Nicotine & Tobacco Research Advance Access published November 29, 2014 Nicotine & Tobacco Research, 2014, 1–8 doi:10.1093/ntr/ntu213 Original investigation
Original investigation
Trends in Electronic Cigarette Use Among U.S. Adults: Use is Increasing in Both Smokers and Nonsmokers Downloaded from http://ntr.oxfordjournals.org/ at University of Manitoba on June 9, 2015
Robert C. McMillen PhD1, Mark A. Gottlieb JD2, Regina M. Whitmore Shaefer MPH3, Jonathan P. Winickoff MD, MPH4, Jonathan D. Klein, MD, MPH3 Department of Psychology, Mississippi State University and American Academy of Pediatrics Julius B. Richmond Center of Excellence, Starkville, MS; 2Public Health Advocacy Institute at Northeastern University School of Law and American Academy of Pediatrics Julius B. Richmond Center of Excellence, Boston, MA; 3American Academy of Pediatrics Julius B. Richmond Center of Excellence, Elk Grove Village, IL; 4Department of General Pediatrics, MGH Center for Child and Adolescent Health Policy and American Academy of Pediatrics Julius B. Richmond Center of Excellence, Boston, MA 1
Corresponding Author: Robert C. McMillen, PhD, Mississippi State University and American Academy of Pediatrics, Julius B. Richmond Center of Excellence, One Research Park, Suite 103, Starkville, MS 39759, USA. Telephone: 662-325-7127; Fax: 663-325-7966; E-mail: [email protected]
Abstract Objectives: We assessed trends in use of electronic cigarettes among U.S. adults, demographic predictors of use, and smoking status of current electronic cigarette users. Methods: Mixed-mode surveys were used to obtain representative, cross-sectional samples of U.S. adults in each of 4 years. Results: Sample sizes for 2010, 2011, 2012, and 2013 were 3,240, 3,097, 3,101, and 3,245, respectively. Ever use of electronic cigarettes increased from 1.8% (2010) to 13.0% (2013), while current use increased from 0.3% to 6.8%, p < .001. Prevalence of use increased significantly across all demographic groups. In 2013, current use among young adults 18–24 (14.2%) was higher than adults 25–44 (8.6%), 45–64 (5.5%), and 65+ (1.2%). Daily smokers (30.3%) and nondaily smokers (34.1%) were the most likely to currently use e-cigarettes, compared to former smokers (5.4%) and never-smokers (1.4%), p < .001. However, 32.5% of current electronic cigarette users are never- or former smokers. Conclusions: There has been rapid growth in ever and current electronic cigarette use over the past 4 years. Use is highest among young adults and current cigarette smokers. Although smokers are most likely to use these products, almost a third of current users are nonsmokers, suggesting that e-cigarettes contribute to primary nicotine addiction and to renormalization of tobacco use. Regulatory action is needed at the federal, state, and local levels to ensure that these products do not contribute to preventable chronic disease.
Introduction Electronic cigarettes entered the U.S. market in 2007, and the affordability, availability, and marketing of these products has increased over the recent years.1 The U.S. Food and Drug Administration (FDA) attempted and failed to regulate these products as drug delivery devices, and thus subject them to the stringent “safe and effective”
standard required for drug approvals.2 The judge stated the FDA has the authority to regulate electronic cigarettes as tobacco products if they choose to do so, but could not regulate them as drugs or drug/ delivery device combination products unless the companies make therapeutic claims or demonstrate they intend their product for a therapeutic purpose. The FDA announced its intention to do so in
© The Author 2014. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: [email protected].
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differences in quitting among the randomized groups at six months. Other studies used longitudinal population designs to examine the relationship between e-cigarette use and quitting over one year. Two of these studies found no statistically significant differences in the odds of quitting tobacco cigarettes at one-year follow-up between smokers who had used e-cigarettes at baseline and smokers who had not,4,15,16 whereas the third study found a statistically significantly lower likelihood of quitting among e-cigarette triers compared to non-triers.14 In the absence of sufficient data and FDA regulation, the public health community needs more research on the population prevalence of electronic cigarette use and the characteristics of people who use these products. A recent overview summarizes many of the concerns regarding electronic cigarettes. Broadly, these concerns involve the unknown characteristics of this product, the health effects for users and nonusers exposed to the vapor, the impact of use on cigarette smoking behaviors, the lack of evidence that these products increase efficacy in cigarette smoking cessation, and the lack of any product regulation.17 Specifically, many electronic cigarettes have unknown levels of nicotine, unknown ingredients, technical flaws, and variable quality.2,18–24 Moreover, the known ingredients of electronic cigarettes have not been demonstrated to be safe for humans, when heated to temperatures sufficient to create a vapor. Citing these issues as well as concerns about the rapid growth in market, growth in internet presence and advertising,25–27 and appeal to youth, several scientists and organizations, including the National Association of Attorneys General, have urged the FDA assert their authority over tobacco products to include electronic cigarettes.2,23,28–32 To date, the limited amount of research on the social penetration of electronic cigarettes indicates annual growth in both awareness and use of electronic cigarettes. A recent Centers for Disease Control and Prevention study found an increase in ever use of electronic cigarettes among both U.S. middle and high school students from 2011 to 2012.33 Among U.S. adults, ever use of these products in 2010 ranged from 1.8% to 3.4%,3,34–36 and had increased from 2009.36 Use of these products continued to increase in 2011, with 5.8% of U.S. adults reporting ever use of electronic cigarettes.3 Collectively, these studies illustrate continuous growth in use of these products from 2009 to 2011. Recent financial analyses suggest continued growth in market.37 Not surprisingly use of electronic cigarettes is more common among cigarette smokers and users of other tobacco products than among non-tobacco users.3,34–36 Ever use of these products has also been found to vary by educations status,34,36 income36, and sex36. In summary, the use of electronic cigarettes is expected to be increasing and there is a variability in use prevalence across subpopulations. Although use is substantially higher among smokers than nonsmokers, several studies have found nontrivial levels of use among nonsmokers. The purpose of this study is to assess trends in use of electronic cigarettes among U.S. adults, demographic predictors of use, and smoking status of current electronic cigarette users. Results from this study can inform regulatory decisions about these products, while the identification of potential high risk demographic groups can guide clinical counseling efforts regarding the risks of any tobacco or nicotine use.
Methods Cross-sectional dual-frame surveys representing national probability samples of adults were administered in 2010, 2011, 2012, and 2013. The design included a Random Digit Dialing (RDD) frame and an internet panel frame developed from a probability sample of U.S. adults, in
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April 2011 under its authority provided by the Tobacco Control Act,3 and released a draft of the deeming rule in April 2014. According to proposed deeming rule, makers of newly deemed tobacco products would be required to (a) register with FDA and report product and ingredient listings (but it is not clear if this applies to the FDA or to the consumer), (b) only market new products after FDA review, (c) not distribute free samples, (d) include a health warning label, and (e) restrict sale of electronic cigarettes to adults 18 years of age and older. The draft does not eliminate online sales, eliminate flavors, address child safety issues, or regulate or limit marketing. The comment period for this deeming rule expires in August 2014 and the FDA anticipates a final action in June 2015. The proposed regulatory oversight on electronic cigarettes is lighter in the United States than for much of the global community. These products are not currently legal in Brazil and Singapore; and Canada and Australia restrict the sale of nicotine containing electronic cigarettes to products that have been submitted to and approved by their medicine regulatory agencies.4,5 In Europe, the restrictions and regulations also differ from the United States. The European Union approved new rules in February 2014 that will ban electronic cigarette advertising, the products will have to be childproof, packages will have to have safety warnings, and the dosage will be limited to 20 mg of nicotine. These regulations are scheduled to be implemented in 2016.6 Currently, there are several gaps in regulation of electronic cigarettes. Neither the FDA nor the Consumer Product Safety Commission oversees the safety and manufacturing of these products. Marketing of electronic cigarettes is regulated by general advertising rules, but not the additional regulations that apply to cigarettes and smokeless tobacco. Although federal law has prohibited tobacco advertisements on television and radio since 1972, these venues are now home to advertisements for electronic cigarettes.7 These products do not meet many states’ definition of tobacco products, and thus tobacco taxation rates and age of purchase requirements do not apply in these states. Although three states and 188 communities include the restriction of electronic cigarettes use in their comprehensive smokefree policies,8 many state and local smokefree laws predate the development of electronic cigarettes. Thus the use of electronic cigarettes is still permissible in many places in which combustible tobacco products are prohibited. The unknown risks of electronic cigarettes are likely to be less harmful than combustible cigarettes. Although research on the harms of secondhand vapor is limited, electronic cigarettes can produce volatile organic compounds, heavy metals, and other toxins in the vapor released, albeit in lower levels than combustible tobacco.9–12 Harm reduction proponents highlight this decreased risk, and view electronic cigarettes as means to reduce exposure to combustible tobacco, and perhaps even as a cessation tool for smokers.13 There are, however, some important possibilities to consider. Specifically, electronic cigarettes could contribute to primary nicotine addiction among youth and young adults and to renormalization of smoking behaviors. Moreover, use of electronic cigarettes by smokers who are motivated to quit and are strong candidates for evidence-based smoking cessation treatment may complicate treatment because electronic cigarettes are not approved nor incorporated into clinical practice guidelines. Although many cigarette smokers who have tried electronic cigarettes report doing so as a strategy for quitting smoking,4,14 the limited number of studies examining use of electronic cigarettes and cessation have not supported this strategy. Bullen13 tested the effectiveness of e-cigarettes for cessation by randomly assigning smokers to use e-cigarettes or the nicotine patch; and found no statistically significant
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Self-Reported Use of Electronic Cigarettes Respondents were asked “Have you ever heard of a product called electronic cigarettes or e-cigarettes, or brands such as Smoking Everywhere, NJOY, Blu, or others?” Respondents who had heard of electronic cigarettes were asked, “Have you tried Electronic Cigarettes or E-cigarettes, even just one time?” Respondents who reported yes were classified as having tried electronic cigarettes. Those who had tried electronic cigarettes were asked, “Do you now use e-cigarettes every day, some days, or not at all.” Respondents who reported every day or some days were classified as current users.
