pouches.
Evidence regarding physiological outcomes (e.g., heart rate, blood pressure, exposure to toxic substances) was limited and primarily derived from a small subset of studies, with heterogeneous reporting across the evidence base.
strengths and limitations
Despite this systematic review using rigorous research methods in line with Cochrane reviews, several limitations exist, including grouping single and combination nicotine replacement therapies for comparison, omitting studies published after April 2024, and excluding ongoing studies from the evidence and gap map following standard practice.
Nicotine e-cigarettes show consistent benefits for smoking cessation
Overall, the study showed a clear trend toward benefiting smoking cessation for at least 6 months with nicotine e-cigarette use compared to several common smoking cessation approaches such as NRT, placebo/non-nicotine e-cigarettes, and behavioral support.
Our hope is that, given the clear consistency of results across meta-analyses, this overview and EGM can cast doubt on some claims that the evidence is “mixed” regarding the effects of EC on smoking cessation.
Evidence across socio-economic and geographic variations is limited, with few studies from low- and middle-income countries. Studies identifying serious adverse events have yielded inconsistent results.
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