Changes in Electronic Cigarette Use Among Adults in the United States, 2014-2016

Abstract

This study analyzes National Health Interview Survey data to characterize changes in electronic cigarette use among US adults in 2014-2016.

Electronic cigarettes (e-cigarettes) are widely marketed as a tool for smoking cessation and a safer alternative to conventional cigarettes. However, the efficacy of e-cigarettes for successful smoking cessation is inconclusive.^1,2 Previous studies have reported a rapid increase in the prevalence of e-cigarette use among US adults since 2010.^3,4,5 We analyzed new national survey data to estimate the changes in e-cigarette use among US adults in 2014-2016.

Methods

The National Health Interview Survey (NHIS) is a nationally representative annual health survey of the noninstitutionalized, civilian US population. NHIS collects information about health-related topics through in-person household interviews.⁴ In NHIS 2014-2016, the household response rate ranged from 67.9% to 73.8%. The University of Iowa institutional review board determined that the current study was exempt given the use of deidentified data.

Since 2014, participants 18 years or older were asked about their lifetime use of e-cigarettes:⁴ “Have you ever used an e-cigarette, even 1 time?” Adults who had ever used an e-cigarette were then asked, “Do you now use e-cigarettes every day, some days, or not at all?” Current use of e-cigarettes was defined as using e-cigarettes every day or some days.⁴ Participants were also asked about their ever and current use of conventional cigarettes (not including e-cigarettes).

We estimated the prevalence of ever and current e-cigarette use in 2014, 2015, and 2016 overall and by age, sex, race/ethnicity, income, and cigarette smoking, with survey weights to account for unequal probability of selection and nonresponse. P values for differences between years and across population strata were calculated using the F test. Trends in prevalence over the 3 years were tested using a weighted logistic regression model with survey year as a continuous variable. All data analyses were conducted using survey procedures in SAS (SAS Institute), version 9.4. A 2-sided P value less than .05 was considered statistically significant.

Results

This analysis included 101 175 NHIS participants 18 years or older (women, 55.1%; non-Hispanic white, 64.7% ; non-Hispanic black, 12.4% ; Hispanic, 14.7%). The weighted prevalence of ever use of e-cigarettes increased significantly from 2014 to 2016 (12.6% [95% CI, 12.0%-13.2%] in 2014, 13.9% [95% CI, 13.3%-14.5%] in 2015, and 15.3% [95% CI, 14.6%-15.9%] in 2016; P for trend, <.001). Almost all the subgroups evaluated showed a significant increase (Table).

Table. Prevalence of Ever Use and Current Use of e-Cigarettes Among US Adults, 2014-2016 (N = 101 175).

