Prevalence and Distribution of E-Cigarette Use Among U.S. Adults: Behavioral Risk Factor Surveillance System, 2016

E-cigarettes were introduced in the United States more than a decade ago, with the general population perceiving these products as a safer substitute for combustible cigarettes (1). Subsequently, the prevalence of e-cigarette use has risen, especially among adolescents and younger adults (2). The medical community, however, remains concerned regarding both the safety of e-cigarettes and their utility as smoking cessation devices. In 2015, the American College of Physicians recommended that the U.S. Food and Drug Administration (FDA) provide regulatory oversight of e-cigarettes, citing the lack of conclusive data on their safety and effectiveness as a cessation aid and their potential as a gateway to use of other tobacco products with known harms (3). In 2016, the FDA finalized the Deeming Rule that extended its regulatory authority beyond cigarettes and smokeless and roll-your-own tobacco to all tobacco products, including e-cigarettes, cigars, hookahs, and pipes (4). Therefore, the deeming rule gives the FDA authority to regulate e-cigarettes and to place health warnings and age restrictions on their sales. Given the potential health concerns surrounding e-cigarettes, a detailed analysis of their contemporary use patterns takes on great importance. Although previous research from nationally representative data sets suggested rising e-cigarette prevalence, especially among younger adults, these studies are now outdated, and they were not sufficiently powered to report the prevalence of e-cigarette use among important subgroups (5, 6). Using the largest and most extensive dynamic health surveythe 2016 Behavioral Risk Factor Surveillance System (BRFSS) national surveywe aimed to determine the most up-to-date national and state-level prevalence of current e-cigarette use among U.S. adults. We also examined the prevalence of e-cigarette use among key demographic subgroups, which included stratification by cigarette smoking status. These data may help delineate the complex relationship between e-cigarette use patterns and demographic, socioeconomic, and geographic factors and help inform the work of researchers, public health officials, and regulatory authorities seeking to understand current trends in e-cigarette use. Methods Data Source The BRFSS is an extensive, nationally representative, health-related telephone panel survey conducted jointly by the Centers for Disease Control and Prevention (CDC) and all states and participating territories of the United States. In summary, data were collected by landline and cellular telephone from 486303 noninstitutionalized adults aged 18 years and older regarding risk behaviors, use of preventive services, and chronic health conditions (7). Study Population and E-Cigarette Use The BRFSS began collecting data on e-cigarette use in 2016. We included 466842 persons (96% of the entire survey population) who provided information about e-cigarette use. First, the participants were asked, Have you ever used an e-cigarette or other electronic vaping' product, even just one time, in your entire life? Those who answered yes were asked a second question: Do you now use e-cigarettes or other electronic vaping' products every day, some days, or not at all? We considered participants who answered yes to the first question as evere-cigarette users. Of evere-cigarette users, we defined daily and occasional e-cigarette use as responding every day and some days, respectively. We defined current e-cigarette use as either daily or occasional. In the assessment of prevalence estimates by subgroups, respondents with missing information on the subgroup of interest were excluded. Appendix Table 1 provides information on the size of the study population for each subgroup examined. The sexual orientation and gender identity questions were asked in the following 26 states and territories: California, Connecticut, Delaware, Georgia, Guam, Hawaii, Idaho, Illinois, Indiana, Iowa, Kentucky, Louisiana, Massachusetts, Minnesota, Mississippi, Missouri, Nevada, New York, Ohio, Pennsylvania, Rhode Island, Texas, Vermont, Virginia, Washington, and Wisconsin. Response rates in the states that included these modules were 87.4% (sexual orientation) and 86.3% (gender identity). Appendix Table 1. Study Population for the Whole Population and Each Subgroup, 2016 Behavioral Risk Factor Surveillance System* Combustible Cigarette Smoking Participants who answered yes to Have you smoked at least 100 cigarettes in your entire life? were considered evercigarette smokers, whereas those who answered no were considered nevercigarette smokers. Of evercigarette smokers, a second question was asked: Do you now smoke cigarettes every day, some days, or not at all? Participants who answered every day or some days were defined as current cigarette smokers, and those who answered not at all were defined as former cigarette smokers. Other Study Measures Key socioeconomic