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Risk factors for e-cigarette, conventional cigarette, and dual use in German adolescents: A cohort study
Preventive Medicine 74 (2015) 59–62
Contents lists available at ScienceDirect
Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Risk factors for e-cigarette, conventional cigarette, and dual use in German adolescents: A cohort study Reiner Hanewinkel a,b,⁎, Barbara Isensee a a b
Institute for Therapy and Health Research, IFT-Nord, Kiel, Germany University Medical Center, Kiel, Germany
a r t i c l e
i n f o
Available online 12 March 2015 Keywords: Adolescents E-cigarette Conventional cigarette Germany
a b s t r a c t Objective. Little is known about risk factors that are associated with e-cigarette use in adolescents. Methods. Multilevel mixed-effects regressions were performed to assess the relationship between factors that might be associated with e-cigarette, conventional cigarette and dual use in a cohort of 2693 German adolescents (mean age = 12.5 years; SD = 0.6). Risk factors were assessed in October 2010 and life time e-cigarette and conventional cigarette use were assessed 26 months later. Results. Use of e-cigarettes as well as use of conventional cigarette and dual use were associated with higher sensation seeking scores, and higher odds of having friends and parents who smoke conventional cigarettes, with conventional cigarette use additionally with male gender, being older, having higher odds of siblings who smoke conventional cigarettes, and less likely for adolescents who attend a Gymnasium, secondary school with a strong emphasis on academic learning. The use of conventional cigarettes at baseline did not predict e-cigarette use at follow-up. Lifetime prevalence of e-cigarette use was 4.7%, of conventional cigarette use 18.4%. A quarter of e-cigarette users (23.8%) never smoked a conventional cigarette. Discussion. Data indicate that e-cigarette and conventional cigarette use share many but not all risk factors. E-cigarettes could counteract the process of denormalization of smoking. © 2015 Elsevier Inc. All rights reserved.
Introduction Electronic cigarettes (e-cigarettes) are battery-powered nicotine delivery systems, which are marketed in many varieties (Hajek et al., 2014). Awareness and use of e-cigarettes have increased rapidly during the past few years (Pepper and Brewer, 2014). E-cigarettes expose users to high levels of particulates, which may increase cardiovascular risk. Since no tobacco is burnt, e-cigarettes reduce the exposure to cancerrelated agents. Therefore, it has been suggested that e-cigarettes are less harmful compared to conventional cigarettes. In addition, discussion of e-cigarettes has focused on their potential as a smoking cessation aid for adult smokers (Bullen et al., 2013). Little is known about e-cigarette use in young people. The prevalence of e-cigarette use in adolescents was recently summarized (Dutra and Glantz, 2014b). Ten cross-sectional studies with adolescent populations have been conducted in the United States, Poland, Korea, and France. The major finding is that e-cigarette use is increasing rapidly among youth in these countries. In Poland for example two crosssectional studies among 15- to 19-year olds found an absolute increase of ever e-cigarette use of about 45% points from 2010–11 to 2013–14 ⁎ Corresponding author at: Institute for Therapy and Health Research, IFT-Nord, Harmsstrasse 2, 24114 Kiel, Germany. Fax: +49 431 570 29 29. E-mail address: [email protected] (R. Hanewinkel).
http://dx.doi.org/10.1016/j.ypmed.2015.03.006 0091-7435/© 2015 Elsevier Inc. All rights reserved.
(Goniewicz et al., 2014; Goniewicz and Zielinska-Danch, 2012). A large scale cross-sectional study with US adolescents found that the use of e-cigarettes was associated with higher odds of ever or current cigarette smoking, and higher odds of established smoking (Dutra and Glantz, 2014a). A recently published cross-sectional paper on e-cigarette use among a large sample of Korean adolescents found that e-cigarette use was strongly associated with current and heavier cigarette smoking (Lee et al., 2014). The aim of our study is to contribute to the literature by investigating risk factors associated with e-cigarette and dual use in a sample of German adolescents and compare these risk factors with risk factors that are associated with conventional cigarette use. Method Design and sample We used data from a randomized-controlled school-based smoking prevention study described in detail elsewhere (Hansen et al., 2011; Isensee et al., 2014). A two-arm (intervention vs. control) prospective cluster randomized controlled trial with five waves was conducted in four federal states in Germany (Bremen, Hesse, North Rhine-Westphalia, Schleswig-Holstein). A total of 45 public secondary schools with 3444 students from 172 classes were recruited in September/October 2010 (baseline). In Germany, secondary schools include at least grades five to ten, and in some cases up to grade 13.
