Electronic cigarettes for smoking cessation have become an increasingly discussed topic among healthcare providers, policymakers and people who smoke. These handheld electronic vaping devices produce aerosol for inhalation by heating an e-liquid, typically containing nicotine, propylene glycol, glycerol and flavors. While some organizations have discouraged their use for quitting smoking due to concerns about safety and effectiveness, recent scientific evidence provides important insights into whether electronic cigarettes can help people quit tobacco. A comprehensive systematic review analyzing data from 61 studies representing 16,759 participants offers the most current evidence on electronic cigarettes for smoking cessation, examining both effectiveness and safety profiles across multiple comparisons and outcomes.

Understanding Electronic Cigarette Types and Nicotine Delivery

Electronic cigarettes for smoking cessation come in various forms, each with different nicotine delivery capabilities that may influence effectiveness. Early models resembled traditional cigarettes and used disposable cartridges, often called cig-a-likes, but these typically delivered very low amounts of nicotine to users. More recent refillable tank models allow users to fill a transparent container with their choice of e-liquid, generally providing faster and more efficient nicotine delivery. These devices usually permit a wider choice of flavors and nicotine concentrations, and experienced vapers who manage to switch completely to vaping typically use these models. The newest pod devices use nicotine salt formulations that reduce irritant effects while delivering higher nicotine levels that closely mimic the rapid nicotine delivery from conventional cigarettes, despite having lower battery power than tank models.

The variation in device types presents both opportunities and challenges for understanding electronic cigarettes for smoking cessation. Different devices may differ significantly in their ability to help people quit smoking because they deliver nicotine at different rates and levels. Nicotine itself represents the active ingredient that helps relieve withdrawal symptoms, making nicotine delivery an important consideration. Research suggests that devices providing less nicotine may actually pose higher risks in some ways, because users must puff with higher intensity to obtain desired nicotine levels, and more intensive puffing accompanies increased inhalation of potential toxicants. Throughout this discussion, we distinguish between nicotine-containing electronic cigarettes and non-nicotine versions, with the latter sometimes considered placebo devices, though they can also function as interventions themselves by providing sensorimotor and behavioral replacement for smoking.

Electronic Cigarettes Compared to Nicotine Replacement Therapy

The comparison between electronic cigarettes for smoking cessation and traditional nicotine replacement therapy provides particularly relevant evidence for healthcare providers and people considering quitting options. Pooled data from four randomized controlled trials involving 1,924 participants showed that quit rates were higher in people assigned to nicotine electronic cigarettes than in those assigned to nicotine replacement therapy products like patches or gum. Specifically, the analysis found a 53% increase in quit rates for nicotine electronic cigarettes compared to nicotine replacement therapy. In practical terms, this translates to an additional three quitters per 100 people using nicotine electronic cigarettes instead of nicotine replacement therapy, with the range potentially extending from one to six additional quitters per 100 people.

The certainty of this evidence was judged to be moderate, meaning researchers have reasonable confidence that the true effect lies close to this estimate, though some uncertainty remains. The main limitation reducing certainty involved imprecision due to the relatively small number of studies and participants. Studies contributing to this comparison used different electronic cigarette types, including cartridge devices, refillable tank models and one pod device. Despite these differences in device types, statistical analysis found no meaningful heterogeneity in results, suggesting the benefit held across different electronic cigarette models. However, researchers emphasize that confidence intervals were wide for several outcomes, and additional research would strengthen conclusions about electronic cigarettes for smoking cessation compared to nicotine replacement therapy.

Nicotine Content Matters for Quitting Success

Comparing nicotine-containing electronic cigarettes to non-nicotine versions helps isolate the specific effect of nicotine delivery in electronic cigarettes for smoking cessation. Five randomized controlled trials involving 1,447 participants provided data for this comparison, all testing cartridge-style devices. Results showed quit rates were 94% higher in people randomized to nicotine electronic cigarettes compared to non-nicotine electronic cigarettes. In absolute terms, this means an additional seven people per 100 would successfully quit smoking using nicotine electronic cigarettes instead of non-nicotine versions, with the range potentially spanning from two to 16 additional quitters per 100 people. The certainty of evidence was again judged to be moderate, with imprecision remaining the primary limitation.

This comparison provides important insights because it specifically tests whether nicotine delivery through electronic cigarettes contributes to smoking cessation success. The non-nicotine electronic cigarette still provides the behavioral, sensorimotor and social aspects of using an electronic cigarette, including hand-to-mouth motion, inhalation sensations and visible aerosol that mimics smoke. The fact that nicotine-containing versions showed substantially higher quit rates suggests that nicotine delivery plays an important role in the effectiveness of electronic cigarettes for smoking cessation. This finding aligns with established understanding that nicotine helps relieve withdrawal symptoms that make quitting difficult, while the sensorimotor aspects of electronic cigarettes may address behavioral and social elements of smoking that people miss when they quit.

Electronic Cigarettes Versus Behavioral Support Alone

Six randomized controlled trials involving 2,886 participants compared electronic cigarettes for smoking cessation to behavioral support alone or to no support. This comparison showed quit rates were 161% higher for participants randomized to nicotine electronic cigarettes, translating to an additional six quitters per 100 people, with the range potentially extending from two to 15 additional quitters per 100. However, researchers judged the certainty of this evidence to be very low due to issues with both imprecision and risk of bias. The risk of bias concern arose because these studies could not use blinding, and different levels of support between groups could have influenced results beyond just the effect of the electronic cigarette itself.

