Teens using e-cigarettes 6x more likely to transition to smoking conventional cigarettes.
Teens using e-cigarettes were six times more likely to transition to smoking conventional cigarettes in early adulthood than those who never "vaped," according to researchers.
In the analysis of data from a large, prospectively followed cohort of high school-age children in Southern California, e-cigarette users had 6.17 times the odds (95% CI 3.30-11.6) of becoming cigarette smokers compared with never users of e-cigarettes, reported Jessica Barrington-Trimis, PhD, of the University of Southern California Keck School of Medicine in Los Angeles, and colleagues.
In addition, 36% of teen (mean age 17.4) vapers who reported little desire to use traditional tobacco products at an initial interview later reported that they were smoking cigarettes, suggesting that e-cigarette uptake is not just occurring among adolescents who would have smoked anyway, they wrote in Pediatrics.
The findings add to the evidence that e-cigarette use may have a gateway effect among teens who are too young to purchase cigarettes legally, increasing the likelihood that they will become cigarette smokers in adulthood, the authors stated.
E-cigarette use among teens has risen dramatically as use of traditional cigarette has fallen to the lowest levels since the government started tracking teen tobacco use in 1991.
In a 2015 survey of more than 15,000 U.S. high school students reported this week by the CDC, 24% said they used e-cigarettes during the past 30 days.
Several recent studies suggest that e-cigarette users have different psychological profiles than traditional smokers, the researchers noted.
"Together, these findings suggest that e-cigarettes are not merely a marker for individuals who would have gone on to smoke combustible cigarettes, regardless of the availability of e-cigarettes, but that e-cigarette use is likely introducing new youth to tobacco products and is increasing the likelihood of future smoking among the low-risk group who expressed confidence that they would not do so," they wrote.
The researchers evaluated data from the ongoing Southern California Children's Health Study, which is prospectively following children through adolescence into adulthood.
Data on e-cigarette use were first collected in grades 11 or 12 in the spring of 2014, to examine risk of initiation of combustible tobacco products at follow-up, which was, on average, 16 months later.
The analysis included 146 11th and 12th graders who reported never smoking cigarettes, but were using e-cigarettes at initial evaluation, and 11th and 12th graders matched to e-cigarette users who reported never smoking neither e-cigarettes nor cigarettes.
Cigarette initiation during follow-up was reported by 40.4% of e-cigarette users and 10.5% of never users.
Those who were classified as susceptible to cigarettes based on initial interview responses were most likely to report e-cigarette use at the initial interview (odds ratio 2.48, 95% CI 1.44-4.27) and to report cigarette use at follow-up (OR 3.03, 95% CI 1.71-5.39).
Among teens not classified as susceptible to cigarette use at initial evaluation, 36.2% of e-cigarette users and 5.7% of never e-cigarette users reported initiation of cigarettes at follow-up (not susceptible OR=9.69, 95% CI 4.02-23.4). Among those classified as susceptible to smoking at initial interview, e-cigarette users were only slightly more likely to initiate cigarette use at follow-up (susceptible OR= 2.12, 95% CI 0.79-5.74).
The authors also reported that e-cigarette users were also more likely to initiate use of any combustible product (OR=4.98, 95% CI 2.37–10.4), including hookah, cigars, or pipes.
Study limitations included the small sample size and relatively short follow-up time.
The authors pointed out that "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."
They concluded that more research is needed to further define the impact of e-cigarette use in adolescence on smoking initiation.
Tobacco cessation specialist Amy V. Lukowski, PsyD, of National Jewish Health in Denver said the study bolsters the evidence linking early vaping to cigarette smoking.
"Because they are so new, we haven't really known much about the impact of e-cigarette use on combustible cigarette use until recently," said Lukowski, who was not involved in the study. "But the evidence is growing, and the data support the fear that many of us in the public health community have had that e-cigarettes are a gateway product."
The study was funded by the National Cancer Institute and the FDA Center for Tobacco Products.
Barrington-Trimis and co-authors disclosed no relevant relationships with industry.
Reviewed by Henry A. Solomon, MD, FACP, FACC Clinical Associate Professor, Weill Cornell Medical College and Dorothy Caputo, MA, BSN, RN, Nurse Planner
Source Reference: Barrington-Trimis JL, et al "E-cigarette and future cigarette use" Pediatrics 2016; DOI: 10.1542/peds.2016-0379.