Are e-cigarettes a gateway product that lead more people, especially teens, to smoke regular cigarettes?
No, according to public health researchers from the University at Buffalo and the University of Michigan writing in the journal Drug and Alcohol Dependence.
"The national trends in vaping and cigarette smoking do not support the argument that vaping is leading to smoking," said Lynn Kozlowski, the paper's lead author and a professor of community health and health behavior in UB's School of Public Health and Health Professions.
Kozlowski's co-author is Kenneth Warner, the Avedis Donabedian Distinguished University Professor of Public Health in Michigan's School of Public Health. Both Kozlowski and Warner are also former deans of their respective public health schools.
"Our analysis focused on the risks for moving from e-cigarettes to cigarettes. There is little evidence that those who have never smoked cigarettes or never used other tobacco products and first try e-cigarettes will later move on to cigarette usage with great frequency or daily, regular smoking," said Kozlowski.
Their paper highlights several shortcomings in studies that appear to show a link between e-cigarette use and subsequent smoking.
For example, many studies use misleading measures for what is actually considered smoking. "Measures of 'at least one puff in the past six months' can mean little more than the experimenting vaper was curious how cigarettes compared," Kozlowski said.
Warner added that in one study, only four e-cigarette users who previously hadn't smoked reported smoking cigarettes when measured again at a later time. "All of them said they'd smoked only one or two cigarettes in the past 12 months," Warner said. "None of the studies was designed to be able to follow up smoking intensity at a later date."
E-cigarette flavorings are another important consideration, because many young people report vaping with only flavorings -- no nicotine. Kozlowski and Warner pointed to a 2015 national survey of eighth- through 12th-grade students conducted by the University of Michigan's Monitoring the Future, an ongoing study of the behaviors, attitudes and values of American students and young adults and funded by the National Institute on Drug Abuse. The results showed that only 20 percent of the students surveyed who had used an e-cigarette reported that it contained nicotine.
Major national studies also have failed to control for most other tobacco use, including smokeless tobacco, and few have paid sufficient attention to confounding issues such as other alcohol and drug use and mental health issues, the researchers say. Youth who are experimenting with other substances are more likely to also try e-cigarettes or combustible cigarettes, according to the researchers.
"The evidence from the prospective studies is weak at best," Warner said. "All that it demonstrates is that there is a connection between kids who vape and future experimentation with smoking. But we know that these kids are different from those who do not vape. Even if there is a small gateway effect, it is totally swamped by the overall trend toward less and less smoking," Warner adds.
For next steps, Kozlowski and Warner say that regulations are needed to minimize product risks. "The public deserves accurate information on the health risks of e-cigarettes versus cigarettes," Kozlowski said. "From the best evidence to date, e-cigarettes are much less dangerous than cigarettes. The public has become confused about this."
Adds Warner: "The persistent focus on the potential risks to kids has caused adults' understanding of the risks of e-cigarettes to worsen over time. This is likely discouraging adult smokers from using e-cigarettes as a smoking cessation tool."