Self-Reported Smoking Respondents were asked, “Have you smoked at least 100 cigarettes in your entire life?” Respondents who reported that they had were then asked, “Do you now smoke cigarettes every day, some days, or not at all?” Respondents who reported that they have smoked at least 100 cigarettes and now smoke every day or some days were categorized as current smokers, while those who reported not at all were categorized as former smokers. Former smokers were asked, “About how long has it been since you last smoked cigarettes regularly?” In analyses of electronic cigarette use among never- and former smokers, former smokers who had quit smoking less than five years ago were considered to be recent former smokers and those who had quit more than five years ago (and before electronic cigarettes entered the U.S. market) were considered to distant former smokers.
Analyses Data for overall and subpopulation ever and current use of electronic cigarettes were examined to assess three year trends from 2010 to 2013. Using 2013 data, we examined demographic factors associated with electronic cigarette with multivariable logistic regression and examined nonsmokers’ contribution to the electronic
cigarette market. Finally, bivariate analyses were applied compared current electronic use among never-smokers, former smokers, and current smokers.
Results Sample Characteristics Table 1 shows the demographic characteristics of the overall sample. 2010 In the RDD frame, of 2,128 eligible respondents contacted, 1,504 (70.7%) completed surveys. For the internet panel frame, 2,272 panelists were randomly drawn from the probability panel; 1,736 responded to the invitation, yielding a final stage completion rate of 67.5%.42 Length of time on the panel for the internet panel frame ranged from 0.09 to 11.08 years, with a median length of time on the panel of 2.29 years. The total sample size was 3,240. 2011 In the RDD frame, of 2,282 eligible respondents contacted, 1,500 (63%) completed surveys. For the probability-based panel frame, 2,476 panelists were randomly drawn from the probability panel; 1,597 responded to the invitation, yielding a final stage completion rate of 65%. Length of time on the panel for the probability-based panel frame ranged from 0.18 to 11.93 years, with a median length of time on the panel of 1.4 years. The total sample size was 3,097. 2012 In the RDD frame, of 1,713 eligible respondents contacted, 1,507 (88.0%) completed surveys. For the probability-based panel frame, 2,529 panelists were randomly drawn from the probability panel; 1,594 responded to the invitation, yielding a final stage completion rate of 63%. Length of time on the panel for the probability-based panel frame ranged from 0.06 to 12.89 years, with a median length of time on the panel of 1.48 years. The total sample size was 3,101. 2013 In the RDD frame, of 1,689 eligible respondents contacted, 1,552 (91.9%) completed surveys. For the probability-based panel frame, 2,667 panelists were randomly drawn from the probability panel; 1,693 responded to the invitation, yielding a final stage completion rate of 63.5%. Length of time on the panel for the probability-based panel frame ranged from 0.12 to 13.97 years, with a median length of time on the panel of 2.16 years. The total sample size was 3,245.
Trends In weighted analysis, ever use of electronic cigarettes increased from 1.8% to 13.0% (Table 2). Among subpopulations, ever use also increased significantly across all assessed groups over the four year period (p < .05 for all comparisons). Although nondaily smokers and daily smokers had the highest absolute increases in ever use of electronic cigarettes, use among never- and former smokers also increased. Current use also demonstrated substantial growth; prevalence increased from 0.3% in 2010 to 6.8% in 2013. Table 3 summarizes subpopulation trends. Overall, ever use of electronic cigarettes increased by 622% (Table 2) and current use increased by 2,167% (Table 3) from 2010 to 2013. Increases in use were substantial across all demographic groups. We did not reweight the data from the four cross-sectional
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order to reduce non-coverage issues arising from wireless substitution. Wireless substitution of cell phones for landlines continues to increase, and 39.4% of U.S. households are currently wireless only.38 The RDD frame included households with listed and unlisted landline telephones; five attempts were made to contact those selected adults who were not home. The Survey Research Laboratory at Mississippi State University’s Social Science Research Center administered the surveys via computer-assisted telephone interviews to respondents in this frame. The probability-based panel frame included an online survey conducted by Knowledge Networks, administered to a randomly selected sample from a nationally representative research panel.39,40 This panel is based on a sampling frame which includes both listed and unlisted numbers, those without a landline telephone, and does not accept self-selected volunteers,39,40 and provides sample coverage for 99% of U.S. households.41 Surveys were administered to both frames from October to November in 2010, 2011, 2012, and 2013. The Institutional Review Board (IRB) at Mississippi State University approved this study. For the RDD frame, informed verbal consent was obtained and the IRB provided a waiver of documentation of the written consent process. For the probability-based panel frame, participants were presented with an informed consent statement, and clicked continue if they agreed to participate. More detailed methods have been previously published.34 Within each year, data were weighted to adjust for age, race, sex, and region, as well as frame overlap among internet panel respondents who also had a landline telephone and were therefore also eligible for the RDD frame.
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4 Table 1. Weighted Sample Characteristics 2011 (unweighted n = 3,097)
2012 (unweighted n = 3,101)
2013 (unweighted n = 3,245)
56.9% 24.8% 4.6% 13.7%
56.9% 25.0% 3.4% 14.7%
59.6% 24.8% 3.8% 11.8%
59.9% 24.6% 4.3% 10.1%
12.6% 18.4% 37.6% 31.4%
12.9% 18.9% 37.2% 31.0%
17.8% 21.7% 37.5% 23.0%
17.3% 22.1% 37.8% 22.2%
74.2% 11.5% 14.3%
69.5% 11.3% 19.2%
71.5% 11.4% 17.1%
70.3% 11.3% 17.5%
13.7% 38.8% 33.3% 14.2%
9.3% 39.7% 34.9% 16.1%
11.4% 38.3% 34.7% 15.6%
10.7% 37.3% 34.3% 16.2%
47.6% 52.4%
48.3% 51.7%
48.1% 51.9%
47.4% 52.6%
9.2% 28.5% 29.3% 33.0%
10.5% 27.3% 29.6% 32.6%
9.9% 28.8% 28.1% 33.4%
9.0% 26.9% 28.9% 34.9%
Table 2. Prevalence of Electronic Cigarette Ever Use 2010, % (95% CI) 2011, % (95% CI) 2012, % (95% CI) 2013, % (95% CI) Relative percent change, (unweighted n = 3,240) (unweighted n = 3,097) (unweighted n = 3,101) (unweighted n = 3,245) 2010–2013 Overall Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High school Some college College degree
1.8 (1.3–2.3)
7.3 (6.4–8.2)
10.6 (9.5–11.7)
13.0 (11.8–14.2)
622%
0.3 (0.0–0.6 1.5 (0.7–2.3) 8.2 (2.6–13.8) 6.2 (4.0–8.4)
1.2 (0.7–1.7) 6.5 (4.8–8.2) 13.9 (6.5–21.3) 30.9 (26.4–35.4)
2.4 (1.7–3.1) 11.7 (9.5–13.9) 27.1 (18.3–35.9) 44.6 (39.3–49.9)
3.5 (2.7–4.3) 13.5 (11.1–15.9) 47.0 (38.5–55.5) 54.2 (48.7–59.7)
1,067% 800% 473% 774%
2.7 (1.4–4.0) 1.4 (0.6–2.2) 1.6 (0.9–2.3) 1.9 (0.8–3.0)
4.8 (3.0–6.6) 7.8 (5.9–9.7) 7.0 (5.5–8.5) 8.2 (6.1–10.3)
8.9 (6.5–11.3) 12.9 (10.5–15.3) 10.0 (8.3–11.7) 10.6 (8.2–13.0)
10.1 (7.5–12.7) 11.6 (9.2–14.0) 14.9 (12.9–16.9) 14.1 (11.5–16.7)
274% 729% 831% 642%
1.7 (1.2–2.2) 1.9 (0.3–3.5) 1.8 (0.4–3.2)
8.3 (7.2–9.4) 3.7 (1.7–5.7) 5.6 (3.4–7.8)
12.3 (11.0–13.6) 5.3 (2.8–7.8) 7.3 (4.7–9.9)
13.1 (11.7–14.5) 11.5 (8.1–14.9) 14.0 (11.1–16.9)
385% 721% 775%
2.5 (0.6–4.4) 2.1 (1.2–3.0) 1.6 (0.9–2.3) 0.4 (0.0–0.9)
7.3 (4.5–10.1) 10.7 (8.4–13.0) 4.9 (3.6–6.2) 4.4 (3.1–5.7)
15.0 (9.9–20.1) 13.9 (11.6–16.2) 9.6 (7.9–11.3) 2.3 (1.3–3.3)
21.0 (16.6–25.4) 15.7 (13.6–17.8) 12.2 (10.2–14.2) 4.8 (2.9–6.7)
1,005% 824% 542% 167%
2.2 (1.4–3.0) 1.4 (0.9–1.9)
8.8 (7.3–10.3) 5.8 (4.7–6.9)
11.1 (9.4–12.8) 10.1 (8.7–11.5)
13.9 (12.1–15.7) 12.4 (10.8–14.0)
456% 490%
0.7 (0.0–1.7) 1.7 (0.9–2.5) 3.7 (2.4–5.0) 0.5 (0.1–0.9)
11.6 (7.8–15.4) 7.5 (5.8–9.2) 8.3 (6.5–10.1) 4.8 (3.5–6.1)
8.5 (5.2–11.8) 14.0 (11.7–16.3) 13.9 (11.6–16.2) 5.6 (4.3–6.9)
16.9 (12.4–21.4) 14.9 (12.5–17.3) 18.9 (16.3–21.5) 6.2 (4.8–7.6)
956% 3,625% 759% 343%
Note. CI = confidence interval.
