|Year : 2018 | Volume
| Issue : 2 | Page : 94-102
Role of E-Cigarettes in smoking cessation: A systematic review
Irfan Ali, Basavaraj Patthi, Ashish Singla, Ravneet Malhi, Lav Kumar Niraj, Kuldeep Dhama
Department of Public Health Dentistry, D. J. College of Dental Sciences and Research, Modinagar, Uttar Pradesh, India
|Date of Submission||15-Jan-2018|
|Date of Acceptance||27-Mar-2018|
|Date of Web Publication||24-May-2018|
Dr. Irfan Ali
Department of Public Health Dentistry, D. J. College of Dental Sciences and Research, Modinagar, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Introduction: E-cigarettes (EC) are devices that heat liquid into an aerosol that user inhales. Youth are using EC at increasing and alarming rates. The tobacco industry aggressively markets EC to youth, glamorizing EC use in advertisements, and offering EC in candy flavors such as bubble gum and gummy bears. The liquid usually in EC has nicotine and other additives which is addictive. Aim: The purpose of this study was to systematically review the role of e-cigarettes in smoking cessation. Materials and Methods: A literature review was performed; PubMed, PubMed Central and Cochrane Library, Embase, and Google Scholar were searched from 1970 to December 2017 to identify appropriate studies. Results: Out of the total 817 titles appeared, 17 articles fulfilled the criteria and were selected for the review. Two articles which were hand searched and one article which was through E-mail was also included in this review. EC have a direct impact on smokers and efficiency in quitting smoking was assessed very low. Majority of the study found that EC could increase the risk of smokers developing nicotine dependence and thus evidence on smoking reduction was found very low. Conclusions: There are relatively a few studies evaluating the role of EC in smoking cessation. EC products are marketed in a wide variety of channels that have broad reach among youth and young adults, including magazines, television, radio, and the Internet. More randomized controlled trials and longitudinal studies are needed to further clarify the role of EC in smoking cessation.
Keywords: E-cigarette, nicotine, smokers, smoking cessation, tobacco
|How to cite this article:|
Ali I, Patthi B, Singla A, Malhi R, Niraj LK, Dhama K. Role of E-Cigarettes in smoking cessation: A systematic review. J Indian Assoc Public Health Dent 2018;16:94-102
|How to cite this URL:|
Ali I, Patthi B, Singla A, Malhi R, Niraj LK, Dhama K. Role of E-Cigarettes in smoking cessation: A systematic review. J Indian Assoc Public Health Dent [serial online] 2018 [cited 2018 Jun 18];16:94-102. Available from: http://www.jiaphd.org/text.asp?2018/16/2/94/233069
| Introduction|| |
Tobacco is the leading preventable cause of death which is estimated to have killed 100 million people in the 20th century worldwide, and by the 21st century the figure could reach 1 billion. Cigarette smoking remains at the top among many of the risk factors for preventable death and disease. Smoking not only affects individuals inhaling the toxic fumes but also affects those that are exposed to second-hand smoke. The appearance of vaporized nicotine products widely referred to as electronic cigarettes or e-cigarettes (EC) has provided consumers with an alternative means of nicotine intake. EC is mostly popular among adult smokers, most of the adult's starts using e-cigarettes to quit smoking or for smoking reduction, EC contain a heating unit that aerosolizes vegetable glycerin and/or propylene glycol mixed with flavorings and various concentrations of nicotine (or no nicotine). EC are battery-powered devices that heat a solution usually propylene glycol or glycerol, but in most cases, nicotine and also flavorings agents to deliver an aerosol that is inhaled by the user. To know about the effect of EC, US Preventive Services Task Force (2015) has done a survey and found that the use of EC in adults is not recommend for tobacco cessation.
