A review of: Sabeeh Baig and Daniel Giovenico, “Behavioral heterogeneity among cigarette and e-cigarette dual-users and associations with future tobacco use: Findings from the Population Assessment of Tobacco and Health Study,” Addictive Behaviors 104 (May 2020).

Reviewed by: Carrie Wade

In their 2018 report on the health effects of e-cigarettes, the National Academies of Science, Engineering and Medicine (NASEM) conclude that: “completely substituting e-cigarettes for combustible tobacco cigarettes reduces users’ exposure to numerous toxicants and carcinogens present in combustible tobacco cigarettes,” and that “there is substantial evidence that completely switching from regular use of combustible tobacco cigarettes to e-cigarettes results in reduced short-term adverse health outcomes in several organ systems.” Indeed, both the NASEM and Public Health England—two of the world’s leading public health bodies—agree that e-cigarettes can be beneficial to smokers who completely switch.

Unfortunately, however, the endorsement of e-cigarettes as a harm reduction tool for smokers does not currently extend to “dual users” (people who use both combustible and e-cigarettes as a source of nicotine). In some part, hesitation to acknowledge the harm reduction benefits to these users stems from the fact that currently, the concept of “dual use” is poorly defined and its use patterns are not well known. Accordingly, in an effort to explore the patterns of dual use and its temporal effects, a recent study examined the associations between dual-use behaviors and longitudinal outcomes related to complete switching to e-cigarettes and quitting tobacco and nicotine use entirely.

To assess the longitudinal outcomes of dual use, this study examined data from the Population Assessment on Tobacco and Health (PATH) Study, which evaluates individual tobacco-use characteristics on a yearly basis. In so doing, the authors followed 1,665 U.S. adults who used both e-cigarettes and combustible cigarettes for two years starting at Wave 1 (2013-2014) and then reevaluated the pattern of dual use at Wave 3 (2015-2016). Overall, it was found that, at Wave 1, nearly 70 percent of dual users were predominantly smokers, which is defined as smoking every day and vaping some days. By Wave 3, nearly 7 percent of dual users became exclusive vapers and 10 percent had quit all forms of tobacco use.

Closer examination of the data also revealed some important patterns. For example, compared to those who predominantly smoke, heavy dual users (those who use e-cigarettes and combustible cigarettes daily) and light dual users (those who use e-cigarettes and combustible cigarettes some days) were twice as likely to completely switch to vaping two years later. Further, people who mostly used e-cigarettes and smoked only occasionally at Wave 1 were six times as likely to completely switch to vaping by Wave 3, two years later. And, light dual users were 4 times more likely to completely stop smoking and vaping at Wave 3 than those who predominantly smoke. Such data suggests that, over time, e-cigarettes are most likely to act as a gateway out of combustible use for those who use e-cigarettes and combustible cigarettes equally. And, for those who favor e-cigarettes, they may act as a gateway out of both combustible use and nicotine use altogether.

Coupled with previous studies demonstrating the superiority of e-cigarettes to aid in smoking cessation compared to traditional quitting methods, these data provide additional support to the hypothesis that e-cigarettes act primarily as a gateway away from combustible use rather than toward it. Additionally, these data provide important evidence that, for most, dual use does not lead to increased dependence upon nicotine or combustible cigarettes.

Finally, Baig and Giovenico’s study builds upon previous work by including an examination of socioeconomic demographics that are known to be associated with smoking. And, in so doing, they find at least one important aspect of e-cigarettes that can be modified to increase successful complete switching. Compared to those at-or-below the poverty level, those who were above the poverty level were twice as likely to completely switch to e-cigarettes. This suggests that high price may be a barrier to use for many smokers, and this is especially important considering that those at-or-below the poverty level have higher rates of smoking and a higher burden of smoking-related diseases. For e-cigarettes to be as effective as possible as a harm reduction tool for those most vulnerable, then, they will have to be made more—rather than less—available, and more affordable.

One key aspect of the FDA’s comprehensive plan for the future of tobacco includes moving current and future smokers away from combustible cigarettes and toward safer forms of nicotine delivery. However, abrupt transition away from combustible cigarettes is highly unlikely, and thus these data confirm that dual use is a transitory state for many nicotine users—one that can lead them toward more successful quit rates—if the proper policies are adopted.