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Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High school Some college College degree
2010 (unweighted n = 3,240)
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Table 3. Prevalence of Electronic Cigarette Current Use 2011, % (95% CI) 2012, % (95% CI) 2013, % (95% CI) (unweighted n = 3,097) (unweighted n = 3,101) (unweighted n = 3,245)
Relative percent change, 2010–2013
0.3% (0.1–0.5)
0.8% (0.5–1.1)
2.6% (2.0–3.2)
6.8% (5.9–7.7)
2,167%
0.1% (0.0–0.2) 0.3% (0.0–0.7) 1.4% (0.0–3.3) 1.4% (0.3–2.5)
0.1% (0.0–0.2) 0.1% (0.0–0.3) 1.0% (0.0–2.9) 5.0% (3.0–7.0)
0.1% (0.0–0.2) 1.1% (0.4–1.8) 3.1% (0.0–6.5) 10.8% (7.5–14.1)
1.4% (0.9–1.9) 5.4% (3.8–7.0) 34.1% (26.0–42.2) 30.3% (25.2–35.4)
1,300% 1,700% 2,336% 2,064%
0.5% (0.0–1.2) 0.3% (0.0–0.7) 0.2% (0.0–0.5) 0.3% (0.0–0.6)
0.3% (0.0–0.8) 0.5% (0.0–1.1) 0.4% (0.0–0.8) 1.7% (0.9–2.5)
1.5% (0.5–2.5) 2.3% (1.2–3.4) 1.4% (0.7–2.1) 2.0% (0.9–3.1)
5.5% (3.6–7.4) 6.3% (4.5–8.1) 8.3% (6.7–9.9) 6.0% (4.2–7.8)
1,000% 2,000% 4,050% 1,900%
0.3% (0.1–0.5) 0.3% (0.0–0.9) 0.4% (0.0–1.0)
0.8% (0.4–1.2) 0.6% (0.0–1.4) 1.0% (0.2–1.8)
1.9% (1.4–2.4) 0.3% (0.0–0.9) 2.1% (0.7–3.5)
6.7% (5.6–7.8) 4.3% (2.2–6.4) 8.9% (6.5–11.3)
2,133% 1,333% 2,125%
0.0% (0.0–0.0) 0.4% (0.0–0.8) 0.6% (0.1–1.1) 0.0% (0.0–0.0)
0.0% (0.0–0.0) 1.3% (0.6–2.0) 0.5% (0.1–0.9) 0.4% (0.0–1.0)
3.4% (0.8–6.0) 1.7% (0.8–2.6) 1.9% (1.1–2.7) 0.7% (0.1–1.3)
14.2% (10.4–18.0) 8.6% (7.0–10.2) 5.5% (4.1–6.9) 1.2% (0.2–2.2)
n/a 2,050% 817% n/a
0.2% (0.0–0.4) 0.5% (0.2–0.8)
1.2% (0.6–1.8) 0.4% (0.1–0.7)
1.8% (1.1–2.5) 1.7% (1.1–2.3)
7.1% (5.8–8.4) 6.6% (5.4–7.8)
3,450% 1,220%
0.3% (0.0–0.9) 0.4% (0.0–0.8) 0.4% (0.0–0.8) 0.2% (0.0–0.5)
1.9% (0.4–3.4) 0.4% (0.0–0.8) 0.7% (0.2–1.2) 0.9% (0.3–1.5)
0.8% (0.0–1.9) 1.3% (0.5–2.1) 3.3% (2.1–4.5) 1.0% (0.4–1.6)
10.7% (7.0–14.4) 7.7% (5.9–9.5) 10.6% (8.6–12.6) 2.2% (1.3–3.1)
3,467% 1,825% 2,550% 1,000%
Table 4. Logistic Regression, Electronic Cigarette Use, 2013
Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High school Some college College degree
Ever use overall (n = 3,081)
Current use overall (n = 3,081)
REF 6.4 (4.4–9.2) 26.9 (17.0–42.5) 45.2 (30.7–66.4)
REF 5.8 (3.4–10.0) 37.6 (21.1–67.0) 38.6 (23.0–64.7)
REF 1.0 (0.7–1.6) 1.8 (1.3–2.7) 1.8 (1.2–2.8)
REF 1.1 (0.6–1.8) 1.9 (1.1–3.1) 1.1 (0.6–2.0)
1.1 (0.7–1.7) REF 0.8 (0.5–1.3)
1.8 (1.0–3.3) REF 1.5 (0.7–3.0)
12.4 (6.8–22.6) 4.8 (2.9–7.9) 2.8 (1.7–4.6) REF
24.0 (9.1–63.2) 8.2 (3.4–20.1) 4.4 (1.8–10.9) REF
0.9 (0.7–1.2) REF
0.8 (0.6–1.2) REF
1.6 (1.0–2.6) 1.4 (0.9–2.0) 2.3 (1.6–3.3) REF
2.6 (1.4–4.8) 1.5 (0.9–2.6) 3.2 (2.0–5.4) REF
surveys in order to create a pooled data set to test the interactions between year and demographics. However, increases in ever use appeared highest for nonsmokers, young adults, adults with lower levels of education, and adults in the South Census region. Increases in current use appeared the highest for young adults, males, adults in the South Census region, and adults with less than a high school degree.
Ever and Current Electronic Cigarette Use, 2013 Daily smokers (54.2%) and nondaily smokers (47.0%) were the most likely to have tried electronic cigarettes. However, a nontrivial amount of nonsmokers had also tried these products, former smokers (13.5%) and never-smokers (3.5%). Adults aged 18–25 (21.0%), aged 25–44 (15.7%) and aged 45–64 (12.2%) compared to older adults (65 and older) (4.8%) were more likely to have tried electronic cigarettes. Ever use of electronic cigarettes also varied by race and education status (Table 2). Almost half of adults who have tried electronic cigarettes report current use (Table 3). Use is highest among daily smokers (34.1%) and nondaily smokers (30.3%), compared to former smokers (5.4%) and never-smokers (1.4%). Younger adults (ages 18–24) are more likely to report use than older adults. In multivariable analysis, current daily, nondaily, and former smoking status remained significant predictors of ever and current use, as did race, age, and education. White adults were more likely than black adults, younger adults were more likely than older adults, and adults with some college education were more likely than adults with a college degree to have tried electronic cigarettes (Table 4).
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Overall Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High School Some college College degree
2010, % (95% CI) (unweighted n = 3,240)
6
Current Use among Nonsmokers Despite our finding that current use prevalence is substantially higher among current smokers that adults who have never smoked cigarettes or who have successfully quit smoking cigarettes, almost a third of current electronic cigarette users are either never-smokers (12.6%) or former smokers (19.9%). However, it is possible that some former smokers used these products as a form of nicotine replacement therapy to help them quit. To address this possibility, we examined use among only never-smokers and former smokers who quit more than five years ago (distant former smokers). Note that electronic cigarettes were not available on the U.S. market prior to 2007. After removing recent former smokers from our analyses, we found that two out of 10 current electronic cigarette users are neversmokers (12.6%) or distant former smokers (5.8%). Two thirds of current users are either current smokers (67.4%) or recent former smokers (14.1%).
We examined possible mode effects by using cross-tabulations to compare electronic cigarette variables across the RDD and probability-based panel frames. There were no statistically significant mode differences in these variables for years 2010 to 2012. In 2013, respondents in the RDD frame (84.7%) were more likely to have heard of electronic cigarettes than those in the probability-based panel frame (79.6%), p = .001; however, there were no statistically significant differences across frames for ever use (12.1% vs. 13.6%) or current use (6.3% vs. 7.2%).
Discussion Electronic cigarettes entered the U.S. market in 2007, and to date, the FDA Center for Tobacco Products has not finalized its deeming rule for exerting jurisdiction over tobacco products to include these products. Our study demonstrated rapid growth in electronic cigarette use among U.S. adults from 2010 to 2013. We observed statistically significant increases across all levels of smoking status, region, race, age, sex, and education. Although the magnitude varied across demographic groups, the increase in ever use was especially high among young adults and adults with lower levels of education. Taken in consideration with previous prevalence studies,3,35,36 our findings suggest a continued growth trend in the use of electronic cigarettes. Each of these previous studies produced estimates for prevalence of ever use in 2010 similar to those presented in this paper. Moreover, two studies that examined two years of data found rapid growth in use. One study found ever use quadrupled from 2009 to 2010,36 while another found ever use almost doubled from 2010 to 2011.3 Collectively, these studies and recent financial analyses predicting rapid growth37,43,44 help to explain how estimates for the prevalence of use has risen so sharply since the last published U.S. prevalence estimates. The rapid growth experience in the United States is similar to that in other countries that permit electronic cigarette use. Ever and current use in Great Britain more than doubled from 2010 to 2012 for both occasional and daily smokers.45 National regulatory policy also seems to affect electronic cigarette use. An international survey administered to current and recent former tobacco users between July 2010 and June yielded estimates for ever and current use in the United States and United Kingdom that were higher than those for Australia and Canada.4 At the time of this study, the latter two countries had greater restrictions on the sale of nicotine-containing electronic cigarettes.
