Abstract
This population epidemiology study uses 2014-2018 data from National Health Interview Surveys to assess trends in prevalence of current and daily e-cigarette use by US adults and to characterize trends by sociodemographic and smoking status among young adults (18-24 years).
Prevalence of e-cigarette use among US adolescents substantially increased from 2017 to 2018.1 Whether prevalence also increased among young adults (18-24 years)—a population with high vaping rates2 and vulnerability to nicotine dependence and other health consequences of nicotine exposure3—is unknown.
Prevalence of current e-cigarette use decreased among all US adults between 2014 and 2016.4 This study examined 2014-2018 trends and the 2017-2018 biannual change in prevalence of e-cigarette use in US adults of different ages. Among young adults, e-cigarette use trends by sociodemographic and smoking status were also examined.
Methods
Respondents were from 2014-2018 National Health Interview Surveys—annual cross-sectional household face-to-face interviews of nationally representative noninstitutionalized US civilian samples (household response rates, 64.2%-73.8%).5 The University of Nebraska institutional review board determined this study to be non–human subjects research.
Self-reported current e-cigarette use (yes vs no [never or former use]) and daily e-cigarette use (yes vs no [never, former, or nondaily current use]) were primary and secondary outcome variables, respectively. Year (2014-2018) and age (18-24, 25-44, 45-64, ≥65 years) were independent variables. Covariates were self-reported combustible cigarette smoking (never [<100 cigarettes smoked lifetime], former [smoked ≥100 cigarettes and not currently smoking], current [≥100 cigarettes and currently smoking]),2 sex, race/ethnicity, and poverty ratio (ratio of family income to federal poverty threshold).
Logistic regression tested linear and quadratic changes in prevalence of e-cigarette use across 2014-2018 and the biannual 2017-2018 change overall and stratified by age. Age × year interactions tested age differences in rate of change. Among young adults, we examined current e-cigarette use trends by year, stratified by demographic covariates and smoking status. Weighted estimates and 95% confidence intervals (CIs) with Taylor series variance estimation were generated in SAS version 9.4. P < .05 (2-tailed) was considered statistically significant.
Results
The pooled sample (N = 155 556) was 12.1% young adult, 51.8% women, 64.3% non-Hispanic white, 11.7% non-Hispanic black, and 15.8% Hispanic, including 11.3% with poverty ratio less than 1.0 and 22.1% former and 15.0% current cigarette smokers.
Overall prevalence of reported current e-cigarette use was 3.7% (2014), 3.5% (2015), 3.2% (2016), 2.8% (2017), and 3.2% (2018) and fit a significant quadratic trend over 2014-2018 (P = .03). Changes in current e-cigarette use from 2014-2018 and 2017-2018 differed by age (age × year P < .001 and P = .009, respectively). For young adults, reported current e-cigarette use exhibited a significant quadratic trend over 2014-2018 (5.1%, 5.2%, 4.7%, 5.2%, 7.6%) (Figure, panel A) and 2017-2018 biannual increase (difference, 2.4% [95% CI, 0.4%-4.4%]) (Figure, panel B). Reported e-cigarette use did not significantly change among adults aged 25 to 44 years and linearly decreased in those aged 45 to 64 years and 65 years and older over 2014-2018; 2017-2018 changes were nonsignificant in these groups. Similar results were observed for reported daily e-cigarette use, which significantly differed by age over 2014-2018 (P < .001) (Figure, panel C) and 2017-2018 (P = .01) (Figure, panel D).
Figure. Prevalence of e-Cigarette Use Among US Adults, 2014-2018, Stratified by Age (N = 155 556)a.
aWeighted estimates from National Health Interview Survey years 2014 (n = 36 697), 2015 (n = 33 672), 2016 (n = 33 028), 2017 (n = 26 742), 2018 (n = 25 417). Logistic regression was used to examine linear and quadratic trends from 2014 to 2018 and the differences between 2017 and 2018, controlling for sex, race/ethnicity, poverty ratio, and cigarette smoking status. bCurrent use classified for respondents who reported now using e-cigarettes every day or some days. cSignificant year × age interaction (P < .001). dDaily use classified for respondents who reported now using e-cigarettes every day. eSignificant quadratic trend for year in overall sample (P = .03). fSignificant quadratic trend for year in respective age group (P = .045). gNonsignificant linear (P = .49) and quadratic (P = .24) trends for year in respective age group. hSignificant linear trend for year in respective age group (P < .001). iSignificant year × age interaction (P = .009). jSignificant linear trend for year in overall sample (P = .02). kSignificant linear trend for year for respective age group (P = .007). lNonsignificant linear (P = .09) and quadratic (P = .31) trends for year in respective age group. mNonsignificant linear (P = .18) and quadratic (P = .43) trends for year in respective age group. nSignificant year × age interaction (P = .01).
Among young adults, 2014-2018 reported current e-cigarette use trends significantly increased among never and former smokers and every demographic subgroup except Hispanics (Table). E-cigarette use increases during 2017-2018 were significant among former smokers, men, non-Hispanic whites, persons of other race, and those with poverty ratio of 4.0 or greater.
