Kids are not just substituting e-cigs for cigs; e-cigs are expanding the tobacco epidemic

Jessica Barrington-Trimis and her colleagues have published two important papers in Pediatrics on the link between e-cigarette and cigarette use, both based on a large longitudinal sample of Southern California youth who have been followed for many years.
 
Their paper “E-cigarettes, Cigarettes, and the Prevalence of Adolescent Tobacco Use” showed that, contrary to assertions of e-cigarette cheerleaders, the large increase in e-cigarette use observed in several national studies in recent years are not simply reflecting kids taking up e-cigarettes instead of e-cigarettes.   While some kids who are using e-cigarettes are also smokers, kids are being attracted to e-cigarettes who would otherwise not be attracted to tobacco products. 
 
Here is the abstract:

BACKGROUND: Adolescent e-cigarette use has increased rapidly in recent years, but it is unclear whether e-cigarettes are merely substituting for cigarettes or whether e-cigarettes are being used by those who would not otherwise have smoked. To understand the role of e-cigarettes in overall tobacco product use, we examine prevalence rates from Southern California adolescents over 2 decades.
METHODS: The Children’s Health Study is a longitudinal study of cohorts reaching 12th grade in 1995, 1998, 2001, 2004, and 2014. Cohorts were enrolled from entire classrooms in schools in selected communities and followed prospectively through completion of secondary school. Analyses used data from grades 11 and 12 of each cohort (N = 5490).
RESULTS: Among 12th-grade students, the combined adjusted prevalence of current cigarette or e-cigarette use in 2014 was 13.7%. This was substantially greater than the 9.0% adjusted prevalence of current cigarette use in 2004, before e-cigarettes were available (P = .003) and only slightly less than the 14.7% adjusted prevalence of smoking in 2001 (P = .54). Similar patterns were observed for prevalence rates in 11th grade, for rates of ever use, and among both male and female adolescents and both Hispanic and Non-Hispanic White adolescents.
Smoking prevalence among Southern California adolescents has declined over 2 decades, but the high prevalence of combined e-cigarette or cigarette use in 2014, compared with historical Southern California smoking prevalence, suggests that e-cigarettes are not merely substituting for cigarettes and indicates that e-cigarette use is occurring in adolescents who would not otherwise have used tobacco products. [emphasis added]

Their second paper, “E-Cigarettes and Future Cigarette Use,” also in Pediatrics, showed that never-smoking kids in the same cohort who start using tobacco products with e-cigarettes had 6.17 times the odds of smoking cigarettes 16 months later than kids who did not use e-cigarettes, adding to the growing consistent evidence that e-cigarettes are a gateway to cigarette smoking.  (Of course, having kids inhaling a mixture of hot propylene glycol, nicotine, and other stuff is not a good thing, even if they didn’t go on to cigarettes.)
 
Here is the abstract:

BACKGROUND: There has been little research examining whether e-cigarette use increases the risk of cigarette initiation among adolescents in the transition to adulthood when the sale of cigarettes becomes legal.
METHODS: The Children’s Health Study is a prospectively followed cohort in Southern California. Data on e-cigarette use were collected in 11th and 12th grade (mean age = 17.4); follow-up data on tobacco product use were collected an average of 16 months later from never-smoking e-cigarette users at initial evaluation (n = 146) and from a sample of never-smoking, never e-cigarette users (n = 152) frequency matched to e-cigarette users on gender, ethnicity, and grade.
RESULTS: Cigarette initiation during follow-up was reported by 40.4% of e-cigarette users (n = 59) and 10.5% of never users (n = 16). E-cigarette users had 6.17 times (95% confidence interval: 3.30–11.6) the odds of initiating cigarettes as never e-cigarette users. Results were robust to adjustment for potential confounders and in analyses restricted to never users of any combustible tobacco product. Associations were stronger in adolescents with no intention of smoking at initial evaluation. E-cigarette users were also more likely to initiate use of any combustible product (odds ratio = 4.98; 95% confidence interval: 2.37–10.4), including hookah, cigars, or pipes.
CONCLUSIONS: E-cigarette use in never-smoking youth may increase risk of subsequent initiation of cigarettes and other combustible products during the transition to adulthood when the purchase of tobacco products becomes legal. Stronger associations in participants with no intention of smoking suggests that e-cigarette use was not simply a marker for individuals who would have gone on to smoke regardless of e-cigarette use. [emphasis added]

These two papers add to the case that e-cigarettes are extending and expanding the tobacco epidemic.
 
The full citations for the papers are
 
Jessica L. Barrington-Trimis, Robert Urman, Adam M. Leventhal, W. James Gauderman, Tess Boley Cruz, Tamika D. Gilreath, Steve Howland, Jennifer B. Unger, Kiros Berhane, Jonathan M. Samet, Rob McConnell.  E-cigarettes, Cigarettes, and the Prevalence of Adolescent Tobacco Use.  Pediatrics Published online July 11, 2016 doi: 10.1542/peds.2015-3983
 
Jessica L. Barrington-Trimis, Robert Urman, Kiros Berhane, Jennifer B. Unger, Tess Boley Cruz, Mary Ann Pentz, Jonathan M. Samet, Adam M. Leventhal, Rob McConnell.  E-Cigarettes and Future Cigarette Use.  Pediatrics 2016;138: e20160379 DOI: 10.1542/peds.2016-0379.  Published online July 01, 2016.