Patterns and trends of dual use of e-cigarettes and cigarettes among U.S. adults, 2015-2018

Abstract

Introduction: If dual use of cigarettes and e-cigarettes is a transition state to tobacco and nicotine use cessation, it may be a tolerable temporary condition. But, if a long-term behavior, dual use may increase tobacco harm to the population as a whole, and efforts should aim to reduce it as much as possible. To develop effective tobacco control policy, the changes in dual use of e-cigarettes and cigarettes need to be better understood.

Methods: National probability samples of U.S. adults in 2015 (n = 6051), 2016 (n = 6014), 2017 (n = 5992), and 2018 (n = 5989) reported their smoking and e-cigarette use status, including frequency of use. Weighted multinomial logistic regression models were used to examine temporal trends and patterns of cigarette and e-cigarette use.

Results: Between 2015 and 2018, the prevalence of current e-cigarette use (29.8% in 2015, 22.3% in 2016, 29.1% in 2017, and 27.7% in 2018) did not change significantly among current smokers. This result was consistent among light, moderate, and heavy smokers, and did not change when stratified by sex, age and race. However, the prevalence of cigarette smoking in current e-cigarette users declined from 56.9% in 2015 to 40.8% in 2018 (p < 0.001). Among never (p = .012) and former (ps < 0.001) smokers the prevalence of current e-cigarette use increased significantly.

Conclusion: The continued high prevalence of dual use and increased prevalence of current e-cigarette use among never smokers highlight the need for better communication about the risks of prolonged dual use for e-cigarette users, and the risks of nicotine initiation and addiction for nonusers.

Fig. 1

Trends in prevalence of current e-cigarette use by smoking status. Note: All current smokers included light, moderate, and heavy smokers. Light smokers smoked 1–4 cigarettes per day, moderate smokers smoked 5–14 cigarettes per day and heavy smokers smoked > 14 cigarettes per day. Between 2015 and 2018, prevalence of current e-cigarette use increased significantly in never (p = .012) and former (p < .001) smokers. Quadratic trend was significant in never (p = .029) and former (p = .040) smokers. Cubic trend was significant in former smokers (p = .032) and moderate smokers (5–14 cigarettes per day) (p = .024).

Fig. 2

Trends in prevalence of current cigarette smoking by e-cigarette use. Note: There was a significant decrease in the prevalence of cigarette smoking in current e-cigarette users (p < 0.001). Quadratic trend was significant in former e-cigarette users (p = 0.010).

Fig. 3

Trends in prevalence of e-cigarette use by intentions to quit smoking. Note: Prevalence of current e-cigarette use did not decrease or increase from 2015 to 2018. Prevalence of current e-cigarette use showed significant quadratic trend in smokers who plan to quit someday but not in the next year (p = 0.013). Significant cubic trends in the prevalence of current e-cigarette use were seen among smokers who never plan to quit (p = 0.003) and smokers who plan to quit someday but not in the next year (p = 0.009).

Fig. 4

Trends in prevalence of 10 or more days of e-cigarettes use in the past 30 days among dual users. No significant trend was observed. Light smokers smoked 1–4 cigarettes per day, moderate smokers smoked 5–14 cigarettes per day, and heavy smokers smoked >14 cigarettes per day.