Consistent with previous research,3,35,36 we found the use of electronic cigarettes varied by cigarette smoking status. Current smokers were more likely than never- and former smokers to have tried electronic cigarettes. Although smokers are most likely to use these products, almost a third of current users are nonsmokers, suggesting these products contribute to primary nicotine addiction and to renormalization of tobacco use. Consideration of potential harm reduction benefits of e-cigarettes should be balanced against this finding. The rapid growth in use of electronic cigarettes highlights several additional reasons for concern. First, use of electronic cigarettes among current smokers may put them at risk for maintaining their dependence through the use of multiple forms of nicotine delivery products. Second, more research is needed regarding the possibility of relapse to nicotine addiction, and perhaps to combustible cigarette re-use, among former smokers who use electronic cigarettes. Third, use of electronic cigarettes continues to increase at substantial rates. Sales of electronic cigarettes have doubled every year since 2008, sales in 2013 are projected to reach $1.7 billion.46 This trend is of concern given the lack of regulation of these products. Until the FDA finalizes (and strengthens) its deeming rule for exerting its regulatory authority over electronic cigarettes, safety and health risks will increase as more people use these products. Safety issues arise from potentially defective battery powered heating elements, leaking spent nicotine cartridges,23 and nicotine poisoning in young children. Nicotine in electronic cigarettes may pose a greater poisoning risk than leaf tobacco.29 Electronic cigarette cartridges typically contain up to 20 mg of nicotine, while the estimated lethal dose of nicotine for a child as little as 10 mg.2 A recent study on unintentional nicotine poisonings among children under the age of six found a total of 13,705 product ingestions cases,47 while the National Poison Data System reports a 208% increase from 2012 to 2013 in liquid nicotine reported exposures to poison centers.48 Increased usage over the past three years suggests greater risk of poisoning and the need for safety and child-proofing regulations for these potentially lethal products. Finally, the proposed FDA deeming rule does not include restrictions on marketing of electronic cigarettes. This regulatory gap is alarming in light of recent research indicating that cigarette smokers were receptive to television ads and reported to intentions to use electronic cigarettes after viewing an ad that has been televised on numerous U.S. cable networks.49 This study has at least four limitations. First, our dual frame methodology is designed to reduce the potential for sample bias associated with either RDD or internet panel samples alone, but we still can’t eliminate the potential for noncoverage bias. Also, the use of the internet panel raises some concern about the representativeness of the sample. However, several studies demonstrate that this probability-based panel can produce results similar to well-designed RDD surveys50,51 and our use of this dual frame methodology produced estimates for current smoking that did not differ from those of several large, government surveys of U.S. adults.52 Second, these data are self-report and cross-sectional, and we could not verify that responses concerning cigarette smoking and electronic cigarette use were not biased. Studies comparing self-reported and biochemically assessed cigarette smoking, however, have supported the validity of self-reported cigarette smoking.53 To our knowledge, the validity of self-reported electronic cigarette use has not been assessed. Third, we did find evidence of a mode effect for awareness of electronic cigarettes in 2013. However, responses were consistent across modes in previous years and there were no differences in ever or current use in 2013. Fourth, the construct we used to examine the role e-cigarettes
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Mode Effects
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Funding The authors are supported by the American Academy of Pediatrics Julius B. Richmond Center of Excellence. Support for this article has been provided in part by Legacy (6033) and the Flight Attendant Medical Research Institute (052302). The information, views, and opinions contained herein are those of the authors and do not necessarily reflect the views and opinions of Legacy or the Flight Attendant Medical Research Institute.
Declaration of Interests None declared.
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11. Schober W, Szendrei K, Matzen W, et al. Use of electronic cigarettes (e-cigarettes) impairs indoor air quality and increases feno levels of e-cigarette consumers. Int J Hyg Environ Health. 2013;217:628–637. 12. Schripp T, Markewitz D, Uhde E, Salthammer T. Does e-cigarette consumption cause passive vaping? Indoor Air. 2013;23:25–31. 13. Bullen C, Howe C, Laugesen M, et al. Electronic cigarettes for smoking cessation: A randomised controlled trial. Lancet. 2013;382:1629–1637. 14. Vickerman KA, Carpenter KM, Altman T, Nash CM, Zbikowski SM. Use of electronic cigarettes among state tobacco cessation quitline callers. Nicotine Tob Res. 2013;15:1787–1791. 15. Grana RA, Popova L, Ling PM. A longitudinal analysis of electronic cigarette use and smoking cessation. JAMA Intern Med. 2014;174:812–813. 16. Popova L, Ling PM. Alternative tobacco product use and smoking cessation: a national study. Am J Public Health. 2013;103:923–930. 17. German Cancer Research Center, Heidelberg. Electronic cigarettes--an overview. 2013. http://www.dkfz.de/en/presse/download/RS-Vol19-E-CigarettesEN.pdf. Accessed October 21, 2014. 18. Cameron JM, Howell DN, White JR, Andrenyak DM, Layton ME, Roll JM. Variable and potentially fatal amounts of nicotine in e-cigarette nicotine solutions. Tob Control. 2013;1–2. 19. Cheah NP, Chong NW, Tan J, Morsed FA, Yee SK. Electronic nicotine delivery systems: regulatory and safety challenges: Singapore perspective. Tob Control. 2012;1–7. 20. Cobb NK, Brookover J, Cobb CO. Forensic analysis of online marketing for electronic nicotine delivery systems. Tob Control. 2013;1–4. 21. Eissenberg T. Electronic nicotine delivery devices: ineffective nicotine delivery and craving suppression after acute administration. Tob Control. 2010;19:87–88. 22. Trehy ML, Ye W, Hadwiger ME, et al. Analysis of electronic cigarette cartridges, refill solutions, and smoke for nicotine and nicotine related impurities. J Liq Chromatogr R T. 2011;34:1442–1458. 23. Trtchounian A, Talbot P. Electronic nicotine delivery systems: is there a need for regulation? Tob Control. 2011;20:47–52. 24. Williams M, Talbot P. Variability among electronic cigarettes in the pressure drop, airflow rate, and aerosol production. Nicotine Tob Res. 2011;13:1276–1283. 25. Ayers JW, Ribisl KM, Brownstein JS. Tracking the rise in popularity of electronic nicotine delivery systems (electronic cigarettes) using search query surveillance. Am J Prev Med. 2011;40:448–453. 26. Noel J, Rees V, Connolly G. Electronic cigarettes: a new ‘tobacco’ industry? Tob Control. 2010;20:1–2. 27. Yamin CK, Bitton A, Bates DW. E-cigarettes: a rapidly growing Internet phenomenon. Ann Intern Med. 2010;153:607–609. 28. American Cancer Society. Restrict the sale of electronic cigarettes. 2013. http://www.cancer.org/myacs/eastern/areahighlights/cancernynj-newsny-ecig-health-vote. Accessed October 21, 2014. 29. Cobb NK, Byron MJ, Abrams D, Shields PG. Novel nicotine delivery systems and public health: the rise of the “e-cigarette”. Am J Public Health. 2010;100:2340–2342. 30. Henningfield JE, Zaatari GS. Electronic nicotine delivery systems: emerging science foundation for policy. Tob Control. 2010;19:89–90. 31. McInerny T, Wimmer H, Henley D, et al. Letter to president Obama from health organizations requesting FDA regulation of e-cigarettes. 2013. http://www2.aap.org/richmondcenter/pdfs/Sept2013letterECigs.pdf. Accessed October 21, 2014. 32. National Association of Attorneys General. Letter to the honorable Margaret Hamburg. 2013. http://www.naag.org/assets/files/pdf/E%20 Cigarette%20Final%20Letter%20(5)(1).pdf. Accessed October 21, 2014. 33. Centers for Disease Control and Prevention. Notes from the field: electronic cigarette use among middle and high school students - United States, 2011–2012. MMWR. Morb Mortal Wkly Rep. 2013;62:729–730. 34. McMillen R, Maduka J, Winickoff J. Use of emerging tobacco products in the united states. J Environ Public Health. 2012;2012:1–8. 35. Pearson JL, Richardson A, Niaura RS, Vallone DM, Abrams DB. E-Cigarette awareness, use, and harm perceptions in US adults. Am J Public Health. 2012;102:1758–1766.
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may have had in the former smokers’ quit attempts is rather crude. Use by former smokers to quit smoking has different implications than use by former smokers who are reinitiating nicotine use (and possibly addiction). Although our data suggest that at least 40% of former smokers are reinitiating their tobacco use, a more refined construct would provide more confidence in this finding. In conclusion, there has been rapid growth in ever and current electronic cigarette use over the past four years, especially among young adults. Use is highest among young adults and current cigarette smokers. Although smokers are most likely to use these products, almost a third of current users are nonsmokers, suggesting that electronic cigarettes contribute to primary nicotine addiction and to renormalization of smoking behaviors. As Popova and Ling note,16 smoking rates decreased due to health concerns, regulatory and taxation burden, and the denormalization of smoking behaviors. Given the substantial growth in the use of electronic cigarettes, regulatory action is needed at the federal, state, and local levels to prevent the renormalization of tobacco use to ensure that these products do not contribute to preventable chronic disease.
