I just came upon Real-world effectiveness of smoking cessation aids: A population survey in England with 12-month follow-up, 2015-2020 that uses the UK Smoking Toolkit Study to quantify the effectiveness of e-cigarettes and various medical therapies on smoking cessation among smokers were were trying to quit. In this longitudinal study Sarah Jackson and colleagues followed 1045 adult smokers forward in time for a year to see how they did in remaining smoke-free. What they found was that smokers who used e-cigarettes for smoking cessation were no more likely to succeed than those who didn’t.
They qualified the association between e-cigarette use and successful smoking cessation using an adjusted odds ratio, which equals 1.0 if there is no association, is greater than 1.0 if e-cigarettes help people quit and less than 1.0 if they inhibit quitting. In and analysis that controlled for level of addiction, demographics and use of other smoking cessation methods, Jackson and colleagues found no statistically significant association. Specifically, while the point estimate of the odds ratio of 1.12 was above 1.0, the 95% confidence interval (also called the “margin of error”) extended from 0.82 to 1.53, i.e., included possible values both blow and above 1.0. This is also quantified with p=0.489, which is not even close to significant (which is usually considered p<0.05). So, this is pretty strong evidence that e-cigarettes have no effect on smoking cessation.
They defined “cessation” as “no longer smoking cigarettes,” not “nicotine free,” so respondents could be still using e-cigarettes.
As Jackson and colleagues point out, this is a different conclusion than from an earlier cross-sectional analysis of the same data that showed cessation benefit associated with e-cigarettes. In contrast to longitudinal studies, where subjects are followed forward in time, cross-sectional studies are based on an observed relationship at a single point in time. While cross-sectional studies are useful, longitudinal studies are generally considered stronger evidence. This is particularly true in areas such as smoking cessation, where people tend to relapse over time, so cessation interventions generally perform worse the longer you wait.
Indeed, longer term followup studies (over 3 years) in the US show e-cigarette use associated with significantly less quitting.
Jackson’s results are consistent with our earlier meta-analysis that found no statistically significant association between e-cigarettes and quitting among smokers motivate to quit (OR 0.85, 95% CI 0.68-1.06) based on 24 studies of motivated smokers.
Jackson and colleagues say that we found less quitting associated with e-cigarettes, perhaps because the longitudinal studies in our meta-analysis showed significantly depressed quitting, but we prefer to focus on the overall result that includes all the available studies.
Because of their interpretation of our meta-analysis, they went on to do additional statistical analysis (based on Bayes Theorem) to conclude that their results “were inconclusive regarding a benefit of e-cigarettes for cessation but showed use of e-cigarettes was unlikely to be associated with reduced odds of cessation.” I did not find this part of their analysis compelling because their overall result (p=0.489) was nowhere near statistically significant and the Bayes calculations are based on specific assumed effects that may not be reasonable.
But the primary findings of no association with cessation are fine.
Another important finding Jackson et al report is that varenicline, a prescription cessation medicine, more than doubled the odds of successful smoking cessation (OR=2.69; 95% CI 1.43-5.05; p=0.002). NRT, whether by prescription or over-the-counter, was not significantly associated with smoking cessation.
In addition to adding to the evidence base that, even in England, e-cigarettes as consumer products are not effective for cessation, this study points to the fact that comparisons of e-cigarettes with NRT is not the appropriate comparison for e-cigarettes as medicines: They should be compare with varenicline.
It’s also time for the National Health Service and others in England to stop recommending e-cigarettes for quitting.
Here is the abstract:
Objective: To examine the real-world effectiveness of popular smoking cessation aids, adjusting for potential confounders measured up to 12 months before the quit attempt.
Methods: 1,045 adult (≥18y) smokers in England provided data at baseline (April 2015-November 2020) and reported a serious past-year quit attempt at 12-month follow-up. Our outcome was smoking cessation, defined as self-reported abstinence at 12 months. Independent variables were use in the most recent quit attempt of: varenicline, prescription NRT, over-the-counter NRT, e-cigarettes, and traditional behavioural support. Potential confounders were age, sex, social grade, alcohol consumption, and level of dependence (measured at baseline), variables relating to the most recent quit attempt (measured at 12-month follow-up), and survey year.
Results: Participants who reported using varenicline in their most recent quit attempt had significantly higher odds of abstinence than those who did not, after adjustment for potential confounders and use of other aids (OR = 2.69, 95 %CI = 1.43-5.05). Data were inconclusive regarding whether using prescription NRT, over-the-counter NRT, e-cigarettes, or traditional behavioural support was associated with increased odds of abstinence (p > 0.05; Bayes factors = 0.41-1.71, expected effect size OR = 1.19), but provided moderate evidence that using e-cigarettes was more likely associated with no effect than reduced odds (Bayes factor = 0.31, expected effect size OR = 0.75).
Conclusions: Use of varenicline in a quit attempt was associated with increased odds of successful smoking cessation. Data were inconclusive regarding a benefit of e-cigarettes for cessation but showed use of e-cigarettes was unlikely to be associated with reduced odds of cessation. Associations between other cessation aids and cessation were inconclusive.
The full citation is: Jackson SE, Kock L, Kotz D, Brown J. Real-world effectiveness of smoking cessation aids: A population survey in England with 12-month follow-up, 2015-2020. Addict Behav. 2022 Dec;135:107442. doi: 10.1016/j.addbeh.2022.107442. Epub 2022 Jul 25. PMID: 35908322; PMCID: PMC9587352. It is available here.