Vaping might increase the risk of becoming a conventional smoker among teenagers.
Contrary to popular belief, e-cigarettes (electronic cigarettes) contain a variety of chemicals also found in normal cigarettes, which have been proven to be harmful and have been associated with cancer.
The Food and Drug Administration (FDA) have pointed out that e-cigarettes contain "detectable levels of known carcinogens and toxic chemicals to which users could be exposed."
But e-cigarettes have also been associated with regular smoking, and many smokers use vaping to help them quit smoking conventional cigarettes.
A recent study examines the link between the use of e-cigarettes and subsequent smoking of "normal," combustible cigarettes among adolescents.
Thirty-seven percent of 10th-grade American teenagers reportedly use e-cigarettes.
Although vaping in early adolescence has been previously associated with starting to smoke combustible cigarettes, whether vapers progress to heavier or more frequent smoking was unknown.
The new study looks at the association between vaping and subsequent frequency and heaviness in the use of conventional cigarettes.
Studying the link between vaping and smoking in teens
The study was led by Adam M. Leventhal, Ph.D., of the University of Southern California Keck School of Medicine, and it was recently published in the journal JAMA.
The research consists of a meta-analysis of surveys administered to 10th graders across ten public high schools in Los Angeles, CA, during 2014-2015. The surveys were first administered at the beginning of the academic year in the fall, which made up the baseline of the study, and again in the spring for the follow-up.
In total, the study collected data from 3,282 respondents in autumn and 3,251 at follow-up.
Researchers devised a 4-level scale for assessing e-cigarette vaping in the fall: "never" for those who never vaped, "prior" for those who had vaped but not in the last 30 days, "infrequent" for respondents who had vaped 1 or 2 days during the past 30 days, and "frequent" for those who had vaped for 3 days or more.
For the follow-up, a similar scale was applied to assess the frequency of combustible cigarette smoking. Respondents had the options of nonsmoker, "infrequent smoker" for those who had smoked for 1 or 2 days in the 30 days before the study, and finally, "frequent smoker" for those who had smoked for at least 3 days.
The survey also included a variable for heaviness, with zero, less than one, one, and two or more cigarettes per day on smoking days.
Smoking increases proportionally with vaping
At follow-up, researchers found that the smoking frequency had risen proportionally with the vaping frequency; the more respondents had vaped in the fall, the more they smoked 6 months later.
Only 0.7 percent of never-vapers became frequent smokers, and 0.9 percent of never-vapers became infrequent cigarette smokers.
Of the prior-vapers, 4.1 percent became infrequent smokers, while 3.3 percent became frequent smokers.
Nine percent and 5.3 percent of infrequent vapers became infrequent smokers and frequent smokers, respectively.
Finally, a significant proportion of frequent vapers became infrequent or frequent smokers - namely 11.6 percent and 19.9 percent, respectively.
By contrast, 98.5 percent of those who had never vaped reported being a nonsmoker 6 months later.
The positive association between baseline vaping and follow-up smoking was much stronger among baseline nonsmokers; those who had not vaped at all were extremely unlikely to start smoking.
The same proportional trend was found in the heaviness of smoking; with each increment on the 4-level baseline scale, there were proportionally higher odds of smoking at greater frequency and heaviness.
Although some teenagers use vaping as an aid to stop smoking, this study did not register any associations with smoking reduction.
Why the link between vaping and smoking is significant
Among both adolescents and adults, the rates of first use of e-cigarettes have doubled from 2008 through 2012.
During this period, first ever use of e-cigarettes among middle school students in the United States increased from 1.4 percent to 2.7 percent.
Among high school students, first ever use increased from 4.7 percent to 10 percent.
As the authors of the study point out, there is a lot more to investigate, but given what we know so far, antismoking policies may need to consider e-cigarettes more seriously. Leventhal and team conclude:
"The role of nicotine and generalizability of these results to other locations and ages, longer follow-up periods, and non-self-report assessments are unknown and merit further inquiry. The transition from vaping to smoking may warrant particular attention in tobacco control policy."