Despite the lower certainty rating, this comparison provides valuable context when considered alongside the other comparisons. Both the comparison with non-nicotine electronic cigarettes and the comparison with nicotine replacement therapy found benefits for nicotine electronic cigarettes. The former isolates the effect of nicotine delivery through electronic cigarettes, while the latter isolates the effect of the sensorimotor and behavioral elements provided by electronic cigarettes. Given that both comparisons found benefits for nicotine electronic cigarettes for smoking cessation, it follows logically that comparing nicotine electronic cigarettes to minimal intervention would show even larger benefits, since this comparison captures both the pharmacological effects of nicotine and the behavioral replacement aspects of electronic cigarette use.

Safety Profile and Adverse Events

Understanding the safety profile represents a critical component of evaluating electronic cigarettes for smoking cessation. The comprehensive review examined both adverse events, defined as any undesirable experience, and serious adverse events, defined as events requiring hospitalization, causing disability or death. Comparing nicotine electronic cigarettes to nicotine replacement therapy, pooled data from two studies involving 485 participants found no clear difference in the rate of adverse events between groups. Serious adverse events were rare overall, occurring in only a small number of participants across all study arms. When comparing nicotine to non-nicotine electronic cigarettes, three studies involving 601 participants again found no difference in adverse event rates, and six studies involving 1,033 participants found insufficient evidence to determine whether rates of serious adverse events differed between groups.

The most commonly reported adverse events across all studies included throat or mouth irritation, headache, cough and nausea. Importantly, seven studies that tracked adverse events over time found that these effects tended to decrease as people continued using electronic cigarettes, suggesting an adaptation period. No studies detected serious harms considered related to electronic cigarette use during follow-up periods extending up to two years. However, researchers emphasize that confidence intervals were often wide for safety outcomes, and the overall incidence of serious adverse events was low across all study arms, making it difficult to detect potential differences. Long-term effects beyond two years remain unknown, representing an important area where more evidence is needed to fully characterize the safety profile of electronic cigarettes for smoking cessation.

Biomarkers and Health Indicators

Beyond adverse events, researchers examined various biological markers and health indicators in people using electronic cigarettes for smoking cessation. These measurements provide objective data about potential health effects and exposure to harmful substances. Studies measured carbon monoxide levels, which serve as an indicator of smoke exposure, finding that carbon monoxide decreased more in people using nicotine electronic cigarettes compared to those using non-nicotine electronic cigarettes or no support. When comparing nicotine electronic cigarettes to nicotine replacement therapy, two studies found slightly greater carbon monoxide reductions with electronic cigarettes, though the difference was small and confidence intervals were wide.

Several studies also measured exposure to various toxicants and carcinogens, substances known to cause cancer or other health problems. Studies examined compounds like NNAL, which comes from tobacco-specific nitrosamines, and various metabolites of volatile organic compounds. Results generally showed reductions in these harmful substances when people who smoked switched to using electronic cigarettes for smoking cessation, though the magnitude of reduction varied across different compounds and studies. Lung function measurements in several studies showed either improvements or no significant changes when people switched from smoking to electronic cigarettes. Blood pressure and heart rate data showed mixed results across studies, with small changes observed that were difficult to interpret clinically. These biomarker findings suggest that switching from smoking to electronic cigarettes may reduce exposure to harmful substances, though more long-term data would strengthen conclusions.

Continued Use of Electronic Cigarettes

An important consideration for electronic cigarettes for smoking cessation involves how long people continue using these products after quitting smoking. Evidence from randomized controlled trials provided mixed findings. Comparing electronic cigarettes to nicotine replacement therapy, one study found no difference in continued product use at six months, while another found that people assigned to electronic cigarettes were substantially more likely to still be using them compared to those assigned to nicotine replacement therapy. This suggests that some people who quit smoking using electronic cigarettes may use them longer than they would use other cessation aids. Two studies comparing nicotine to non-nicotine electronic cigarettes found slightly more people still using electronic cigarettes in the nicotine groups, though the difference was small and confidence intervals were wide.

From a public health perspective, continued electronic cigarette use among people who have quit smoking represents a complex issue. On one hand, any continued nicotine use represents ongoing dependence. On the other hand, electronic cigarettes expose users to substantially fewer toxicants than combustible cigarettes, and some continued use may be preferable to returning to smoking. Additionally, given the difficulty many people experience when trying to quit smoking, having a product that helps them quit and that they find satisfying enough to continue using could be viewed as a benefit rather than a limitation. The key consideration remains that people stop smoking combustible tobacco completely, as this provides the largest health gains, whether or not they continue using electronic cigarettes.

Conclusion

Electronic cigarettes for smoking cessation show promise based on moderate-certainty evidence that nicotine electronic cigarettes increase quit rates compared to nicotine replacement therapy and compared to non-nicotine electronic cigarettes. Evidence comparing nicotine electronic cigarettes with behavioral support alone also suggests benefit, though with less certainty due to study design limitations. In practical terms, an additional three to seven people per 100 might be expected to quit smoking successfully by using nicotine electronic cigarettes instead of these alternatives. Confidence intervals were wide for most safety outcomes, but researchers detected no evidence of serious harms, with the most common side effects being throat irritation, headache and cough that typically resolved with continued use. More studies are needed to confirm effect sizes, evaluate newer device types like pods, and establish long-term safety profiles beyond the current maximum of two years follow-up.

Reference

1. Hartmann-Boyce J, McRobbie H, Butler AR, Lindson N, Bullen C, Begh R, Theodoulou A, Notley C, Rigotti NA, Turner T, Fanshawe TR, Hajek P. Electronic cigarettes for smoking cessation. Cochrane Database Syst Rev. 2021;9:CD010216.