Characteristic	Prevalence, % (95% CI)a			Changes Across Years, % (95% CI)a			P Value for Trendb
	2014	2015	2016	2014 vs 2015	2015 vs 2016	2014 vs 2016
Ever Use of e-Cigarettes
e-Cigarette users/participants, No.	4451/36 520	4316/31 724	4900/32 931
Overall	12.6 (12.0 to 13.2)	13.9 (13.3 to 14.5)	15.3 (14.6 to 15.9)	1.3 (0.5 to 2.1)	1.3 (0.5 to 2.2)	2.6 (1.8 to 3.5)	<.001
Age, y
18-44	18.0 (17.0 to 19.0)	20.0 (18.9 to 21.1)	21.8 (20.7 to 22.9)	2.0 (0.6 to 3.5)	1.8 (0.3 to 3.3)	3.8 (2.3 to 5.3)	<.001
45-64	10.2 (9.3 to 11.1)	11.3 (10.5 to 12.1)	12.6 (11.8 to 13.5)	1.1 (−0.1 to 2.3)	1.4 (0.2 to 2.6)	2.5 (1.2 to 3.7)	<.001
≥65	3.7 (3.2 to 4.2)	4.0 (3.4 to 4.6)	4.4 (3.8 to 5.0)	0.3 (−0.5 to 1.1)	0.4 (−0.4 to 1.2)	0.7 (−0.04 to 1.5)	.06
Sex
Men	14.2 (13.3 to 15.1)	16.2 (15.3 to 17.1)	17.7 (16.8 to 18.7)	2.0 (0.7 to 3.3)	1.6 (0.3 to 2.9)	3.5 (2.2 to 4.9)	<.001
Women	11.1 (10.4 to 11.9)	11.8 (11.1 to 12.5)	13.0 (12.2 to 13.7)	0.7 (−0.3 to 1.7)	1.1 (0.1 to 2.2)	1.8 (0.8 to 2.9)	<.001
Race/ethnicityc
Hispanic	8.4 (7.3 to 9.5)	10.0 (8.9 to 11.1)	11.1 (9.6 to 12.6)	1.6 (0.1 to 3.0)	1.1 (−0.7 to 2.9)	2.7 (0.8 to 4.5)	.004
Non-Hispanic white	14.8 (14.0 to 15.6)	15.8 (15.0 to 16.6)	17.2 (16.5 to 18.0)	1.1 (−0.1 to 2.2)	1.4 (0.3 to 2.5)	2.5 (1.3 to 3.6)	<.001
Non-Hispanic black	7.1 (6.2 to 8.0)	9.7 (8.5 to 10.9)	11.5 (9.7 to 13.4)	2.6 (1.1 to 4.0)	1.9 (−0.3 to 4.0)	4.4 (2.4 to 6.4)	<.001
Non-Hispanic other	10.7 (9.0 to 12.3)	12.0 (10.3 to 13.6)	13.1 (11.2 to 15.0)	1.3 (−0.8 to 3.4)	1.1 (−1.4 to 3.7)	2.4 (−0.1 to 5.0)	.07
Family income:poverty ratio
<1.0	16.0 (14.5 to 17.4)	19.6 (17.8 to 21.4)	20.1 (18.1 to 22.0)	3.6 (1.3 to 6.0)	0.5 (−2.2 to 3.1)	4.1 (1.7 to 6.5)	<.001
1.0-1.9	15.3 (14.0 to 16.5)	16.3 (14.9 to 17.7)	19.1 (17.2 to 21.0)	1.1 (−0.8 to 2.9)	2.8 (0.5 to 5.2)	3.9 (1.6 to 6.2)	<.001
2.0-3.9	15.0 (13.9 to 16.2)	16.2 (15.1 to 17.3)	18.2 (16.9 to 19.5)	1.2 (−0.4 to 2.7)	2.0 (0.2 to 3.7)	3.1 (1.3 to 4.9)	<.001
≥4.0	10.0 (8.9 to 11.2)	11.3 (10.4 to 12.3)	12.4 (11.4 to 13.3)	1.3 (−0.2 to 2.8)	1.0 (−0.3 to 2.3)	2.3 (0.8 to 3.8)	.004
Conventional cigarette used
Current smoker	47.6 (45.5 to 49.6)	53.2 (51.2 to 55.3)	52.5 (50.6 to 54.4)	5.7 (2.8 to 8.6)	−0.7 (−3.5 to 2.0)	5.0 (2.1 to 7.8)	<.001
Former smoker	12.3 (11.2 to 13.3)	14.8 (13.7 to 16.0)	16.2 (15.0 to 17.3)	2.5 (1.0 to 4.0)	1.4 (−0.3 to 3.0)	3.9 (2.3 to 5.5)	<.001
Never smoker	3.2 (2.8 to 3.6)	4.3 (3.8 to 4.7)	5.7 (5.2 to 6.2)	1.1 (0.4 to 1.7)	1.4 (0.7 to 2.1)	2.5 (1.9 to 3.1)	<.001
Current Use of e-Cigarettes
e-Cigarette users/participants, No.	1276/36 520	1029/31 724	983/32 931
Overall	3.7 (3.3 to 4.1)	3.5 (3.2 to 3.7)	3.2 (2.9 to 3.5)	−0.3 (−0.8 to 0.2)	−0.3 (−0.7 to 0.1)	−0.6 (−1.1 to −0.1)	.02
Age, y
18-44	4.8 (4.2 to 5.4)	4.6 (4.1 to 5.0)	4.4 (3.8 to 4.9)	−0.3 (−1.0 to 0.5)	−0.2 (−0.9 to 0.5)	−0.5 (−1.3 to 0.3)	.26
45-64	3.5 (2.9 to 4.1)	3.3 (2.8 to 3.7)	2.8 (2.4 to 3.2)	−0.3 (−1.0 to 0.5)	−0.4 (−1.0 to 0.2)	−0.7 (−1.4 to 0.0)	.06
≥65	1.4 (1.1 to 1.8)	1.1 (0.8 to 1.4)	1.0 (0.7 to 1.2)	−0.3 (−0.8 to 0.2)	−0.2 (−0.6 to 0.2)	−0.5 (−0.9 to −0.0)	.03
Sex
Men	4.1 (3.5 to 4.8)	4.3 (3.9 to 4.8)	3.8 (3.4 to 4.3)	0.2 (−0.6 to 1.0)	−0.5 (−1.1 to 0.2)	−0.3 (−1.1 to 0.5)	.44
Women	3.4 (2.9 to 3.9)	2.6 (2.3 to 3.0)	2.6 (2.2 to 2.9)	−0.7 (−1.3 to −0.1)	−0.1 (−0.5 to 0.4)	−0.8 (−1.4 to −0.2)	.007
Race/ethnicityc
Hispanic	2.0 (1.5 to 2.5)	1.8 (1.3 to 2.3)	1.6 (1.0 to 2.1)	−0.2 (−0.8 to 0.5)	−0.3 (−1.0 to 0.5)	−0.4 (−1.2 to 0.3)	.27
Non-Hispanic white	4.6 (4.0 to 5.2)	4.1 (3.7 to 4.5)	3.7 (3.3 to 4.1)	−0.5 (−1.2 to 0.3)	−0.4 (−1.0 to 0.1)	−0.9 (−1.6 to −0.2)	.01
Non-Hispanic black	1.8 (1.4 to 2.3)	1.9 (1.4 to 2.4)	2.0 (1.2 to 2.8)	0.0 (−0.7 to 0.8)	0.2 (−0.8 to 1.1)	0.2 (−0.7 to 1.1)	.66
Non-Hispanic other	2.9 (2.0 to 3.9)	3.4 (2.3 to 4.6)	3.7 (2.5 to 4.9)	0.5 (−0.9 to 1.9)	0.2 (−1.4 to 1.8)	0.7 (−0.8 to 2.3)	.36
Family income:poverty ratio
<1.0	4.9 (4.2 to 5.7)	5.2 (4.1 to 6.2)	3.5 (2.6 to 4.3)	0.2 (−1.1 to 1.6)	−1.7 (−3.0 to −0.4)	−1.5 (−2.6 to −0.3)	.01
1.0-1.9	4.5 (3.8 to 5.2)	4.4 (3.7 to 5.2)	4.7 (3.7 to 5.6)	−0.0 (−1.0 to 0.9)	0.2 (−1.0 to 1.5)	0.2 (−1.0 to 1.4)	.74
2.0-3.9	4.4 (3.7 to 5.0)	3.7 (3.1 to 4.3)	3.9 (3.3 to 4.6)	−0.7 (−1.6 to 0.2)	0.2 (−0.7 to 1.1)	−0.5 (−1.4 to 0.5)	.33
≥4.0	2.8 (1.9 to 3.7)	2.8 (2.4 to 3.3)	2.3 (2.0 to 2.7)	−0.0 (−1.0 to 1.0)	−0.5 (−1.1 to 0.1)	−0.5 (−1.5 to 0.5)	.29
Conventional cigarette used
Current smoker	15.9 (14.2 to 17.6)	13.6 (12.2 to 14.9)	10.8 (9.6 to 12.0)	−2.3 (−4.5 to −0.2)	−2.8 (−4.6 to −1.0)	−5.1 (−7.2 to −3.0)	<.001
Former smoker	3.8 (3.1 to 4.5)	4.7 (4.0 to 5.4)	4.8 (4.2 to 5.5)	0.9 (−0.1 to 1.9)	0.1 (−0.8 to 1.1)	1.0 (0.1 to 2.0)	.03
Never smoker	0.4 (0.3 to 0.5)	0.6 (0.5 to 0.8)	0.7 (0.5 to 0.9)	0.2 (0.0 to 0.4)	0.1 (−0.2 to 0.3)	0.3 (0.0 to 0.5)	.02

