Evidence that ecigs help smokers trying to quit; overall evidence still shows ecigs depress smoking cessation

Tarik Benmarhnia and colleagues recently published “Can e-Cigarettes and Pharmaceutical Aids Increase Smoking Cessation and Reduce Cigarette Consumption? Findings from a Nationally Representative Cohort of American Smokers” in American Journal of Epidemiology.   Using the large longitudinal FDA/NIDA PATH dataset they found that, among people trying to stop smoking cigarettes, e-cigarette users were more successful than non-e-cigarette users.  They also found no significant difference in quitting cigarettes between smokers who were using e-cigarettes and using FDA-approved therapies. 

Simon Chapman pointed out to me that those who didn’t use e-cigarettes or FDA-approved methods were more likely to have stopped all tobacco than those using the other products. 

This paper differs from an earlier study using the same dataset by Berry et al in two ways:  (1) the new paper only considered smokers who were trying to quit cigarettes whereas Berry et al considered everyone, and (2) the new paper controlled for potential confounders using propensity score matching rather than considering them in a multivariate model.   Despite these differences, the results of the two papers are not all that different.  The new paper found that e-cigarette use was associated with a significant increase in the odds of having stopped cigarettes a year later of 1.52 (95% CI 1.14, 2.02), whereas Berry et al found 1.46 (0.95, 2.23) among everyone one.  (Benmarhnia did not publish the OR; they emailed it to me when I asked for it.) 

I added the new paper into my running meta-analysis. Even with this positive finding, the overall body of evidence still shows that e-cigarettes are associated with less quitting among smokers (pooled OR 0.766, 95% CI 0.609, 0.963).  (It is probably not appropriate to add both these studies into the meta-analysis at the same time because they both used the same data, but doing so will amplify their effect and bias the estimate towards more quitting.  Even with this bias, the overall estimate of the effect on quitting is negative.)

Here is the abstract for the Benmarhnia  paper:

Many smokers believe that electronic nicotine delivery systems (ENDS) and pharmaceutical cessation aids can help them quit smoking or reduce cigarette consumption, but the evidence for e-cigarettes to aid quitting is limited. Examining 3,093 quit attempters in the nationally-representative US Population Assessment of Tobacco and Health (PATH) Study between 2013 and 2015, we evaluated the influence of ENDS and pharmaceutical cessation aids on persistent abstinence (≥30 days) from cigarettes, and reduced cigarette consumption, using Propensity Score Matching to balance comparison groups on potential confounders and multiple imputation to handle missing data. At PATH Wave 2, 25.2% of quit attempters reported using ENDS to quit during the previous year, making it the most popular cessation aid in 2014-15. More quit attempters were persistently cigarette abstinent than persistently tobacco abstinent (15.5±0.8% vs 9.6±0.6%). Using ENDS to quit cigarettes increased the probability of persistent cigarette abstinence at Wave 2 (Risk Difference (RD)=6%; 95% CI: 2%;10%), but using approved pharmaceutical aids did not (varenicline RD=2%; 95% CI: -6%,13%; buproprion RD=4%, 95% CI: -6%, 17%; NRT RD=-3%, 95% CI -8%, 2%). Among quit attempters who relapsed, ENDS did not reduce the average daily cigarette consumption (-0.18 cigarettes per day; 95% CI: -1.87;1.51).

The full citation is:  Benmarhnia T, Pierce JP, Leas E, White MM, Strong DR, Noble ML, Trinidad DR.  Can e-Cigarettes and Pharmaceutical Aids Increase Smoking Cessation and Reduce Cigarette Consumption? Findings from a Nationally Representative Cohort of American Smokers.  Am J Epidemiol. 2018 Jun 27. doi: 10.1093/aje/kwy129. [Epub ahead of print].  It is available here.