Tobacco use imposes the immense burden of disease and death and is responsible for social, health, economic, and environmental effects. Tobacco consumption in India is responsible for half of all cancers in men and quarter of all cancer found in women. India holds the second position in the world for production and stands third in the consumption of tobacco. Although nicotine replacement therapies (NRTs; nicotine gum, patch, lozenges, sprays, and inhalers), bupropion SR, and varenicline has been widely used for smoking cessation; however, rates remain obstinately low. ECs provide taste and throat sensation which is similar to cigarette smoking than those provided by the nicotine inhalator. The vapor that looks like tobacco smoke is only visible when the user exhales after drawing on the mouthpiece, not when the device is being held. There are hundreds of different brands and models of EC available. In 2012 and 2014, Goniewicz found that nicotine content, flavors, and other components of different brands and model of EC differ in the composition. This makes a blanket assessment of cessation efficacy difficult. Earlier EC models resemble the combustible cigarettes in shape and are disposable, whereas newer types are rechargeable, use refillable cartridges, and may have variable power settings. Various industries are trying to increase their production are claiming that ECs are effective cessation supports. However, the results are substantially low. Till date, five systematic reviews have been published that investigate the efficacy or effectiveness of ECs for cessation. Franck et al. reviewed seven studies published before September 2013, of which three were assessed using the Cochrane criteria. They concluded that there remains significant uncertainty about the efficacy of ECs for cessation due to methodological weaknesses.
This systematic review addresses the role of EC in tobacco cessation aids. To address the rapidly changing landscape of research on EC in an environment where high-quality evidence remains scarce, we undertook a comprehensive review of both the published peer-reviewed and gray literature, until November 2017. This review is the most comprehensive to date and includes several studies published since the Cochrane review, and others were completed. It employs a rigorous design to thoroughly assess the evidence from various disciplines and methodological approaches, taking into account methodological weaknesses of individual studies during data synthesis.
Research question – To review the effect of EC as cessation aids.
The aim of this study is to estimate EC as an effective tool in smoking cessation.
| Materials and Methods|| |
The articles which were published in English, dated from the year 1970 to November 2017 were included in this review. The search terms for articles were the terms either in the title or abstract. Full-text original research articles were taken. Unpublished articles in the press and personal communications were excluded from this review. Our focus was to be broad in scope to include as much relevant existing data as reasonably possible.
- Original research articles, i.e., RCT and prospective cohort studies that looked into the role of EC as a smoking cessation tool.
- Experimental/Animal studies and Review articles
- Case series, Cases reports, and Letters to the Editors
- Articles where only abstracts are available.
Types of outcome measures
Due to substantially higher relapse rates associated with short-term abstinence from smoking, our analysis focuses only on abstinence and reduction outcomes measured at follow-up points of at least 30 days. The body of evidence related to primary and secondary cessation outcomes was assessed using the GRADE system adopted by the Cochrane Collaboration for evidence quality evaluation.
Search method for identification of studies
For the identification of the studies included in this review, we devised the search strategy for each database. The search strategy used a combination of controlled vocabulary and free text terms. The main database was PubMed, PubMed Central, Cochrane Review, Embase, and Google Scholar [Figure 1].
- PubMed (1970–2017)
- PubMed Central (1970–2017)
- Cochrane Review (1970–2017)
- Embase (1970–2017)
- Google Scholar (1970–2017).
The search also included the hand search of the journals fulfilling the inclusion criteria for the review.
| Results|| |
Risk of bias in the included study
The risk of bias in the two RCTs which contribute to the cessation was low across all domains., The only exception was in the reporting bias in Caponnetto et al. 2013, as it was unclear if the original intention was to combine the two nicotine-containing EC groups or not. The lost-to-follow-up rate (LTFU) was 22% in Bullen et al. Although the patch group had higher LTFU and withdrawal than the EC group (patch: 27%; nicotine-EC: 16%; placebo EC: 22%), there was minimal difference between the per-protocol and ITT analyses, and hence, we deemed attrition bias to be at low risk. LTFU rates were similar among the three arms at 12 months in Caponnetto et al. 2013 (35% in 7.2 mg nicotine group; 37% in 5.4 mg nicotine group; 45% in no-nicotine group).
In Adriaens et al., in 2014, a further RCT not included in the cessation due to limited detail available; we rated all other domains as low risk of bias.
We categorized all other included studies, by nature of their design, as being at high risk of selection bias. Ten of these did not blind participants or personnel and given the nature of the study, follow-up measures and contact with researchers, we judged them to be at risk of selection or performance bias or both. In the other studies, the lack of intervention or contact with researchers means that there is unlikely to be significant performance or detection bias.