^aAll estimates, except the numbers of participants and e-cigarette users, were weighted.

^bP values for trends in prevalence from 2014 to 2016.

^cRace and Hispanic ethnicity were self-reported and classified based on the 1997 Office of Management and Budget standards.

^dConventional cigarette smoking did not include e-cigarettes. Adults who had not smoked 100 cigarettes in their lifetime were classified as never smokers. Adults who had ever smoked 100 cigarettes were classified as (1) current smokers if they currently smoked every day or some days; or (2) former smokers if they were not currently smoking.⁴

In contrast, the weighted prevalence of current use of e-cigarettes decreased significantly from 2014 to 2016 (3.7% [95% CI, 3.3%-4.1%] in 2014, 3.5% [95% CI, 3.2%-3.7%] in 2015, and 3.2% [95% CI, 2.9%-3.5%] in 2016; P for trend, .02). The decrease was significant in subgroups including individuals 65 years or older, women, non-Hispanic white participants, low-income participants, and current cigarette smokers. However, the prevalence increased significantly among former smokers and never smokers (Table).

Discussion

In a nationally representative survey among US adults, there was a significant increase in the prevalence of ever use of e-cigarettes between 2014 and 2016. In contrast, the prevalence of current e-cigarette use among US adults declined significantly between 2014 and 2016. These trends may suggest that some individuals are trying but not continuing use of e-cigarettes, but further investigation with individual longitudinal data on use of both e-cigarettes and other nicotine products is needed. Coincident with these findings among adults, the National Youth Tobacco Survey reported that the prevalence of current e-cigarette use among US middle and high school students declined for the first time in 2016, after a continuous increase from 2011 to 2015.⁶

In this study, current use of e-cigarettes declined among current smokers but increased among former smokers. This pattern may reflect e-cigarette use as adults are transitioning from current to former smokers, but further investigation is warranted. The observed increase in both ever and current e-cigarette use among never smokers is concerning, because these never smokers were being exposed to nicotine and other harmful ingredients.

The main limitation of the study is the relatively short period of observation. Continued surveillance and weighing the long-term risks and benefits of e-cigarette use on public health are warranted.

Section Editor: Jody W. Zylke, MD, Deputy Editor.