Analyzing the U.S. Public Health Impact of E-Cigarette Use in Adults and Adolescents

By Lina Sorg

In recent years, advertising campaigns, epidemiological studies, and governmental regulation about the negative effects of nicotine and tobacco have inspired a robust market for cigarette cessation products. One such product is electronic cigarettes (e-cigarettes) — discrete, battery-powered devices that emit doses of vaporized nicotine for inhalation. Companies like Juul promote e-cigarettes as a safer, healthier alternative to traditional cigarettes. Yet although they contain fewer hazardous chemicals, e-cigarettes still emit substantial quantities of nicotine and contain known carcinogens. Because e-cigarettes are so new, the long-term impacts on individual and public health are largely unknown. 

Since the introduction of e-cigarettes to the U.S. market in 2007, vaping has surged in both adults and adolescents. The U.S. government and health professionals are concerned about e-cigarettes’ appeal to young nonsmokers, especially because unique vape flavors, targeted advertisements (see Figure 1), low impulse control, and peer pressure disproportionately attract youth populations. Research indicates that nicotine negatively affects brain activity and stimulates an unnatural secretion of chemical signals that leads to desensitization, heightened nicotine tolerance, and ultimate dependence — particularly in adolescents with developing brains.

Existing studies about smoking and/or vaping examine prevalence from a descriptive or statistical viewpoint, but neither approach can predict future consumption. Knowledge of this subject would aid future government regulation of nicotine-emitting products. During a minisymposium presentation at the 2021 SIAM Conference on Applications of Dynamical Systems, which is taking place virtually this week, Lucia Wagner of St. Olaf College presented a dynamical model that predicts the future prevalence of traditional cigarette and e-cigarette consumption in both adult and adolescent U.S. users. 

Wagner’s model targets three urgent questions:

1. How did the introduction of e-cigarettes influence the prevalence of smoking?
2. What is the projected number of smokers who were diverted after the introduction of vaping?
3. From a public health perspective, do e-cigarettes present a net benefit or cost to society overtime?

Because social cues highly influence smoking and vaping habits, Wagner framed her model in the context of social group competition. Social group competition models examine factions in society that compete for members. Her model tracks the transitions between three discrete, competing groups: individuals who (i) primarily smoke traditional cigarettes, (ii) primarily vape e-cigarettes, and (ii) primarily abstain from all tobacco products (see Figure 2). Wagner assumes that the probability of transition depends on both the intrinsic utilities (physiological response, addiction, monetary cost, and the understanding of negative health risk) and social utilities (a sense of belonging, social production, and conformity). She derives the group’s total utility from these two qualities.

Figure 3 illustrates the relevant prevalence for smoking and vaping among U.S. adults and adolescents. When fitting the model, Wagner assumed that the tipping point—the year of maximum change in utility—for adult smokers was 1962: when the Royal College of Physicians directly communicated that cigarettes cause lung cancer (the U.S. Surgeon General followed suit soon after). For the youth population, she assumed that the tipping point occurred in 1995: when the U.S. Food and Drug Administration officially declared nicotine a drug.

Wagner extracted the model’s best-fit parameters by minimizing the error between the model and data via the Nelder-Mead algorithm. The model agrees with the Centers for Disease Control and Prevention’s (CDC) prevalence data that peak traditional cigarette consumption among adults took place in 1965, with a prevalence of 38.7 percent. It projects that peak e-cigarette use among adults will take place in 2050, with a prevalence of 19.3 percent.

The counterfactual model projection estimates that adult consumption of traditional cigarettes would be significantly higher if vaping was never introduced as a viable alternative. The model indicates that the average yearly prevalence of adult smokers who will be diverted by vaping between 2010 (the year the CDC began tracking e-cigarette use in adults) to 2030 is roughly 0.35 percent. Though this number seems small, it equates to 120,000 people per year who transition from traditional cigarettes and either abstain or turn to vaping; the latter is more likely. “Counterfactual model projection estimates that the introduction of e-cigarettes into the U.S. market heavily influenced and continues to influence traditional cigarette consumption among adults,” Wagner said. “This confirms previous studies that adults use vaping products as a method of smoking cessation.”

Wagner then turned to adolescents. Her model approximates that peak traditional cigarette consumption among youths occurred in 1996, with a prevalence of 34.9 percent. Peak e-cigarette use is forecasted for 2024, with a prevalence of 51.7 percent. From 2011 (the year the CDC began tracking e-cigarette use in high schoolers) to 2030, the average yearly prevalence of adolescent smokers who will be diverted by vaping is roughly 0.39 percent. Therefore, nearly 58,000 adolescents per year will transition out of the cigarette group due to vaping. As with the adult population, vaping clearly impacts the prevalence of smoking in adolescents. However, the literature suggests that the lure of e-cigarettes among youths is spurred more by social norms and less by the appeal of a healthier lifestyle.

Assuming that her model projections resemble reality, Wagner estimated the net public health benefit or harm caused by introduction of e-cigarettes into the U.S. market. This assessment depends on two factors: (i) the number of e-cigarette users who were former smokers versus former abstainers, and (ii) the relative health risks of smoking and vaping. One can define the net public health ratio of nicotine products at any given time. The ratio \(R\) determines how much riskier (in terms of health risk) smoking must be for vaping to have a net public health benefit to society. For example, Wagner’s model suggests that if the health risk of smoking is 1.8 times worse than vaping in 2030, e-cigarettes will pose a net benefit for public health in adult populations. For adolescent populations, e-cigarettes will present a net benefit for public health in 2030 if the health risk of smoking is four times worse than vaping. The model can account for any ratio \(R\) to determine whether vaping would present as a net loss or a net gain at any given time.

Ultimately, Wagner’s model effectively estimates long-term behavior of traditional cigarette and e-cigarette consumption in U.S. society. “The introduction of vaping products heavily influences the usage of traditional cigarettes among both adults and adolescents,” Wagner said. “Our work has ample implications within the public health sector, recognizing that rising projections of vaping prevalence among adolescents ought to aid in governmental regulations and public policy measures.”

Lina Sorg is the managing editor of SIAM News.