For many of the cohort studies, we were unable to determine prespecified outcomes and hence rated these as being at unclear risk of reporting bias. Finally, Ely 2013 did not define abstinence, and it was unclear if the completion of the program was at 6 months after enrolment, or at an earlier time point. We, therefore, judged this study to be at high risk of other bias [Table 2] and [Table 3].
Effects of interventions
Randomized control trials
In the trial comparing EC to patch (Bullen et al. 2013), there was no significant difference in 6-month CO-validated continuous abstinence between the treatment arms (7.3%, 5.8%, and 4.1%, in the nicotine EC, patch, and placebo EC arms, respectively). In the other RCT, 1-year abstinence rates (at least 6 months of not smoking and carbon monoxide-validated) were higher in the two nicotine EC arms (13% and 9%) compared with the placebo EC group (4%). In our analysis, we combined the two nicotine EC arms and compared these with the placebo group. The difference was not statistically significant.,
Among the intervention cohort studies that enrolled smokers unmotivated to quit, Polosa et al. 2011 reported abstinence rates (30-day point prevalence, CO-validated abstinence) of 22.5% at 6 months and 12.5% at 2 years. Pacifici 2015 reported cessation rates of 52.9% at 12 months, but did not define how cessation was measured. Polosa et al., in 2014, reported 36% (18/50) 7-day point prevalence abstinence rates at 6 months, which were CO-validated. In the study of highly-dependent smokers with schizophrenia, 14% (2/14) achieved abstinence (CO-validated) at 1 year. In Ely 2013, 43.8% (21/48) of participants were abstinent from smoking at the completion of the 6-month program. In the one intervention cohort study in which motivation to quit was not defined, 42.2% of participants (30/71) were abstinent at 6 months, with similar numbers at 12 months (40.8%, 29/71; 30-day, self-reported point prevalence abstinence). In Adriaens et al 2014, a randomized controlled trial (RCT) in which all participants were provided with nicotine-containing ECs at 8 weeks and which we hence treat as a cohort study for cessation purposes, 19.6% of participants were abstinent at 8 months (10/51) using CO validation.
The longitudinal surveys from the first version of this review contained relatively a few smokers who were using ECs at baseline.
Etter and Bullen 2014 showed 1-year self-reported abstinence rates of 45.7% (16/35) among the responders who used ECs at baseline. In Grana et al. 2014, the 1-year abstinence rate was 10% (9/88) in smokers who had used ECs (at least once in the past 30 days) at baseline, compared to 13.8% (119/861) in nonEC users. The difference between EC and nonEC users was not statistically significant. No information was provided on whether people were using ECs for cessation or reduction before baseline, or whether they used any EC at all during the follow-up period. A study by Al-Delaimy et al. 2015 found 1-year self-reported prolonged abstinence (1 month or longer) rates of 5% (12/236) in people who reported ever using EC at baseline, compared to 10.5% (32/306) in participants who indicated they would never use EC at both baseline and follow-up; the authors report that ever use of EC predicted a lower likelihood of cessation in a multivariable analysis (odds ratio [OR] 0.41, 95% confidence interval [CI] 0.18–0.93). In Borderud et al. 2014, 14.5% (denominator unknown) of participants who reported EC use in the past 30 days at baseline were abstinent at 12 months (self-reported 7-day point prevalence abstinence), compared with 30% of nonEC users. In an ITT analysis correcting for a range of predictors, nonEC users were found to be more likely to quit than EC users (OR 2.00, 95% CI 1.23–3.26); although, there was no significant difference in a complete case analysis. It was not possible to calculate ITT data for Brose 2015; at one year, 8.1% of people who reported daily EC use at baseline (7/86) reported being ex-smokers, compared to 9.5% (25/263) of people who reported nondaily EC use at baseline and 12.9% (168/1307) of non-EC users. Compared with nonuse, daily EC use at baseline was neither significantly associated with cessation at follow-up (OR 0.62, 95% CI 0.28–1.37) nor was nondaily EC use. In Manzoli et al. 2015, sustained (30-day) smoking abstinence was reported at 12 months, with CO validation in a subsample of participants. The authors reported that there was no significant difference in abstinence between EC users and nonusers (summary statistic not provided), with 16% (51/319) of those who reported baseline EC use abstinent at 12 months compared with 15% (101/693) of people who did not use EC at baseline.
