June 15, 2015

Stanton A. Glantz, PhD

More evidence that e-cigs are depressing quitting smoking in the real world

Erin Sutfin and colleagues at Wake Forest University just published “ The Impact of Trying Electronic Cigarettes on Cigarette Smoking by College Students: A Prospective Analysis” in American Journal of Public Health that adds to the evidence that e-cigarette use is depressing quitting smoking cigarettes.
This paper follows several hundred college students over 3 years during which time they assessed smoking behavior, how often respondents smoked (a measure of nicotine dependence) other tobacco use, and a variety of personality and demographic characteristics.  Controlling for all these factors, the authors found that among young adults who were smoking at baseline, e-cigarette use was associated with higher likelihood of smoking at follow-up.
Here is the abstract:

Objectives. We assessed the impact of trying e-cigarettes on future cigarette smoking in a sample of college student smokers.
Methods. In this longitudinal study, first-semester college students at 7 colleges in North Carolina and 4 in Virginia completed a baseline survey and 5 follow-up surveys between fall 2010 and fall 2013. Current cigarette smoking at wave 6 was the primary outcome. Participants (n = 271) reported current cigarette smoking at baseline and no history of e-cigarette use. We measured trying e-cigarettes at each wave, defined as use in the past 6 months.
Results. By wave 5, 43.5% had tried e-cigarettes. Even after controlling for other variables associated with cigarette smoking, trying e-cigarettes was a significant predictor of cigarette smoking at wave 6 (adjusted odds ratio [AOR] = 2.48; 95% confidence interval [CI] = 1.32, 4.66), as was friends’ cigarette smoking (AOR = 4.20; 95% CI = 2.22, 7.96) and lifetime use of other tobacco products (AOR = 1.63; 95% CI = 1.22, 2.17).
Conclusions. Trying e-cigarettes during college did not deter cigarette smoking and may have contributed to continued smoking. (Am J Public Health. Published online ahead of print June 11, 2015: e1–e7. doi:10.2105/AJPH.2015.302707)

Put in terms of the odds of quitting, use of e-cigarettes is associated with reduced quitting with an adjusted odds ratio of 0.40 (95% CI 0.21-0.76), consistent with the overall findings of the rest of the studies of the effects of e-cigarette use on quitting conventional cigarettes.
This is, of course, good news for the multinational cigarette companies, which are increasingly dominating the e-cigarette business.



This is subject to reverse causality; those who quit naturally are less lkely to subsequently experiment with ecigs. Furthermore, ever-use is such a week measure that it's very hard to weed out the confounding.
Furthermore, observational studies find negative associations with approved cessation aids as well, because of confounding and reverse causality http://www.ncbi.nlm.nih.gov/pubmed/18201639.


... because the stimulus (in this case e-cigarette use) is measured <em;before</em; the outcome (continued smoking at a later point in time).
The study you cite is a cross-sectional, not a longitudinal, study.


Thanks for the clarification.
New question: now that I understand that those who had already quit by wave 5 were excluded (don't have full text), then there is considerable selection bias due to the fact that those who tried EC and quit cigarettes before wave 5 are excluded fom the ecig user sample.


"These findings suggest that for college students smokers, trying e-cigarettes and, in particular, repeated e-cigarette use is a predictor of continued cigarette smoking."


this is unfair, you responded but did not post my response: if the stimulus was measured before the possible outcome than only dual users were included making this a biased sample.


The paper is available.&nbsp; You should read the whole thing rather than expect me to explain it to someone who has only read the abstract.&nbsp; The paper is very carefully done using established methods.


The study compared quitting cigarettes among people who did (dual users) and did not use (cigarettes only) c-cigarettes concurrently with cigarettes at baseline.

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