Most of the discussion of the effects of e-cigarette use on smoking has focused on their gateway effect among youth (they are) and whether e-cigs help smokers quit (as consumer products they do not) . There has been much less attention to how e-cigarettes affect the risk of relapse among former smokers.
But now there are studies of relapse. Laura Barufaldi and her colleagues at the National Cancer Institute of Brazil recently published Risk of smoking relapse with the use of electronic cigarettes: A systematic review with meta-analysis of longitudinal studies that identified six relevant studies from the US, UK and France, three of which have quantitative results. They found that risk of relapse is doubled among former smokers who use e-cigarettes than among non-users (relative risk 2.03; 95% CI 1.39-2.96).
They limited themselves to longitudinal studies (where people are followed forward in time) of people who were not smoking cigarettes at the beginning of the study. (One of he studies required that the smokers had quit 5 years before the study started; the others varied in the length of time having quit.) This is important because, as the authors note, “[t]he smoking abstinence at baseline shows that the exposure to e-cigarettes occurred before smoking relapse, ensuring the association’s temporality.”
They also separated the results based on intensity of e-cigarette use (experimentation or past use, occasional use, and daily use). As shown in the figure above (from the paper), relapse was elevated in all three groups, although it only approached statistical significance at the 95% level. The increase in relapse was statistically significant for occasional users.
The authors comment that that these results may be due to:
Although past use or current regular use of e-cigarettes equally demonstrate an increased risk of smoking relapse in our study, the result was not statistically significant. Amid uncertainties, it is possible that experimenting with e-cigarettes, without a progression towards sustainable use, is not enough for former smokers to recover their smoking habit, while its daily use supplies the need for nicotine especially among those with a higher degree of dependence. Indeed, a multi-center cross-sectional study, comparing the indicators of nicotine dependence and relapse between former smoker non-users and daily users of e-cigarettes, demonstrated higher levels of addiction, before and after cessation, in those who daily use nicotine through e-cigarettes. Moreover, these individuals reported greater confidence in staying abstinent from conventional cigarettes, despite having a similar desire to smoke30. Thus, by replacing nicotine delivery products, highly dependent former smokers could prevent smoking relapse, but may start using e-cigarettes.
Later in the paper they note that the failure to reach statistical significance in the experimenters and daily users may be due to lack of power.
There are two other points to be made about these findings. First, occasional e-cigarette use is the most common use pattern. Second, and more important from a policy perspective, the overall effect of e-cigarette use across all e-cig users is to double the risk of relapse. It is this overall effect that the FDA and other regulators need to use in their assessment of the effects of e-cigarettes on relapse because it is reflecting how e-cigarettes as consumer products are actually being used in the population.
Here is the abstract:
Introduction: The use of e-cigarettes has been the subject of a public health debate on their possibility of undermining efforts for tobacco control. The aim of this study was to synthesize the risk of smoking relapse with the use of e-cigarettes by former smokers.
Methods: MEDLINE, EMBASE, PsycInfo and LILACS were searched without restriction to language or date of publication. Longitudinal observational studies evaluating the association between e-cigarette use and smoking relapse were selected by two independent reviewers, and disagreements solved by discussion with a third researcher. Data extraction and risk of bias assessment were also carried out by two independent reviewers. The meta-analysis was performed using the random effect Mantel-Haenszel model.
Results: From 632 retrieved records, six studies were eligible and described, while three were included in the quantitative synthesis. The studies were conducted in the USA, UK and France, with final sample size varying from 374 to 4094 former smokers. Risk of relapse was 2.03 (95% CI: 1.39-2.96) among former smoker users than non-users of e-cigarettes, and 1.38 (95% CI: 1.11-1.65) when pooling the adjusted association measures. Long-term former smokers were the main contributors for the higher relapse risk, while the impact of frequency of exposure to e-cigarettes (past, non-daily, daily) was uncertain.
Conclusions: Considering the growing popularity of e-cigarettes among former smokers, our results point to the great potential for an increase in the frequency of relapse to conventional smoking and vaping for those who move to regular use of e-cigarettes.
The full citation is: Barufaldi LA, Guerra RL, de Albuquerque RCR, Nascimento A, Chança RD, de Souza MC, de Almeida LM. Risk of smoking relapse with the use of electronic cigarettes: A systematic review with meta-analysis of longitudinal studies. Tob Prev Cessat. 2021 Apr 27;29:29. doi: 10.18332/tpc/132964. PMID: 33928198; PMCID: PMC8078138. It is available here.