To assess the effects of ECs on smoking, participants need to be recruited before initiating EC use. In future versions of this review, as higher quality data become available, we will no longer include this group of studies [Table 1].
| Discussion|| |
Summary of main results
This update includes further 11 studies. However, no new RCTs evaluating smoking cessation at 6 months or longer were available, and the conclusions of this review have not substantively changed. As the results of two RCTs, covering 662 participants showed that smokers who used nicotine electronic cigarettes (ECs) were significantly more likely to stop smoking than smokers using placebo ECs. The effect size (5%) is small, but not unusual given the low level of behavioral support provided. There was no evidence of statistical heterogeneity, despite the differences in study designs. In one of the trials that evaluated it, a first-generation EC with low nicotine delivery was as effective as nicotine patches in helping smokers to quit long-term, but CIs were wide.
Although the two RCTs were well conducted and judged to be at low risk of bias, we categorize the quality of the evidence overall as low, because of the small number of trials on which it is based (see summary of findings for the main comparison). We would be more confident in the findings if there were more studies available, and are encouraged by the increase in ongoing studies collected as part of this review update. None of the included studies reported serious adverse events considered possibly related to EC use. One of the included studies detected a severe adverse event considered possibly related to EC use, which was the advent of itchy throat and cough in a participant with a history of childhood asthma. This resolved once EC use was discontinued. No studies detected a significant increase in adverse events in people using ECs. The most commonly reported AEs were local irritation of the throat and mouth. One of the RCTs. measured AEs at baseline and then across the study duration, and showed that the frequency of respiratory symptoms (e.g., cough and shortness of breath) decreased over time, which is likely to be secondary to changes in cigarette smoking. This finding was supported by data from observational cohort studies.
Agreements and disagreements with other studies or reviews
There are various reasons why RCTs provide different answers from many observational studies in this area. These include variations in the effectiveness of ECs depending on the level of support provided, issues around definitions of baseline EC usage, and unexplored confounders. This is not an issue specific to ECs: cohort studies of NRT show clear evidence that failure to adjust for confounders leads to estimates that suggest NRT is ineffective, while including adjustment for variables related to tobacco dependence supports its effectiveness. In addition, those studies which analyze results in smokers based on EC use at baseline have by the nature of their design already excluded people who have successfully quit using EC, and therefore, only retain participants who, at entrance to the study, would be classed as “treatment failures” or are in the middle part of a cessation attempt involving cutting down to quit.
Following the standard methods of the Cochrane Tobacco Addiction Group and the protocol for this review, we focused on evidence from RCTs for cessation outcomes, although we also analyzed cohort studies which provided interpretable data. Despite their differences, the one area in which all systematic reviews of ECs for smoking cessation agree is that more evidence is needed. The majority of recent systematic reviews in this area sound a note of cautious optimism when it comes to the use of EC as a smoking cessation aid, but the evidence base is limited, particularly in comparison with smoking cessation treatments with established efficacy, such as traditional forms of NRT, varenicline and bupropion. Uncertainty remains as to the long-term safety profile of ECs, given their relatively new position in the market. Expert consensus broadly holds that, based on all available evidence, ECs are considerably safer than traditional cigarettes, but further studies are needed to establish their safety profile compared with established smoking cessation aids.
| Conclusions|| |
The current review provides strong evidence that EC are associated with initiation of cigarette smoking among youth; however, the controversy as to whether EC use “causes.”
Cigarette-smoking initiation will undoubtedly persist. In fact, the findings from our study provide support for both sides of the debate. It is highly plausible that “common factors” account for a substantial proportion of increased cigarette-smoking initiation among EC users. At the same time, it would be foolhardy to dismiss the likelihood that early exposure to nicotine via EC increases smoking uptake. Attributing the relative importance of these 2 factors will not be straightforward, and represents a critical challenge to the research community. In the meantime, regulatory frameworks that succeed in shifting EC use away from youth and concentrating their use among cigarette smokers for the purposes of smoking cessation are likely to have the greatest public health impact.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]