Response to Letter Regarding Article, “Electronic Cigarettes: A Scientific Review”
Our article1 reviewed the 5 population-based studies of the relationship between e-cigarette use and smoking cessation available at the time. All 5 revealed less cigarette cessation among smokers who used e-cigarettes than among smokers who did not use e-cigarettes. We pooled these results in a meta-analysis and found significantly less quitting among smokers who used e-cigarettes than smokers who did not use e-cigarettes (odds of quitting, 0.61; 95% confidence interval, 0.50–0.75)
Herzig lists possible problems with the studies and so dismisses the overall conclusion. We recognized these limitations in our article. Most important, we recognized that “A limitation of 3 of these studies [including Adkinson et al2] is that they did not control for level of nicotine dependence. It is possible that more dependent smokers, who would have more difficulty quitting in general, would be the ones who would be more likely to experiment with e-cigarettes, which could contribute to the finding that e-cigarette use is associated with a lower quit rate.”
Since publication of our article, 3 additional relevant papers have been published. Brown et al3 reported in a cross-sectional among smokers in the UK that has similar limitations to the 5 studies in our meta-analysis the use of e-cigarettes as part of a serious quit attempt resulted in more successful quitting compared with those not using e-cigarettes. Biener and Hargraves’4 longitudinal study of smokers found that, controlling for level of nicotine addiction and demographics, intensive e-cigarette users were more likely to have quit smoking than smokers who did not use e-cigarettes. They also found that intermittent e-cigarette users were no more or less likely to have stopped smoking than nonusers, but were more likely to expect that they would still be smoking 1 year later. Borderud et al5 conducted a longitudinal study of cancer patients who smoke and were enrolled in an organized smoking cessation program. Controlling for level of addiction, e-cigarette users were equally likely to quit as nonusers at follow-up, and in the intent-to-treat analysis were less likely to have quit.
The reality is, of course, that there is no such thing as a perfect study. The fact that there are modest differences in methodology between the 5 studies in our meta-analysis is not an issue because the Q test for heterogeneity does not even approach statistical significance (P=0.269). Moreover, the fact that there are consistent outcomes among these 5 studies, despite the methodological differences, strengthens the confidence we can have in our conclusion that, among all smokers (including both smokers who are not and who are using e-cigarettes as part of a serious quit attempt), e-cigarette use is associated on balance with less cigarette smoking cessation.
Rachel Grana, PhD, MPH
Neal Benowitz, MD
Stanton Glantz, PhD
Center for Tobacco Control Research and Education and Department of Medicine
University of California San Francisco
San Francisco, CA
Dr Benowitz is a consultant to pharmaceutical companies that market smoking cessation medications and has been an expert witness in litigation against tobacco companies. The other authors report no conflicts.
- © 2015 American Heart Association, Inc.
- Grana R,
- Benowitz N,
- Glantz SA
- Biener L,
- Hargraves JL