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45. Dockrell M, Morrison R, Bauld L, McNeill A. E-cigarettes: prevalence and attitudes in Great Britain. Nicotine Tob Res. 2013;15:1737–1744. 46. Elliott S. E-Cigarette makers’ ads echo tobacco’s heyday. New York Times. 2013. http://www.nytimes.com/2013/08/30/business/media/e-cigarette-makers-ads-echo-tobaccos-heyday.html?_r=0&pagewanted=print. Accessed October 21, 2014. 47. Connolly G, Richter P, Aleguas A , Pechacek T, Stanfill S, Alpert H. Unintentional child poisonings through ingestion of conventional and novel tobacco products. Pediatrics. 2010;125:896–899. 48. American Association of Poison Control Centers. E-cigarette devices and liquid nicotine. 2014. http://www.aapcc.org/alerts/e-cigarettes/. Accessed October 21, 2014. 49. Duke JC, Lee YO, Kim AE, et al. Exposure to electronic cigarette television advertisements among youth and young adults. Pediatrics. 2014;134:e29–e36. 50. Chang L, Krosnick JA. National surveys via RDD telephone interviewing versus the internet comparing sample representativeness and response quality. Public Opin Quart. 2009;73:641–678. 51. Yeager DS, Krosnick JA, Chang LC, et al. Comparing the accuracy of RDD telephone surveys and internet surveys conducted with probability and non-probability samples. Public Opin Quart. 2011;75:709–747. 52. McMillen RC, Winickoff JP, Wilson K, Tanski S, Klein JD. A dual-frame sampling methodology to address landline replacement in tobacco control research. Tob Control. 2013;1–4. 53. Caraballo RS, Giovino GA, Pechacek TF. Self-reported cigarette smoking vs. serum cotinine among U.S. adolescents. Nicotine Tob Res. 2004;6:19–25. 54. Bullen C, McRobbie H, Thornley S, Glover M, Lin R, Laugesen M. Effect of an electronic nicotine delivery device (e cigarette) on desire to smoke and withdrawal, user preferences and nicotine delivery: randomised crossover trial. Tob Control. 2010;19:98–103.
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36. Regan AK, Promoff G, Dube SR, Arrazola R. Electronic nicotine delivery systems: adult use and awareness of the ‘e-cigarette’ in the USA. Tob Control. 2013;22:19–23. 37. Burritt C. E-Cigarette pioneers holding breath as big firms invade. 2013. http://www.bloomberg.com/news/2013-06-20/e-cigarette-pioneersholding-breath-as-big-firms-invade-retail.html. Accessed October 21, 2014. 38. Blumberg SJ. Wireless substitution: Early release of estimates from the national health interview survey, January-June 2013. 2013. http:// www.cdc.gov/nchs/data/nhis/earlyrelease/wireless201312.pdf. Accessed October 21, 2014 39. GfK. KnowledgePanel(R) design-summary description. 2013. http:// www.knowledgenetworks.com/knpanel/docs/KnowledgePanel(R)-DesignSummary-Description.pdf. Accessed October 21, 2014. 40. GfK. Methodological papers, presentations, and articles on Knowledge Panel. 2014. http://www.knowledgenetworks.com/ganp/reviewer-info.html. Accessed October 21, 2014. 41. Dennis J. KnowledgePanel: Processes & procedures contributing to sample representativeness & tests for self-selection bias. 2010. http://www.knowledgenetworks.com/ganp/docs/knowledgepanelr-statistical-methods-note. pdf. Accessed October 21, 2014. 42. Callegaro M, Disogra C. Computing response metrics for online panels. Public Opin Quart. 2008;72:1008–1032. 43. Craver R. Electronic cigarettes gaining on traditional products. WinstonSalem Journal. 2012. http://www.journalnow.com/business/business_news/ local/article_41fa04d6-4655-11e2- 95d9-0019bb30f31a.html. Accessed July 11, 2014. 44. Mangan D. E-cigarette sales are smoking hot, set to hit $1.7 billion. CNBC. 2013. http://www.cnbc.com/id/100991511. Accessed July 11, 2014.
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Original investigation
Trends in Electronic Cigarette Use Among U.S. Adults: Use is Increasing in Both Smokers and Nonsmokers Downloaded from http://ntr.oxfordjournals.org/ at University of Manitoba on June 9, 2015
Robert C. McMillen PhD1, Mark A. Gottlieb JD2, Regina M. Whitmore Shaefer MPH3, Jonathan P. Winickoff MD, MPH4, Jonathan D. Klein, MD, MPH3 Department of Psychology, Mississippi State University and American Academy of Pediatrics Julius B. Richmond Center of Excellence, Starkville, MS; 2Public Health Advocacy Institute at Northeastern University School of Law and American Academy of Pediatrics Julius B. Richmond Center of Excellence, Boston, MA; 3American Academy of Pediatrics Julius B. Richmond Center of Excellence, Elk Grove Village, IL; 4Department of General Pediatrics, MGH Center for Child and Adolescent Health Policy and American Academy of Pediatrics Julius B. Richmond Center of Excellence, Boston, MA 1
Corresponding Author: Robert C. McMillen, PhD, Mississippi State University and American Academy of Pediatrics, Julius B. Richmond Center of Excellence, One Research Park, Suite 103, Starkville, MS 39759, USA. Telephone: 662-325-7127; Fax: 663-325-7966; E-mail: [email protected]
Abstract Objectives: We assessed trends in use of electronic cigarettes among U.S. adults, demographic predictors of use, and smoking status of current electronic cigarette users. Methods: Mixed-mode surveys were used to obtain representative, cross-sectional samples of U.S. adults in each of 4 years. Results: Sample sizes for 2010, 2011, 2012, and 2013 were 3,240, 3,097, 3,101, and 3,245, respectively. Ever use of electronic cigarettes increased from 1.8% (2010) to 13.0% (2013), while current use increased from 0.3% to 6.8%, p < .001. Prevalence of use increased significantly across all demographic groups. In 2013, current use among young adults 18–24 (14.2%) was higher than adults 25–44 (8.6%), 45–64 (5.5%), and 65+ (1.2%). Daily smokers (30.3%) and nondaily smokers (34.1%) were the most likely to currently use e-cigarettes, compared to former smokers (5.4%) and never-smokers (1.4%), p < .001. However, 32.5% of current electronic cigarette users are never- or former smokers. Conclusions: There has been rapid growth in ever and current electronic cigarette use over the past 4 years. Use is highest among young adults and current cigarette smokers. Although smokers are most likely to use these products, almost a third of current users are nonsmokers, suggesting that e-cigarettes contribute to primary nicotine addiction and to renormalization of tobacco use. Regulatory action is needed at the federal, state, and local levels to ensure that these products do not contribute to preventable chronic disease.
Introduction Electronic cigarettes entered the U.S. market in 2007, and the affordability, availability, and marketing of these products has increased over the recent years.1 The U.S. Food and Drug Administration (FDA) attempted and failed to regulate these products as drug delivery devices, and thus subject them to the stringent “safe and effective”
standard required for drug approvals.2 The judge stated the FDA has the authority to regulate electronic cigarettes as tobacco products if they choose to do so, but could not regulate them as drugs or drug/ delivery device combination products unless the companies make therapeutic claims or demonstrate they intend their product for a therapeutic purpose. The FDA announced its intention to do so in
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differences in quitting among the randomized groups at six months. Other studies used longitudinal population designs to examine the relationship between e-cigarette use and quitting over one year. Two of these studies found no statistically significant differences in the odds of quitting tobacco cigarettes at one-year follow-up between smokers who had used e-cigarettes at baseline and smokers who had not,4,15,16 whereas the third study found a statistically significantly lower likelihood of quitting among e-cigarette triers compared to non-triers.14 In the absence of sufficient data and FDA regulation, the public health community needs more research on the population prevalence of electronic cigarette use and the characteristics of people who use these products. A recent overview summarizes many of the concerns regarding electronic cigarettes. Broadly, these concerns involve the unknown characteristics of this product, the health effects for users and nonusers exposed to the vapor, the impact of use on cigarette smoking behaviors, the lack of evidence that these products increase efficacy in cigarette smoking cessation, and the lack of any product regulation.17 Specifically, many electronic cigarettes have unknown levels of nicotine, unknown ingredients, technical flaws, and variable quality.2,18–24 Moreover, the known ingredients of electronic cigarettes have not been demonstrated to be safe for humans, when heated to temperatures sufficient to create a vapor. Citing these issues as well as concerns about the rapid growth in market, growth in internet presence and advertising,25–27 and appeal to youth, several scientists and organizations, including the National Association of Attorneys General, have urged the FDA assert their authority over tobacco products to include electronic cigarettes.2,23,28–32 To date, the limited amount of research on the social penetration of electronic cigarettes indicates annual growth in both awareness and use of electronic cigarettes. A recent Centers for Disease Control and Prevention study found an increase in ever use of electronic cigarettes among both U.S. middle and high school students from 2011 to 2012.33 Among U.S. adults, ever use of these products in 2010 ranged from 1.8% to 3.4%,3,34–36 and had increased from 2009.36 Use of these products continued to increase in 2011, with 5.8% of U.S. adults reporting ever use of electronic cigarettes.3 Collectively, these studies illustrate continuous growth in use of these products from 2009 to 2011. Recent financial analyses suggest continued growth in market.37 Not surprisingly use of electronic cigarettes is more common among cigarette smokers and users of other tobacco products than among non-tobacco users.3,34–36 Ever use of these products has also been found to vary by educations status,34,36 income36, and sex36. In summary, the use of electronic cigarettes is expected to be increasing and there is a variability in use prevalence across subpopulations. Although use is substantially higher among smokers than nonsmokers, several studies have found nontrivial levels of use among nonsmokers. The purpose of this study is to assess trends in use of electronic cigarettes among U.S. adults, demographic predictors of use, and smoking status of current electronic cigarette users. Results from this study can inform regulatory decisions about these products, while the identification of potential high risk demographic groups can guide clinical counseling efforts regarding the risks of any tobacco or nicotine use.
