New study using PATH data shows that e-cigarettes help some smokers quit, hurt most

Kaitlyn Berry and colleagues just published “E-cigarette initiation and associated changes in smoking cessation and reduction: the Population Assessment of Tobacco and Health Study, 2013–2015,” a well-done analysis of the FDA/NIH path dataset  that concludes that “daily e-cigarette initiators were more likely to have quit smoking or reduced use compared to non-users.  However, less frequent e-cigarette use was not associated with cigarette cessation/reduction.”

This paper adds to the growing body of evidence that the kind of e-cigarette is important as well as how intensely it is used matters.  As they stated in the abstract (quoted above), they only found significantly more quitting among daily e-cigarette users.  An important point in considering how to interpret this result is that only 19% of e-cigarette users are daily users.

Among the rest,  they found less quitting than among smokers who did not use e-cigarettes at all (OR .51 [95% CI 0.26-1.00, P=.05 for experimenters [ 54% of the e-cigarette users] and 0.51 [0.17-1.47, p=.206] among some day e-cig users [27% of e-cig users]).  Thus, which e-cigarettes were associated with increased quitting among some users, the depress quitting among the largest group of users (the experimenters).

While these results are reported and mentioned in the Discussion, I think that they should have been given more emphasis in the abstract and conclusions. 

Most important, it means that e-cigarettes as used in the real world are not reducing overall smoking.  In one of the sensitivity analyses Berry et al did (Table S1), they found that e-cigarette use overall was not associated with quitting (OR 1.46 [0.95, 2.23], p=0.081).

The importance of the device and use pattern is further emphasized in another of their sensitivity analyses (Table S5), where they found that daily use of the tank systems was driving their finding of benefits among daily users; that group saw a highly significant increase in quitting (OR 10.14 [5.37-10.12], p<.001; there must be a typo in their table since the point estimate is outside the 95% confidence interval) with experimental or some day use of cartridge systems (cig-alikes) associated with significantly less quitting (0.30 [0.10-0.88], p=.029).  Experimental or some day use of tank systems and daily use of cartridge systems was not associated with any significant changes in quitting.  These results are consistent with the other available studies.

One of the particularly interesting things that the authors of this paper did is based the study on smokers who had never used an e-cigarette at baseline and looked at how their smoking changed a year later when they initiated e-cigarette use after baseline.

There is also an analysis of the association between e-cigarette use and reducing smoking by 50% which shows similar patterns.  I don’t think that this is a useful endpoint, particularly for heart disease where the dose-response is so nonlinear.  Indeed, smoking a single cigarette a day has about half the risk of heart attack and stroke of being a pack a day smoker.  I was surprised that the paper made such a big deal about smoking reduction since several of the authors are experts in heart disease.  This point wasn’t even mentioned.  In any event, until there is convincing evidence of substantial individual and public health benefit of cutting down, I with people would stop using this endpoint.

These criticisms of how the authors chose to present their results and what they did and did not emphasize, however, does not detract from the excellent statistical analysis that they did in this very strong paper.

Here is the abstract:

BACKGROUND: The role of electronic cigarettes (e-cigarettes) in product transitions has been debated.

METHODS: We used nationally representative data from the Population Assessment of Tobacco and Health Study waves 1 (2013-2014) and 2 (2014-2015) to investigate the associations between e-cigarette initiation and cigarette cessation/reduction in the USA. We limited the sample to current cigarette smokers aged 25+ years who were not current e-cigarette users at wave 1. We modelled 30-day cigarette cessation and substantial reduction in cigarette consumption as a function of e-cigarette initiation between surveys using multivariable logistic regression.

RESULTS: Between waves 1 and 2, 6.9% of cigarette smokers who were not current e-cigarette users transitioned to former smokers. After adjusting for covariates, cigarette smokers who initiated e-cigarette use between waves and reported they used e-cigarettes daily at wave 2 had 7.88 (95% CI 4.45 to 13.95) times the odds of 30-day cigarette cessation compared with non-users of e-cigarettes at wave 2. Cigarette smokers who began using e-cigarettes every day and did not achieve cessation had 5.70 (95% CI 3.47 to 9.35) times the odds of reducing their average daily cigarette use by at least 50% between waves 1 and 2 compared with e-cigarette non-users.

CONCLUSIONS:  Daily e-cigarette initiators were more likely to have quit smoking cigarettes or reduced use compared with non-users. However, less frequent e-cigarette use was not associated with cigarette cessation/reduction. These results suggest incorporating frequency of e-cigarette use is important for developing a more thorough understanding of the association between e-cigarette use and cigarette cessation.

The full citation is Berry KM, Reynolds LM, Collins JM, et al E-cigarette initiation and associated changes in smoking cessation and reduction: the Population Assessment of Tobacco and Health Study, 2013–2015.  Tobacco Control Published Online First: 24 March 2018. doi: 10.1136/tobaccocontrol-2017-054108 and it is available here.