Table. e-Cigarette Use Prevalence Among US Young Adults Aged 18-24 Years, 2014-2018, by Demographics and Smoking Status (N = 13 452).
| Characteristic | Current e-Cigarette Use Among Young Adults 18-24 y, Weighted % (95% CI)a,b | 2014-2018 | 2017-2018 | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 2014 (n = 3353) | 2015 (n = 2890) | 2016 (n = 3024) | 2017 (n = 2328) | 2018 (n = 1857) | P Value (Linear Trend)c | P Value (Quadratic Trend)c | Difference, 2018 vs 2017 (95% CI) | P Valuec | |
| Overall | 5.1 (3.5-6.7) | 5.2 (4.2-6.1) | 4.7 (3.5-5.9) | 5.2 (3.9-6.5) | 7.6 (6.1-9.1) | <.001 | .04 | 2.4 (0.4 to 4.4) | .008 |
| Cigarette smoking statusd | |||||||||
| Never | 1.5 (0.7-2.2) | 2.5 (1.7-3.3) | 2.1 (1.3-3.0) | 3.2 (1.8-4.6) | 4.6 (3.4-5.8) | <.001 | .63 | 1.4 (−0.5 to 3.2) | .17 |
| Former | 10.4 (3.6-17.3) | 19.6 (10.6-28.7) | 17.5 (9.4-25.6) | 15.8 (9.3-22.2) | 36.5 (24.0-49.0) | .004 | .34 | 20.8 (6.7 to 34.9) | .01 |
| Current | 20.0 (12.3-27.8) | 17.4 (13.1-21.6) | 16.1 (11.0-21.1) | 16.1 (11.0-21.1) | 22.1 (14.5-29.7) | .86 | .14 | 6.0 (−3.1 to 15.1) | .20 |
| Sex | |||||||||
| Men | 5.8 (4.4-7.2) | 7.8 (6.0-9.6) | 7.1 (4.9-9.3) | 6.4 (4.3-8.4) | 10.2 (7.8-12.6) | <.001 | .54 | 3.8 (0.7 to 7.0) | .02 |
| Women | 4.4 (1.5-7.3) | 2.5 (1.8-3.2) | 2.3 (1.4-3.1) | 4.0 (2.3-5.8) | 4.9 (3.3-6.6) | .03 | .01 | 0.9 (−1.5 to 3.4) | .27 |
| Race/ethnicitye | |||||||||
| Non-Hispanic white | 6.5 (3.8-9.3) | 6.2 (4.7-7.6) | 5.7 (4.2-7.1) | 5.9 (4.5-7.3) | 9.5 (7.3-11.7) | .003 | .06 | 3.5 (0.9 to 6.2) | .001 |
| Non-Hispanic black | 0.9 (0.0-1.8) | 1.6 (0.0-3.3) | 2.8 (0.2-5.4) | 4.3 (1.0-7.6) | 3.1 (0.4-5.8) | <.001 | .32 | −1.2 (−5.4 to 3.1) | .79 |
| Hispanic | 4.8 (2.3-7.3) | 4.9 (2.9-6.9) | 2.8 (0.6-5.0) | 4.8 (1.1-8.6) | 5.2 (2.2-8.1) | .48 | .23 | 0.3 (−4.5 to 5.1) | .80 |
| Other | 3.4 (1.3-5.5) | 5.3 (2.2-8.4) | 6.5 (2.5-10.5) | 3.0 (1.1-5.0) | 8.5 (3.9-13.0) | .02 | .44 | 5.5 (0.5 to 10.4) | .02 |
| Poverty ratiof | |||||||||
| <1.0 | 4.5 (2.6-6.5) | 3.2 (2.0-4.5) | 4.0 (2.0-6.0) | 4.9 (3.1-6.8) | 7.5 (4.5-10.4) | .003 | .14 | 2.5 (−1.0 to 6.0) | .18 |
| 1.0-3.9 | 5.3 (3.8-6.9) | 6.2 (4.6-7.7) | 5.7 (4.0-7.4) | 6.2 (3.7-8.6) | 8.5 (6.3-10.7) | .001 | .36 | 2.3 (−1.0 to 5.6) | .10 |
| ≥4.0 | 1.9 (0.7-3.1) | 5.8 (3.2-8.5) | 3.8 (1.8-5.7) | 3.2 (1.5-4.9) | 7.5 (4.2-10.7) | .005 | .43 | 4.3 (0.6 to 8.0) | .008 |
Current e-cigarette use classified for respondents who reported now using e-cigarettes every day or some days.
Weighted estimates take into account the complex survey design using Taylor series variance estimation.
Logistic regression was used to examine linear and quadratic trends from 2014 to 2018 and the differences between 2017 and 2018, controlling for sex, race/ethnicity, poverty ratio, and cigarette smoking status.
Combustible cigarette smoking status was classified into never (<100 cigarettes smoked lifetime), former (smoked ≥100 cigarettes lifetime and not currently smoking), or current (smoked ≥100 cigarette lifetime and currently smoking every day or some days).
Race and Hispanic ethnicity were self-reported; Hispanic persons could be of any race.
Ratio of family income to federal poverty threshold.
Discussion
Over 2014-2018, prevalence of reported current and daily e-cigarette use increased among US young adults but declined or remained stable in older age groups. The 46.2% increase (5.2% to 7.6%) in current e-cigarette use from 2017-2018 among young adults paralleled concurrent 48.5% and 77.8% increases in US middle and high school students, respectively,1 although cross-survey methodological differences preclude direct comparisons of adolescent and young adult estimates.
Sales of pod-mod–style e-cigarette products with high nicotine concentrations and appealing flavors increased during 2017-2018.6 Increasing e-cigarette use by young adults may be explained by increasing use of pod-mod products by young adults.
E-cigarette use increased in most young adult demographic and smoking subgroups, including never smokers, from 2014-2018. Why 2017-2018 biannual increases were observed only among subpopulations, such as men and former smokers, merits further research.
Study limitations are that self-report information is subject to recall errors. Extending ongoing public health campaigns regarding e-cigarette use by young adults warrants consideration.
Section Editor: Jody W. Zylke, MD, Deputy Editor.
References
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