Methods Cross-sectional dual-frame surveys representing national probability samples of adults were administered in 2010, 2011, 2012, and 2013. The design included a Random Digit Dialing (RDD) frame and an internet panel frame developed from a probability sample of U.S. adults, in
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April 2011 under its authority provided by the Tobacco Control Act,3 and released a draft of the deeming rule in April 2014. According to proposed deeming rule, makers of newly deemed tobacco products would be required to (a) register with FDA and report product and ingredient listings (but it is not clear if this applies to the FDA or to the consumer), (b) only market new products after FDA review, (c) not distribute free samples, (d) include a health warning label, and (e) restrict sale of electronic cigarettes to adults 18 years of age and older. The draft does not eliminate online sales, eliminate flavors, address child safety issues, or regulate or limit marketing. The comment period for this deeming rule expires in August 2014 and the FDA anticipates a final action in June 2015. The proposed regulatory oversight on electronic cigarettes is lighter in the United States than for much of the global community. These products are not currently legal in Brazil and Singapore; and Canada and Australia restrict the sale of nicotine containing electronic cigarettes to products that have been submitted to and approved by their medicine regulatory agencies.4,5 In Europe, the restrictions and regulations also differ from the United States. The European Union approved new rules in February 2014 that will ban electronic cigarette advertising, the products will have to be childproof, packages will have to have safety warnings, and the dosage will be limited to 20 mg of nicotine. These regulations are scheduled to be implemented in 2016.6 Currently, there are several gaps in regulation of electronic cigarettes. Neither the FDA nor the Consumer Product Safety Commission oversees the safety and manufacturing of these products. Marketing of electronic cigarettes is regulated by general advertising rules, but not the additional regulations that apply to cigarettes and smokeless tobacco. Although federal law has prohibited tobacco advertisements on television and radio since 1972, these venues are now home to advertisements for electronic cigarettes.7 These products do not meet many states’ definition of tobacco products, and thus tobacco taxation rates and age of purchase requirements do not apply in these states. Although three states and 188 communities include the restriction of electronic cigarettes use in their comprehensive smokefree policies,8 many state and local smokefree laws predate the development of electronic cigarettes. Thus the use of electronic cigarettes is still permissible in many places in which combustible tobacco products are prohibited. The unknown risks of electronic cigarettes are likely to be less harmful than combustible cigarettes. Although research on the harms of secondhand vapor is limited, electronic cigarettes can produce volatile organic compounds, heavy metals, and other toxins in the vapor released, albeit in lower levels than combustible tobacco.9–12 Harm reduction proponents highlight this decreased risk, and view electronic cigarettes as means to reduce exposure to combustible tobacco, and perhaps even as a cessation tool for smokers.13 There are, however, some important possibilities to consider. Specifically, electronic cigarettes could contribute to primary nicotine addiction among youth and young adults and to renormalization of smoking behaviors. Moreover, use of electronic cigarettes by smokers who are motivated to quit and are strong candidates for evidence-based smoking cessation treatment may complicate treatment because electronic cigarettes are not approved nor incorporated into clinical practice guidelines. Although many cigarette smokers who have tried electronic cigarettes report doing so as a strategy for quitting smoking,4,14 the limited number of studies examining use of electronic cigarettes and cessation have not supported this strategy. Bullen13 tested the effectiveness of e-cigarettes for cessation by randomly assigning smokers to use e-cigarettes or the nicotine patch; and found no statistically significant
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Self-Reported Use of Electronic Cigarettes Respondents were asked “Have you ever heard of a product called electronic cigarettes or e-cigarettes, or brands such as Smoking Everywhere, NJOY, Blu, or others?” Respondents who had heard of electronic cigarettes were asked, “Have you tried Electronic Cigarettes or E-cigarettes, even just one time?” Respondents who reported yes were classified as having tried electronic cigarettes. Those who had tried electronic cigarettes were asked, “Do you now use e-cigarettes every day, some days, or not at all.” Respondents who reported every day or some days were classified as current users.
Self-Reported Smoking Respondents were asked, “Have you smoked at least 100 cigarettes in your entire life?” Respondents who reported that they had were then asked, “Do you now smoke cigarettes every day, some days, or not at all?” Respondents who reported that they have smoked at least 100 cigarettes and now smoke every day or some days were categorized as current smokers, while those who reported not at all were categorized as former smokers. Former smokers were asked, “About how long has it been since you last smoked cigarettes regularly?” In analyses of electronic cigarette use among never- and former smokers, former smokers who had quit smoking less than five years ago were considered to be recent former smokers and those who had quit more than five years ago (and before electronic cigarettes entered the U.S. market) were considered to distant former smokers.
Analyses Data for overall and subpopulation ever and current use of electronic cigarettes were examined to assess three year trends from 2010 to 2013. Using 2013 data, we examined demographic factors associated with electronic cigarette with multivariable logistic regression and examined nonsmokers’ contribution to the electronic
cigarette market. Finally, bivariate analyses were applied compared current electronic use among never-smokers, former smokers, and current smokers.
Results Sample Characteristics Table 1 shows the demographic characteristics of the overall sample. 2010 In the RDD frame, of 2,128 eligible respondents contacted, 1,504 (70.7%) completed surveys. For the internet panel frame, 2,272 panelists were randomly drawn from the probability panel; 1,736 responded to the invitation, yielding a final stage completion rate of 67.5%.42 Length of time on the panel for the internet panel frame ranged from 0.09 to 11.08 years, with a median length of time on the panel of 2.29 years. The total sample size was 3,240. 2011 In the RDD frame, of 2,282 eligible respondents contacted, 1,500 (63%) completed surveys. For the probability-based panel frame, 2,476 panelists were randomly drawn from the probability panel; 1,597 responded to the invitation, yielding a final stage completion rate of 65%. Length of time on the panel for the probability-based panel frame ranged from 0.18 to 11.93 years, with a median length of time on the panel of 1.4 years. The total sample size was 3,097. 2012 In the RDD frame, of 1,713 eligible respondents contacted, 1,507 (88.0%) completed surveys. For the probability-based panel frame, 2,529 panelists were randomly drawn from the probability panel; 1,594 responded to the invitation, yielding a final stage completion rate of 63%. Length of time on the panel for the probability-based panel frame ranged from 0.06 to 12.89 years, with a median length of time on the panel of 1.48 years. The total sample size was 3,101. 2013 In the RDD frame, of 1,689 eligible respondents contacted, 1,552 (91.9%) completed surveys. For the probability-based panel frame, 2,667 panelists were randomly drawn from the probability panel; 1,693 responded to the invitation, yielding a final stage completion rate of 63.5%. Length of time on the panel for the probability-based panel frame ranged from 0.12 to 13.97 years, with a median length of time on the panel of 2.16 years. The total sample size was 3,245.
Trends In weighted analysis, ever use of electronic cigarettes increased from 1.8% to 13.0% (Table 2). Among subpopulations, ever use also increased significantly across all assessed groups over the four year period (p < .05 for all comparisons). Although nondaily smokers and daily smokers had the highest absolute increases in ever use of electronic cigarettes, use among never- and former smokers also increased. Current use also demonstrated substantial growth; prevalence increased from 0.3% in 2010 to 6.8% in 2013. Table 3 summarizes subpopulation trends. Overall, ever use of electronic cigarettes increased by 622% (Table 2) and current use increased by 2,167% (Table 3) from 2010 to 2013. Increases in use were substantial across all demographic groups. We did not reweight the data from the four cross-sectional
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order to reduce non-coverage issues arising from wireless substitution. Wireless substitution of cell phones for landlines continues to increase, and 39.4% of U.S. households are currently wireless only.38 The RDD frame included households with listed and unlisted landline telephones; five attempts were made to contact those selected adults who were not home. The Survey Research Laboratory at Mississippi State University’s Social Science Research Center administered the surveys via computer-assisted telephone interviews to respondents in this frame. The probability-based panel frame included an online survey conducted by Knowledge Networks, administered to a randomly selected sample from a nationally representative research panel.39,40 This panel is based on a sampling frame which includes both listed and unlisted numbers, those without a landline telephone, and does not accept self-selected volunteers,39,40 and provides sample coverage for 99% of U.S. households.41 Surveys were administered to both frames from October to November in 2010, 2011, 2012, and 2013. The Institutional Review Board (IRB) at Mississippi State University approved this study. For the RDD frame, informed verbal consent was obtained and the IRB provided a waiver of documentation of the written consent process. For the probability-based panel frame, participants were presented with an informed consent statement, and clicked continue if they agreed to participate. More detailed methods have been previously published.34 Within each year, data were weighted to adjust for age, race, sex, and region, as well as frame overlap among internet panel respondents who also had a landline telephone and were therefore also eligible for the RDD frame.
