In their study, researchers found almost 70% of individuals aged 16-24 who used e-cigarettes progressed to conventional cigarette use within a year.
Lead author Dr. Brian A. Primack, of the University of Pittsburgh School of Medicine, PA, and colleagues reached their findings by analyzing the survey results of a national sample of 694 individuals aged 16-26 who had never smoked conventional cigarettes.
Between 2012 and 2013, participants were required to complete a survey detailing their use of electronic cigarettes (e-cigarettes) and whether they were likely to use conventional cigarettes over the next year.
According to the researchers, all participants were deemed "non-susceptible" to initiating conventional smoking because they answered "definitely no" when asked if they were likely to take up the habit in the next year or if they would try a cigarette that was offered by a friend.
Participants' uptake of conventional smoking was assessed 1 year later.
Almost 70% of e-cigarette users progressed to conventional cigarette use
At the beginning of the study, 16 participants reported using e-cigarettes, while 678 said they did not use the devices.
After the 1-year follow-up, the researchers found that 11 of the 16 e-cigarette users (68.9%) had taken up smoking, compared with 128 of 678 participants (18.9%) who did not use e-cigarettes at study baseline.
The team says these results remained even after accounting for potential risk factors for tobacco use, such as age, sex, race, ethnicity, socioeconomic status, sensation seeking, parental smoking status and friends' smoking status.
While they admit a key limitation of the study is the small number of participants who reported e-cigarette use at study baseline, the researchers believe the findings have implications for regulation of the devices and warrant further investigation.
Study co-author Dr. James D. Sargent, professor of pediatrics at the Geisel School of Medicine at the Dartmouth-Hitchcock Norris Cotton Cancer Center in Lebanon, NH, adds:
"[...] Recent data suggest that more youth than ever are using e-cigarettes and that as many as half of these adolescents are not smoking traditional cigarettes.
Therefore, it is important to continue surveillance of both e-cigarettes and tobacco products among young people so policymakers can establish research-informed regulations to help prevent e-cigarettes from becoming gateway products on the road to youth smoking."
How might e-cigarette use lead to conventional smoking?
While the team is unable to determine exactly why e-cigarettes may act as a gateway to traditional cigarette use, they have some theories.
They note that e-cigarettes deliver nicotine more slowly than standard cigarettes, meaning a user may progress to conventional smoking as they become more tolerant of the substance's side effects.
- There are currently more than 250 different e-cigarette brands on the market in the US
- Though e-cigarettes are often promoted as being safer than conventional cigarettes, there is still limited evidence on the health risks of the devices
- Earlier this year, a report from the Centers for Disease Control and Prevention (CDC) found e-cigarette use tripled among middle and high school students in 2013-14.
They also point out that because e-cigarettes are designed to simulate the behavioral and sensory characteristics of conventional cigarette smoking, the user may become familiarized with the act of smoking.
Finally, the researchers say that because e-cigarettes are not regulated in the same way as conventional cigarettes, the devices may be "renormalizing" the act of smoking, hampering ongoing public health efforts to deter people from the habit.
The team notes that the regulation of e-cigarettes is controversial because many people use the devices to quit conventional smoking. However, they believe their findings add to increasing evidence suggesting e-cigarettes may have the opposite effect for teenagers and young adults.
In an editorial linked to the study, Dr. Jonathan D. Klein, of the American Academy of Pediatrics (AAP), says this latest data provides "strong longitudinal evidence that e-cigarette use leads to smoking, most likely owning to nicotine addiction."
"We do not need more research on this question; we have the evidence base, and we have strategies that work to protect nonsmokers from e-cigarettes and other forms of tobacco," he adds. "What we still need is the political will to act on the evidence and protect our youth."
Medical News Today recently reported on another study that raises concern about e-cigarette use among adolescents. In the journal Pediatrics, researchers reveal almost a fifth of high school students use e-cigarettes to vaporize cannabis instead of nicotine.