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R. Hanewinkel, B. Isensee / Preventive Medicine 74 (2015) 59–62
Factors that might be associated with e-cigarette and conventional cigarette use were assessed at baseline in fifth grade. Mean age of the baseline sample was 10.37 years (SD = 0.59) with 47.9% girls. E-cigarette and conventional cigarette use were assessed in seventh grade (December 2012). Data presented refer to the baseline and fourth wave survey. Out of 3444 students, it was possible to link follow-up data of 2693 students (retention rate = 78.2%) of whom 50.8% were male. The mean age at follow-up was 12.5 years (SD = 0.6) with a range of 11 to 15 years and 95.7% being 12 or 13 years old. Measures
Table 1 Lifetime use of conventional and e-cigarettes, assessed at follow-up in Germany, 2012. Use of conventional cigarettes (n)
No Yes Σ (%)
Use of e-cigarettes (n) No
Yes
Σ (%)
2135 393 2528 (95.3%)
30 96 126 (4.7%)
2165 (81.6%) 489 (18.4%) 2654 (100%)
Risk factor analyses
Risk factors were assessed at baseline. They were derived from studies that focused on risk factors of adolescent tobacco use. Sociodemographics include age, gender, type of school (Gymnasium vs. other type of school), migration background (mother and/or father were born outside Germany) and family affluence (Currie et al., 2008). As personal characteristic, sensation-seeking was assessed with three items (alpha = 0.73) (Sargent et al., 2010). Parent, sibling and peer conventional cigarette smoking were assessed as factors from social environment (no vs. any parent/sibling/peer smoking). Lifetime conventional cigarette smoking was assessed by asking how many cigarettes have ever been smoked in life. Nine answering categories (‘none’, ‘only a few puffs’, ‘1 cigarette’, ‘2 cigarettes’, ‘3–4 cigarettes’, ‘5–9 cigarettes’, ‘10–19 cigarettes’, ‘20–100 cigarettes’ and ‘N100 cigarettes’) were provided. Students having smoked at least a few puffs were considered as ever-smokers Outcome variables were assessed at follow-up: Lifetime conventional cigarette smoking was assessed the same way as it was at baseline. Lifetime use of e-cigarettes was assessed by asking “Have you ever used an electronic cigarette?” (yes/no). Students reporting both conventional and e-cigarette use were classified as dual users.
Results of the multilevel mixed effects logistic regressions are given in Table 2. The use of e-cigarettes as well as the use of conventional cigarette and dual use were associated with higher sensation seeking scores, and higher odds of having friends and parents who smoke conventional cigarettes. Conventional cigarettes use was also associated with male gender and being older, having higher odds of siblings who smoke conventional cigarettes, and less likely for adolescents who attend a Gymnasium. A total of 178 students (6.6%) reported lifetime use of conventional cigarettes at baseline. When including baseline smoking of conventional cigarettes as well into the regression models of e-cigarette and dual use (Table 3), it turned out that lifetime use of conventional cigarettes at baseline was neither associated with e-cigarette use at follow-up nor with dual use at follow-up.
Procedure
Sensitivity analyses were carried out with a subsample of the whole sample, the majority of 93.4% students, who never smoked a conventional cigarette at baseline (Table 4). Data indicate a high stability of the findings. Similar to the analyses of the whole sample we also found for this subsample, that the use of e-cigarettes as well as the use of conventional cigarettes and dual use were associated with higher sensation seeking scores, and higher odds of having friends who smoke conventional cigarettes. Conventional cigarettes use was also associated with being older, having higher odds of siblings who smoke conventional cigarettes, and less likely for adolescents who attend a Gymnasium. The only difference was that the association between gender and lifetime conventional cigarette smoking was only marginally significant and the association between parent smoking and lifetime dual use was insignificant in the analyses.
