Association between e-cigarette use and future combustible cigarette use: Evidence from a prospective cohort of youth and young adults, 2017–2019

Highlights

• Young people who use e-cigarettes are more likely to smoke than those who do not.

• Modern vape devices do not decrease the risk of transition to combustible tobacco.

• JUUL use has similar risk of transition to combustible as use of non-JUUL devices.

• Young vapers were more likely than older vapers to continue vaping one year later.

Abstract

Introduction

A surge in popularity of e-cigarettes prompts concern given the association between e-cigarettes and future cigarette use. However, much of the evidence for this association comes from early, less efficient, and lower nicotine e-cigarettes than are available and widely used now. The goal of this study was to examine the relationship between e-cigarette use in 2018 and subsequent smoking initiation and continued e-cigarette use.

Methods

Participants included members of a national longitudinal panel of youth and young adults aged 15–27 who, in 2017, reported never having used a nicotine containing product (n = 3360). Logistic regression analyses assessed associations between participants’ self-reported ever e-cigarette use in 2018 and ever cigarette use, current cigarette use, and current e-cigarette use in 2019, after controlling for demographic and psychosocial variables.

Results

Compared with those who still had never used an e-cigarette, those who reported ever e-cigarette use in 2018 had significantly higher odds of ever cigarette use (aOR = 7.29, 95% CI [4.10, 12.97]), current cigarette use (aOR = 8.26, 95% CI [3.17, 21.53]), and current e-cigarette use (aOR = 9.70, 95% CI [6.41, 14.69]) one year later in 2019.

Conclusions

These findings show that the pod mod style, high nicotine containing e-cigarettes subject young users to the same risks of transitioning to combustible cigarettes as their earlier, less efficient predecessors. Strong regulation of all nicotine products, including e-cigarettes, is needed to prevent the trajectory of e-cigarette to cigarette use among youth and young adults.

Introduction

In recent years, electronic cigarette (e-cigarette) use has increased considerably among youth and young adults in the United States (US). Data from the National Youth Tobacco Survey (NYTS) indicate that in 2019, 27.5% of high school students were current e-cigarette users, an increase of 135% from 2017 (Campaign for Tobacco-Free Kids, 2019, Cullen et al., 2019). Similarly, the 2018 National Health Interview Survey (NHIS) data indicate that 7.6% of young adults ages 18–24 were current e-cigarette users, a 46% increase from the previous year (Dai & Leventhal, 2019).

The surge in e-cigarette use among youth and young adults prompted the US Surgeon General to declare youth e-cigarette use a national epidemic in December 2018, identifying that most e-cigarettes contain nicotine, a highly addictive chemical that can harm adolescent brain development (Surgeon General Releases Advisory on E-Cigarette Epidemic Among Youth, 2018). E-cigarettes are also known to emit harmful substances including fine particulate matter and metals, which have been linked to adverse health effects such as cardiovascular and respiratory illnesses (National Academies of Sciences - Engineering - and Medicine, 2018).

The increase in popularity of e-cigarettes among youth and young adults has also caused concern that e-cigarette use may serve to reduce risk perceptions of smoking or normalize smoking behaviors, potentially facilitating transitions to established use of combustible cigarettes (Barrington-Trimis et al., 2015, Barrington-Trimis et al., 2016, Schneider and Diehl, 2016). Evidence suggests that youth who use e-cigarettes perceive cigarette smoking to be less addictive and less harmful than do non-users (Owotomo, Maslowsky, & Loukas, 2018). Additionally, several recent cross-sectional and longitudinal studies demonstrate a significant association between e-cigarette use and future smoking initiation (National Academies of Sciences - Engineering - and Medicine, 2018). For example, a meta-analysis of nine longitudinal studies published between 2015 and 2017 found that among adolescents and young adults, ever use of e-cigarettes was associated with 3.6 times higher odds of cigarette smoking initiation at follow-up (Soneji, Barrington-Trimis, & Wills, 2017). Longitudinal cohort studies using nationally representative data have similarly found that youth e-cigarette use is significantly associated with increased risk for cigarette initiation and continued use (Berry et al., 2019, Chaffee et al., 2018, Stanton et al., 2019, Watkins et al., 2018).

While positive associations between e-cigarette use and cigarette use have been consistently found across observational contexts, these studies generally use older baseline data (usually from 2013 to 2014), and do not reflect the ever-changing e-cigarette product market. Since their emergence on the market in the early 2000s, there have been four “generations” of e-cigarette devices. Compared to traditional cigarettes, early e-cigarette devices were inefficient in delivering nicotine, thus presenting users with great risk of continuing or transitioning to combustible cigarette use (Glantz & Bareham, 2018).

Advances in e-cigarette design over the past decade have resulted in improved efficiency in nicotine delivery, resulting in greater maximum blood concentrations of nicotine and greater perceived nicotine effect to users of these products compared to first-generation e-cigarette models (Yingst, Foulds, & Veldheer, 2019). Until 2015, combustible cigarettes remained a more efficient nicotine delivery mechanism than any e-cigarette device (Yingst et al., 2019), although some e-cigarettes showed the potential to produce nicotine delivery profiles resembling combustible cigarettes (Lopez et al., 2016, Ramoa et al., 2016). In 2015, a fourth generation of e-cigarettes, known as “pod mods,” entered the market. Pod mod sales rose exponentially starting in 2017, growing from 26% of e-cigarette retail sales in the autumn of 2017 to 85% by the same point in 2019 (Total Nominal Sales Dollars from retail xAOC and C-Store Nielsen Retail Data, 2019, Huang et al., 2019). The recent steep increase in the prevalence of e-cigarette use among youth and young adults has been attributed to these products (Cullen et al., 2018, Cullen et al., 2019, Galstyan et al., 2019). These devices, such as the popular e-cigarette JUUL, are low-powered, have high nicotine concentrations, can be used discreetly, and come in flavors that appeal to youth (Cullen et al., 2018). In addition, pod mods use nicotine salts, which allow for high levels of nicotine to be inhaled easily and with less irritation (Surgeon General Releases Advisory on E-Cigarette Epidemic Among Youth, 2018). Nicotine yields of machine-tested JUUL devices reveal slightly higher levels than combustible cigarettes (Talih, Salman, & El-Hage, 2019). A recent study of adolescent pod mod users found urinary cotinine concentration (a biomarker of nicotine exposure) to be higher than the typical range found in studies of youth smokers of combustible cigarettes (Goniewicz, Boykan, Messina, Eliscu, & Tolentino, 2019). Early evidence indicates that youth who used e-cigarette products with higher nicotine concentrations progress to more frequent and intensive use of e-cigarettes and cigarettes over time (Goldenson et al., 2017, Kinnunen et al., 2019); these population-level findings precede the proliferation of pod mod use among youth.

Research is needed to determine whether youth who use e-cigarettes with high-nicotine content, such as JUUL, continue to use these products, or transition to use combustible cigarettes. In the current study, we use longitudinal data from 2017 to 2019 to examine whether e-cigarette use is predictive of continued e-cigarette use or combustible cigarette use among a national sample of previously nicotine naïve youth and young adults. Determining the likelihood of continued use of e-cigarettes or the use of combustible cigarettes among those who report no prior nicotine exposure can help inform youth tobacco prevention and cessation efforts as well as e-cigarette regulatory and legislative decisions.