3
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4 Table 1. Weighted Sample Characteristics 2011 (unweighted n = 3,097)
2012 (unweighted n = 3,101)
2013 (unweighted n = 3,245)
56.9% 24.8% 4.6% 13.7%
56.9% 25.0% 3.4% 14.7%
59.6% 24.8% 3.8% 11.8%
59.9% 24.6% 4.3% 10.1%
12.6% 18.4% 37.6% 31.4%
12.9% 18.9% 37.2% 31.0%
17.8% 21.7% 37.5% 23.0%
17.3% 22.1% 37.8% 22.2%
74.2% 11.5% 14.3%
69.5% 11.3% 19.2%
71.5% 11.4% 17.1%
70.3% 11.3% 17.5%
13.7% 38.8% 33.3% 14.2%
9.3% 39.7% 34.9% 16.1%
11.4% 38.3% 34.7% 15.6%
10.7% 37.3% 34.3% 16.2%
47.6% 52.4%
48.3% 51.7%
48.1% 51.9%
47.4% 52.6%
9.2% 28.5% 29.3% 33.0%
10.5% 27.3% 29.6% 32.6%
9.9% 28.8% 28.1% 33.4%
9.0% 26.9% 28.9% 34.9%
Table 2. Prevalence of Electronic Cigarette Ever Use 2010, % (95% CI) 2011, % (95% CI) 2012, % (95% CI) 2013, % (95% CI) Relative percent change, (unweighted n = 3,240) (unweighted n = 3,097) (unweighted n = 3,101) (unweighted n = 3,245) 2010–2013 Overall Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High school Some college College degree
1.8 (1.3–2.3)
7.3 (6.4–8.2)
10.6 (9.5–11.7)
13.0 (11.8–14.2)
622%
0.3 (0.0–0.6 1.5 (0.7–2.3) 8.2 (2.6–13.8) 6.2 (4.0–8.4)
1.2 (0.7–1.7) 6.5 (4.8–8.2) 13.9 (6.5–21.3) 30.9 (26.4–35.4)
2.4 (1.7–3.1) 11.7 (9.5–13.9) 27.1 (18.3–35.9) 44.6 (39.3–49.9)
3.5 (2.7–4.3) 13.5 (11.1–15.9) 47.0 (38.5–55.5) 54.2 (48.7–59.7)
1,067% 800% 473% 774%
2.7 (1.4–4.0) 1.4 (0.6–2.2) 1.6 (0.9–2.3) 1.9 (0.8–3.0)
4.8 (3.0–6.6) 7.8 (5.9–9.7) 7.0 (5.5–8.5) 8.2 (6.1–10.3)
8.9 (6.5–11.3) 12.9 (10.5–15.3) 10.0 (8.3–11.7) 10.6 (8.2–13.0)
10.1 (7.5–12.7) 11.6 (9.2–14.0) 14.9 (12.9–16.9) 14.1 (11.5–16.7)
274% 729% 831% 642%
1.7 (1.2–2.2) 1.9 (0.3–3.5) 1.8 (0.4–3.2)
8.3 (7.2–9.4) 3.7 (1.7–5.7) 5.6 (3.4–7.8)
12.3 (11.0–13.6) 5.3 (2.8–7.8) 7.3 (4.7–9.9)
13.1 (11.7–14.5) 11.5 (8.1–14.9) 14.0 (11.1–16.9)
385% 721% 775%
2.5 (0.6–4.4) 2.1 (1.2–3.0) 1.6 (0.9–2.3) 0.4 (0.0–0.9)
7.3 (4.5–10.1) 10.7 (8.4–13.0) 4.9 (3.6–6.2) 4.4 (3.1–5.7)
15.0 (9.9–20.1) 13.9 (11.6–16.2) 9.6 (7.9–11.3) 2.3 (1.3–3.3)
21.0 (16.6–25.4) 15.7 (13.6–17.8) 12.2 (10.2–14.2) 4.8 (2.9–6.7)
1,005% 824% 542% 167%
2.2 (1.4–3.0) 1.4 (0.9–1.9)
8.8 (7.3–10.3) 5.8 (4.7–6.9)
11.1 (9.4–12.8) 10.1 (8.7–11.5)
13.9 (12.1–15.7) 12.4 (10.8–14.0)
456% 490%
0.7 (0.0–1.7) 1.7 (0.9–2.5) 3.7 (2.4–5.0) 0.5 (0.1–0.9)
11.6 (7.8–15.4) 7.5 (5.8–9.2) 8.3 (6.5–10.1) 4.8 (3.5–6.1)
8.5 (5.2–11.8) 14.0 (11.7–16.3) 13.9 (11.6–16.2) 5.6 (4.3–6.9)
16.9 (12.4–21.4) 14.9 (12.5–17.3) 18.9 (16.3–21.5) 6.2 (4.8–7.6)
956% 3,625% 759% 343%
Note. CI = confidence interval.
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Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High school Some college College degree
2010 (unweighted n = 3,240)
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5
Table 3. Prevalence of Electronic Cigarette Current Use 2011, % (95% CI) 2012, % (95% CI) 2013, % (95% CI) (unweighted n = 3,097) (unweighted n = 3,101) (unweighted n = 3,245)
Relative percent change, 2010–2013
0.3% (0.1–0.5)
0.8% (0.5–1.1)
2.6% (2.0–3.2)
6.8% (5.9–7.7)
2,167%
0.1% (0.0–0.2) 0.3% (0.0–0.7) 1.4% (0.0–3.3) 1.4% (0.3–2.5)
0.1% (0.0–0.2) 0.1% (0.0–0.3) 1.0% (0.0–2.9) 5.0% (3.0–7.0)
0.1% (0.0–0.2) 1.1% (0.4–1.8) 3.1% (0.0–6.5) 10.8% (7.5–14.1)
1.4% (0.9–1.9) 5.4% (3.8–7.0) 34.1% (26.0–42.2) 30.3% (25.2–35.4)
1,300% 1,700% 2,336% 2,064%
0.5% (0.0–1.2) 0.3% (0.0–0.7) 0.2% (0.0–0.5) 0.3% (0.0–0.6)
0.3% (0.0–0.8) 0.5% (0.0–1.1) 0.4% (0.0–0.8) 1.7% (0.9–2.5)
1.5% (0.5–2.5) 2.3% (1.2–3.4) 1.4% (0.7–2.1) 2.0% (0.9–3.1)
5.5% (3.6–7.4) 6.3% (4.5–8.1) 8.3% (6.7–9.9) 6.0% (4.2–7.8)
1,000% 2,000% 4,050% 1,900%
0.3% (0.1–0.5) 0.3% (0.0–0.9) 0.4% (0.0–1.0)
0.8% (0.4–1.2) 0.6% (0.0–1.4) 1.0% (0.2–1.8)
1.9% (1.4–2.4) 0.3% (0.0–0.9) 2.1% (0.7–3.5)
6.7% (5.6–7.8) 4.3% (2.2–6.4) 8.9% (6.5–11.3)
2,133% 1,333% 2,125%
0.0% (0.0–0.0) 0.4% (0.0–0.8) 0.6% (0.1–1.1) 0.0% (0.0–0.0)
0.0% (0.0–0.0) 1.3% (0.6–2.0) 0.5% (0.1–0.9) 0.4% (0.0–1.0)
3.4% (0.8–6.0) 1.7% (0.8–2.6) 1.9% (1.1–2.7) 0.7% (0.1–1.3)
14.2% (10.4–18.0) 8.6% (7.0–10.2) 5.5% (4.1–6.9) 1.2% (0.2–2.2)
n/a 2,050% 817% n/a
0.2% (0.0–0.4) 0.5% (0.2–0.8)
1.2% (0.6–1.8) 0.4% (0.1–0.7)
1.8% (1.1–2.5) 1.7% (1.1–2.3)
7.1% (5.8–8.4) 6.6% (5.4–7.8)
3,450% 1,220%
0.3% (0.0–0.9) 0.4% (0.0–0.8) 0.4% (0.0–0.8) 0.2% (0.0–0.5)
1.9% (0.4–3.4) 0.4% (0.0–0.8) 0.7% (0.2–1.2) 0.9% (0.3–1.5)
0.8% (0.0–1.9) 1.3% (0.5–2.1) 3.3% (2.1–4.5) 1.0% (0.4–1.6)
10.7% (7.0–14.4) 7.7% (5.9–9.5) 10.6% (8.6–12.6) 2.2% (1.3–3.1)
3,467% 1,825% 2,550% 1,000%
Table 4. Logistic Regression, Electronic Cigarette Use, 2013
Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High school Some college College degree
Ever use overall (n = 3,081)
Current use overall (n = 3,081)
REF 6.4 (4.4–9.2) 26.9 (17.0–42.5) 45.2 (30.7–66.4)
REF 5.8 (3.4–10.0) 37.6 (21.1–67.0) 38.6 (23.0–64.7)
REF 1.0 (0.7–1.6) 1.8 (1.3–2.7) 1.8 (1.2–2.8)
REF 1.1 (0.6–1.8) 1.9 (1.1–3.1) 1.1 (0.6–2.0)
1.1 (0.7–1.7) REF 0.8 (0.5–1.3)
1.8 (1.0–3.3) REF 1.5 (0.7–3.0)
12.4 (6.8–22.6) 4.8 (2.9–7.9) 2.8 (1.7–4.6) REF
24.0 (9.1–63.2) 8.2 (3.4–20.1) 4.4 (1.8–10.9) REF
0.9 (0.7–1.2) REF
0.8 (0.6–1.2) REF
1.6 (1.0–2.6) 1.4 (0.9–2.0) 2.3 (1.6–3.3) REF
2.6 (1.4–4.8) 1.5 (0.9–2.6) 3.2 (2.0–5.4) REF
surveys in order to create a pooled data set to test the interactions between year and demographics. However, increases in ever use appeared highest for nonsmokers, young adults, adults with lower levels of education, and adults in the South Census region. Increases in current use appeared the highest for young adults, males, adults in the South Census region, and adults with less than a high school degree.