Data assessment was conducted by research staff in the class room. To permit a linking of individual baseline and follow-up data while assuring anonymity, students generated a seven-digit individual code (Galanti et al., 2007). At the end of the assessment, all questionnaires were placed in an envelope which was sealed in front of the class. Every student was assured that neither teachers nor parents were able to see the completed questionnaire. Analyses Predictors of attrition were examined by multilevel mixed effects logistic regressions. Descriptive statistics are crude values. To analyze the association between risk factors assessed at baseline and conventional, e-cigarette, and dual use assessed at follow-up multilevel mixed effects logistic regression models using Stata meqrlogit command were conducted. Because the data were clustered at school, and classroom level, random intercepts for all 2 levels were included in the models. Sensitivity analyses were carried out with students, who never smoked a conventional cigarette at baseline (93.4% of the baseline sample; N = 2515).
Results Attrition analysis More boys and more persons with migration background dropped out of the study. Persons lost to follow-up were significantly older at baseline, had lower family affluence scores, attended less often a Gymnasium, scored higher on sensation-seeking, and had more often friends/siblings/parents who smoked conventional cigarettes. Use of conventional and e-cigarettes A total of 2135 students (80.4%) never smoked a conventional nor an e-cigarette (Table 1). One hundred twenty six students (4.7%) had tried e-cigarettes, of whom 76.2% (n = 96) also tried conventional cigarettes (dual users). Nearly a quarter of e-cigarettes users (23.8%; n = 30) had never tried conventional cigarettes.
Sensitivity analyses
Discussion Almost 5% of a sample of 2693 German seventh graders had used e-cigarettes in 2012. E-cigarette use and dual use were associated with higher sensation seeking scores, and higher odds of having friends and parents who smoke conventional cigarettes. Lifetime prevalence of conventional cigarette use was 18.4%. Conventional cigarette use was associated with male gender, being older, higher sensation seeking scores, higher odds of friends/siblings/parents who smoke conventional cigarettes, and less likely in students attending a Gymnasium. Lifetime use of conventional cigarettes at baseline was neither associated with e-cigarette use at follow-up nor with dual use at follow-up. This study is subject to limitations inherent in any observational study. Loss to follow-up can affect generalizability, especially if there is selective attrition. However, the follow-up retention rate over the 26 month observation period was relatively high, cushioning the attrition effects. Another limitation is that we did not ask the students for e-cigarette use at baseline. Therefore, we are unable to analyze whether e-cigarette use predicts the onset of conventional cigarette use. But in 2010, e-cigarettes were promoted and offered in a very restricted extent in Germany generally, and for that time period we think that it is very unlikely that about 10 year old students had used e-cigarettes.
R. Hanewinkel, B. Isensee / Preventive Medicine 74 (2015) 59–62
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Table 2 Relationship between risk factors assessed 2010 and use of e-cigarettes, use of conventional cigarettes and dual use 26 months later in German adolescents. Results of three multilevel mixed effects logistic regressions with e-cigarette use, conventional cigarette use and dual use as outcomes. Risk factor at fifth grade
Substance use at seventh grade Lifetime e-cigarette use a
Girl Age Sensation seeking Migration background Family affluence Friend smoking (any) Sibling smoking (any) Parent smoking (any) Not at a Gymnasium a
Lifetime conventional cigarette use a
Lifetime dual use
Adjusted odds ratio
95% CI
Adjusted odds ratio
95% CI
Adjusteda odds ratio
95% CI
0.69 1.08 2.24 1.34 0.98 2.06 1.45 1.89 1.47
0.43–1.09 0.74–1.56 1.70–2.95 0.81–2.20 0.93–1.03 1.27–3.33 0.83–2.51 1.23–2.90 0.79–2.73
0.69 1.35 2.44 1.18 0.98 2.95 1.84 1.53 1.71
0.53–0.90 1.07–1.69 2.04–2.91 0.85–1.62 0.94–1.01 2.13–4.09 1.26–2.66 1.18–1.97 1.11–2.62
0.66 1.03 2.64 1.33 0.96 2.46 1.77 1.79 1.53
0.38–1.15 0.66–1.59 1.90–3.68 0.74–2.36 0.90–1.02 1.43–4.22 0.96–3.26 1.08–2.97 0.71–3.28
Adjusted for all variables in the table plus experimental condition.