covariates of our analyses included age, sex (male or female), sexual orientation (heterosexual, lesbian, gay, or bisexual), gender identity (cisgender or transgender), race/ethnicity, educational attainment, relationship status (with partner or without partner), pregnancy, and employment. Household income was reported according to the federal poverty line in 2016 (8). Body mass index was calculated on the basis of self-reported height and weight. Information about lifestyle factors included physical activity (at least 1 exercise session during the past 30 days) and alcohol intake (at least 1 alcoholic drink during the past 30 days). Chronic health conditions included cardiovascular disease, diabetes, cancer (excluding skin cancer), chronic obstructive pulmonary disease, depression, and chronic kidney disease. Participants with cardiovascular disease were defined as those who reported having myocardial infarction, coronary heart disease, or stroke. All variables were self-reported. For categorization of responses, we used BRFSS-defined criteria (9). Weighting Process In 2016, 50 states, the District of Columbia, Guam, Puerto Rico, and the U.S. Virgin Islands collected data via landline and cellular telephone. The BRFSS uses a weighting methodology called raking that allows incorporation of landline and cellular telephone survey data and permits the introduction of additional characteristics that improve the degree to which the BRFSS sample accurately reflects the sociodemographic make-up of the United States as well as the individual states. More details on study design, sampling, data collection, and weighting processes are published elsewhere (10). Statistical Analysis We calculated the weighted and direct age-standardized prevalence estimates using BRFSS analytic recommendations published by the CDC (10, 11). Direct age standardization was based on the standard 2000 U.S. Census population using age categories of 18 to 44 years, 45 to 64 years, and 65 years or older. Furthermore, we age standardized the prevalence estimates in each subgroup to account for differences in the age composition of the subgroups. We tested for a linear trend in prevalence of e-cigarette use across 5-year age groups by using logistic regression with age group included as a continuous variable. We compared the prevalence of e-cigarette use by socioeconomic and lifestyle covariates, and chronic health conditions by using logistic regression models adjusted for age group. From these models, we found age-adjusted prevalence values (predicted margins), and we report results as absolute prevalence difference, with 95% CIs. Because of the likely interaction between e-cigarette use and cigarette smoking, as well as the high prevalence of dual use (12), analyses were repeated after stratification by combustible cigarette smoking status (never, former, or current). We estimated the number of e-cigarette users in the United States by applying the nationally representative prevalence estimates to the U.S. Census projection of the number of adults in 2016 (13). All analyses were performed by using Stata, version 13.1 (StataCorp), and used BRFSS weights to account for the complex survey design, noncoverage, and nonresponse. We used the svy command in Stata to account for the complex design of BRFSS; the tab command to obtain direct age-standardized, weighted prevalence estimates; and the logistic command in conjunction with margins, nclom, and test postestimation commands to obtain predictive margins and prevalence difference with 95% CIs and P values (14). Role of the Funding Source This study was funded by the American Heart Association Tobacco Regulation and Addiction Center (A-TRAC), which is one of the Tobacco Centers of Regulatory Science of the FDA and National Heart, Lung, and Blood Institute. The funder had no role in study design, conduct, data collection, trial management, data analysis, manuscript preparation, or the decision to submit the manuscript for publication. Results Prevalence of E-Cigarette Use Among All U.S. Adults The overall prevalence of current e-cigarette use was 4.5% (95% CI, 4.4% to 4.6%). Among current users, 33.5% used e-cigarettes daily. Translating these results to the entire U.S. adult population, the estimated number of current e-cigarette users was 10.8 million (3.6 million daily users). Patterns of E-Cigarette Use Across Age Groups The median age category of current e-cigarette users was younger than that of nonusers (40 to 44 vs. 55 to 59 years, respectively [P < 0.001]). As shown in Figure 1, the prevalence of current and daily e-cigarette use decreased with increasing age. Across age groups, the prevalence of current e-cigarette use was highest among those aged 18 to 24 years (9.2% [CI, 8.6% to 9.8%]). More than half (51.2%) of all e-cigarette users were younger than 35 years. Figure 1. Prevalence of e-cigarette use among U.S. adults, according to age group, 2016 Behavioral Risk Factor Surveillance System survey. P values for trends <0.001. Error bars represe