Ever and Current Electronic Cigarette Use, 2013 Daily smokers (54.2%) and nondaily smokers (47.0%) were the most likely to have tried electronic cigarettes. However, a nontrivial amount of nonsmokers had also tried these products, former smokers (13.5%) and never-smokers (3.5%). Adults aged 18–25 (21.0%), aged 25–44 (15.7%) and aged 45–64 (12.2%) compared to older adults (65 and older) (4.8%) were more likely to have tried electronic cigarettes. Ever use of electronic cigarettes also varied by race and education status (Table 2). Almost half of adults who have tried electronic cigarettes report current use (Table 3). Use is highest among daily smokers (34.1%) and nondaily smokers (30.3%), compared to former smokers (5.4%) and never-smokers (1.4%). Younger adults (ages 18–24) are more likely to report use than older adults. In multivariable analysis, current daily, nondaily, and former smoking status remained significant predictors of ever and current use, as did race, age, and education. White adults were more likely than black adults, younger adults were more likely than older adults, and adults with some college education were more likely than adults with a college degree to have tried electronic cigarettes (Table 4).
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Overall Smoking status Never-smokers Former smokers Nondaily smokers Daily smokers Region Northeast Midwest South West Race White Black Other Age 18–24 25–44 45–64 65+ Sex Males Females Education Less than high school High School Some college College degree
2010, % (95% CI) (unweighted n = 3,240)
6
Current Use among Nonsmokers Despite our finding that current use prevalence is substantially higher among current smokers that adults who have never smoked cigarettes or who have successfully quit smoking cigarettes, almost a third of current electronic cigarette users are either never-smokers (12.6%) or former smokers (19.9%). However, it is possible that some former smokers used these products as a form of nicotine replacement therapy to help them quit. To address this possibility, we examined use among only never-smokers and former smokers who quit more than five years ago (distant former smokers). Note that electronic cigarettes were not available on the U.S. market prior to 2007. After removing recent former smokers from our analyses, we found that two out of 10 current electronic cigarette users are neversmokers (12.6%) or distant former smokers (5.8%). Two thirds of current users are either current smokers (67.4%) or recent former smokers (14.1%).
We examined possible mode effects by using cross-tabulations to compare electronic cigarette variables across the RDD and probability-based panel frames. There were no statistically significant mode differences in these variables for years 2010 to 2012. In 2013, respondents in the RDD frame (84.7%) were more likely to have heard of electronic cigarettes than those in the probability-based panel frame (79.6%), p = .001; however, there were no statistically significant differences across frames for ever use (12.1% vs. 13.6%) or current use (6.3% vs. 7.2%).
Discussion Electronic cigarettes entered the U.S. market in 2007, and to date, the FDA Center for Tobacco Products has not finalized its deeming rule for exerting jurisdiction over tobacco products to include these products. Our study demonstrated rapid growth in electronic cigarette use among U.S. adults from 2010 to 2013. We observed statistically significant increases across all levels of smoking status, region, race, age, sex, and education. Although the magnitude varied across demographic groups, the increase in ever use was especially high among young adults and adults with lower levels of education. Taken in consideration with previous prevalence studies,3,35,36 our findings suggest a continued growth trend in the use of electronic cigarettes. Each of these previous studies produced estimates for prevalence of ever use in 2010 similar to those presented in this paper. Moreover, two studies that examined two years of data found rapid growth in use. One study found ever use quadrupled from 2009 to 2010,36 while another found ever use almost doubled from 2010 to 2011.3 Collectively, these studies and recent financial analyses predicting rapid growth37,43,44 help to explain how estimates for the prevalence of use has risen so sharply since the last published U.S. prevalence estimates. The rapid growth experience in the United States is similar to that in other countries that permit electronic cigarette use. Ever and current use in Great Britain more than doubled from 2010 to 2012 for both occasional and daily smokers.45 National regulatory policy also seems to affect electronic cigarette use. An international survey administered to current and recent former tobacco users between July 2010 and June yielded estimates for ever and current use in the United States and United Kingdom that were higher than those for Australia and Canada.4 At the time of this study, the latter two countries had greater restrictions on the sale of nicotine-containing electronic cigarettes.
Consistent with previous research,3,35,36 we found the use of electronic cigarettes varied by cigarette smoking status. Current smokers were more likely than never- and former smokers to have tried electronic cigarettes. Although smokers are most likely to use these products, almost a third of current users are nonsmokers, suggesting these products contribute to primary nicotine addiction and to renormalization of tobacco use. Consideration of potential harm reduction benefits of e-cigarettes should be balanced against this finding. The rapid growth in use of electronic cigarettes highlights several additional reasons for concern. First, use of electronic cigarettes among current smokers may put them at risk for maintaining their dependence through the use of multiple forms of nicotine delivery products. Second, more research is needed regarding the possibility of relapse to nicotine addiction, and perhaps to combustible cigarette re-use, among former smokers who use electronic cigarettes. Third, use of electronic cigarettes continues to increase at substantial rates. Sales of electronic cigarettes have doubled every year since 2008, sales in 2013 are projected to reach $1.7 billion.46 This trend is of concern given the lack of regulation of these products. Until the FDA finalizes (and strengthens) its deeming rule for exerting its regulatory authority over electronic cigarettes, safety and health risks will increase as more people use these products. Safety issues arise from potentially defective battery powered heating elements, leaking spent nicotine cartridges,23 and nicotine poisoning in young children. Nicotine in electronic cigarettes may pose a greater poisoning risk than leaf tobacco.29 Electronic cigarette cartridges typically contain up to 20 mg of nicotine, while the estimated lethal dose of nicotine for a child as little as 10 mg.2 A recent study on unintentional nicotine poisonings among children under the age of six found a total of 13,705 product ingestions cases,47 while the National Poison Data System reports a 208% increase from 2012 to 2013 in liquid nicotine reported exposures to poison centers.48 Increased usage over the past three years suggests greater risk of poisoning and the need for safety and child-proofing regulations for these potentially lethal products. Finally, the proposed FDA deeming rule does not include restrictions on marketing of electronic cigarettes. This regulatory gap is alarming in light of recent research indicating that cigarette smokers were receptive to television ads and reported to intentions to use electronic cigarettes after viewing an ad that has been televised on numerous U.S. cable networks.49 This study has at least four limitations. First, our dual frame methodology is designed to reduce the potential for sample bias associated with either RDD or internet panel samples alone, but we still can’t eliminate the potential for noncoverage bias. Also, the use of the internet panel raises some concern about the representativeness of the sample. However, several studies demonstrate that this probability-based panel can produce results similar to well-designed RDD surveys50,51 and our use of this dual frame methodology produced estimates for current smoking that did not differ from those of several large, government surveys of U.S. adults.52 Second, these data are self-report and cross-sectional, and we could not verify that responses concerning cigarette smoking and electronic cigarette use were not biased. Studies comparing self-reported and biochemically assessed cigarette smoking, however, have supported the validity of self-reported cigarette smoking.53 To our knowledge, the validity of self-reported electronic cigarette use has not been assessed. Third, we did find evidence of a mode effect for awareness of electronic cigarettes in 2013. However, responses were consistent across modes in previous years and there were no differences in ever or current use in 2013. Fourth, the construct we used to examine the role e-cigarettes
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Mode Effects
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Funding The authors are supported by the American Academy of Pediatrics Julius B. Richmond Center of Excellence. Support for this article has been provided in part by Legacy (6033) and the Flight Attendant Medical Research Institute (052302). The information, views, and opinions contained herein are those of the authors and do not necessarily reflect the views and opinions of Legacy or the Flight Attendant Medical Research Institute.
Declaration of Interests None declared.
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may have had in the former smokers’ quit attempts is rather crude. Use by former smokers to quit smoking has different implications than use by former smokers who are reinitiating nicotine use (and possibly addiction). Although our data suggest that at least 40% of former smokers are reinitiating their tobacco use, a more refined construct would provide more confidence in this finding. In conclusion, there has been rapid growth in ever and current electronic cigarette use over the past four years, especially among young adults. Use is highest among young adults and current cigarette smokers. Although smokers are most likely to use these products, almost a third of current users are nonsmokers, suggesting that electronic cigarettes contribute to primary nicotine addiction and to renormalization of smoking behaviors. As Popova and Ling note,16 smoking rates decreased due to health concerns, regulatory and taxation burden, and the denormalization of smoking behaviors. Given the substantial growth in the use of electronic cigarettes, regulatory action is needed at the federal, state, and local levels to prevent the renormalization of tobacco use to ensure that these products do not contribute to preventable chronic disease.
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