Evidence that e-cig use patterns associated with quitting smoking: daily users quit more; everyone else quits less

The new paper by Daniel Giovenco and Christine Delnevo, “Prevalence of population smoking cessation by electronic cigarette use status in a national sample of recent smokers,” contributes to the emerging picture that intensive users of e-cigarettes are more likely to have stopped smoking while incidental users quit less.
The cross-sectional study (snapshot in time) uses the 2014 and 2015 National Health Interview Survey (NHIS) to examine the association between e-cigarette use and being a former smoker.  The found that daily e-cigarette users were about 3 times more likely to be former cigarette smokers than non-e-cigarette users.  (The e-cigarette advocates have been making a big deal about this finding.)
At the same time, they found that non-daily e-cigarette users were about 3 times less likely to be former smokers, i.e. e-cigarette use was associated with significantly less quitting.  (The e-cigarette advocates didn’t mention this result.)  This distinction is important because non-daily users comprise about 2/3 of all current e-cigarette users in the study.
This paper is consistent with several other papers that have shown more quitting cigarettes among intensive e-cigarette users and less quitting among non-intensive users, which is the dominant use pattern.
Here is the abstract:
INTRODUCTION:  Amid decreasing rates of cigarette smoking and a rise in e-cigarette use, there is a need to understand population patterns of use to inform tobacco control efforts and evaluate whether e-cigarettes may play a role in tobacco harm reduction.
METHODS:  This study merged data from the 2014 and 2015 National Health Interview Survey (NHIS) and restricted the sample to recent smokers [i.e., current smokers and former smokers who quit in 2010 or later (n=15,532)]. Log-binomial regression estimated adjusted prevalence ratios (aPR) for being quit by e-cigarette use status (i.e., daily, some day, former trier, never). All analyses controlled for factors traditionally correlated with smoking cessation.
RESULTS:  A quarter of the sample (25.2%) were former smokers. The prevalence of being quit was significantly higher among daily e-cigarette users compared to those who had never used e-cigarettes [52.2% vs. 28.2%, aPR: 3.15 (2.66, 3.73)]. Those who used e-cigarettes on some days were least likely to be former smokers (12.1%). These relationships held even after accounting for making a quit attempt and use of other tobacco products.
CONCLUSIONS:  Among those with a recent history of smoking, daily e-cigarette use was the strongest correlate of being quit at the time of the survey, suggesting that some smokers may have quit with frequent e-cigarette use or are using the products regularly to prevent smoking relapse. However, the low prevalence of cessation among infrequent e-cigarette users highlights the need to better understand this subgroup, including the individual factors and/or product characteristics that may inhibit cessation.
The full citation is:  Giovenco DP, Delnevo CD.  Prevalence of population smoking cessation by electronic cigarette use status in a national sample of recent smokers.  Addict Behav. 2017 Aug 3;76:129-134. doi: 10.1016/j.addbeh.2017.08.002. [Epub ahead of print]