Good news for Big Tobacco: E-cigs are a strong gateway for young adults to start smoking cigarettes

It is almost an article of faith in tobacco control that about 90 of adult smokers smoke their first cigarette before age 18 and that virtually no one starts smoking after age 26.  That is likely why all the studies on the gateway effect of e-cigarettes leading to smoking have been done with youth, where the evidence is strong and consistent.
 
Now a troubling new study shows that e-cigarettes have changed that. 
 
Brian Primack and colleagues recently published “Initiation of Traditional Cigarette Smoking after Electronic Cigarette Use among Tobacco-Naïve U.S. Young Adults” that shows that the odds of never-smoking young adults (age 18-30) who use e-cigarettes having started to smoke cigarettes 18 months later at 6.8 times higher than young adults who don’t use e-cigarettes even after adjusting for a wide range of other factors that predict smoking.
 
This is a stunning result.  They found that 47.7% of never-smoking young adults who used e-cigarettes at baseline were smoking cigarettes a year later compared to just 10.2% of non-users.
 
While they did not explore why this happens in their survey, they make a pretty plausible argument in the Discussion section of their paper:
 

It may seem unlikely that e-cigarette users may transition from a flavored, highly palatable device such as an e-cigarette to a more noxious, unflavored cigarette. However, there are several reasons why individuals who try e-cigarettes may be at risk for this transition, even if they do not intend on smoking cigarettes at first. One reason is that many e-cigarettes—particularly early-generation devices—provide nicotine more slowly than traditional cigarettes. Thus, they may serve as an ideal transition vehicle, allowing a new user to advance to cigarette smoking as tolerance to side effects develops. Just as new cigarette users begin to report craving for nicotine within weeks of their first cigarette, initial e-cigarette users may soon begin to seek out cigarettes as a more efficient nicotine delivery device. E-cigarettes also mimic many powerful behavioral cues of cigarette smoking, including inhalation, exhalation, and holding the implement. For example, people exposed to e-cigarette advertising report more craving for smoking cigarettes. Initial exposure to nicotine in other forms—such as smokeless tobacco—can lead to later traditional cigarette smoking. Thus, one might expect susceptibility to be even greater when the presence of nicotine is augmented by strong behavioral cues of cigarette smoking. Finally, initial e-cigarette users also may transition to traditional cigarettes because of changing social pressures over time. For example, while most initial alcohol users favor sweet, sugary beverages, many ultimately transition to harsher and more concentrated forms. Future qualitative research among e-cigarette users may be particularly valuable for identifying whether this situation may be somewhat analogous for the transition from e-cigarettes to cigarettes.  [citations removed]

 
This is all bad news for public health and great news for the cigarette companies that are increasingly dominating the e-cigarette market.  The tobacco companies have worked for decades to crack the young adult market and e-cigarettes are the path.
 
Here is the abstract:
 

Background.  While electronic cigarettes (e-cigarettes) may help some smokers quit, some young adult never-smokers are now using e-cigarettes recreationally, potentially increasing their risk for initiation of smoking. We aimed to determine the association between baseline e-cigarette use and subsequent initiation of cigarette smoking among initially never-smoking young adults.
Methods.  We conducted a prospective cohort study with assessments at baseline (March 2013) and follow-up (October 2014). We used sampling frames representing 97% of the U.S. population to recruit a nationally-representative sample of never-smoking young adults ages 18-30. The independent variable was baseline ever use of e-cigarettes. The main outcome measure was initiation of traditional cigarette smoking between baseline and 18-month follow-up.
Results.  Baseline surveys were completed by 1506 never-smoking young adults, of whom 915 (60.8%) completed follow-up. There were no demographic differences between responders and non-responders. After applying survey weights—which accounted for both non-response and over or under coverage—2.5% of the represented population of never-smokers (801,010 of 32,040,393) used e-cigarettes at baseline. Cigarette smoking was initiated by 47.7% of e-cigarette users and 10.2% of non-users (P=.001). In fully-adjusted multivariable models, e-cigarette use at baseline was independently associated with initiation of smoking at 18 months (adjusted odds ratio=6.8, 95% confidence interval=1.7–28.3). Results remained similar in magnitude and statistically significant in all sensitivity analyses.
Conclusions.  Baseline e-cigarette use was independently associated with initiation of traditional cigarette smoking at 18 months. This finding supports policy and educational interventions designed to decrease use of e-cigarettes among non-smokers.

 
The full citation is  Primack B, et al.  Initiation of Traditional Cigarette Smoking after Electronic Cigarette Use among Tobacco-Naïve U.S. Young Adults.  Am J Med. 2017 Nov 17. pii: S0002-9343(17)31185-3. doi: 10.1016/j.amjmed.2017.11.005. [Epub ahead of print] 
 
The paper is available here.