Compared to ten international cross-sectional studies on the prevalence of e-cigarette use in adolescents, our German sample with a mean age of 12.5 years is the youngest one (Dutra and Glantz, 2014b). Prevalence of ever e-cigarette use varied in these studies between 0.5% among 13- to 18-year olds in 2008 in Korea to 62.1% in 15- to 10-year olds in Poland in 2013–14. A proportion of 4.7% seventh graders who had already experience with e-cigarettes in 2012 in Germany is an alarming number. We found that about a quarter of e-cigarette users never-smoked a conventional cigarette. This high number is in line with the ten other studies on e-cigarette use in young people, which report percentages between 7 and 32% of e-cigarette users without any experience of conventional cigarette use. In 2013 a cross-sectional school-based survey of a sample of 1941 high school students with a mean age of 14.6 years was conducted in Hawaii (Wills et al., 2015). The authors found a very large prevalence rate of e-cigarettes only use (17%), and that students who only used e-cigarettes were intermediate in levels of risk and protective factors between nonusers and dual users. We found a very similar risk pattern for e-cigarette and dual users in our longitudinal data set. Risk factors for smoking conventional cigarettes identified in the present study are in line with the literature: social factors and curiosity (sensation seeking) are as well associated with smoking as higher age and school type (Kuntz and Lampert, 2013; Tyas and Pederson, 1998). Gymnasiums are the most selective and most privileged secondary schools in Germany with a strong emphasis on academic learning. Within this environment as well as in early adolescence, conventional cigarette smoking occurs very seldom, i.e. smoking in younger adolescents and with higher educational status seems to be denormalized. Data from this study indicate that e-cigarette use and dual use were also associated with sensation seeking and smoking in the social environment, but not
with age and type of school. One might conclude that the e-cigarettes attract an even broader range of adolescents compared to conventional cigarettes: a certain proportion of adolescents experiment with e-cigarettes irrespective of age and educational status — both factors acting as “barriers of denormalization” for smoking conventional cigarettes. The finding that e-cigarettes and conventional cigarettes might share some, but not all risk factors is also supported by the fact that baseline smoking of conventional cigarettes was no predictor of e-cigarette use and dual use at follow-up in the multiple regression models. Nobel prize winner Eric Kandel discovered a molecular basis for nicotine as a gateway drug. He recently discussed the possibility that e-cigarette use in young people may function as a gateway to future drug use, especially cocaine use (Kandel and Kandel, 2014). Up to now, there are no data available to test this possibility, but it has been shown that the adolescent brain is very vulnerable to nicotine addiction (Lydon et al., 2014). Given the rapid growth of e-cigarette use in adolescents in many countries of the world, policies to protect youth from ecigarettes use should be implemented. The World Health Organization Framework Convention on Tobacco Control could be a blueprint for such policies. Funding This work was supported by German Cancer Aid (Grant Number: 108374). German Cancer Aid had no involvement in the study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. Participating investigators
Table 3 Relationship between lifetime use of conventional cigarettes assessed 2010 and use of ecigarettes and dual use 26 months later in German adolescents. Results of two multilevel mixed effects logistic regressions with e-cigarette use and dual use as outcomes. Risk factor at fifth grade
Substance use at seventh grade
Conflict of interest statement
Lifetime e-cigarette use Lifetime dual use
Ever smoked a conventional cigarette Girl Age Sensation seeking Migration background Family affluence Friend smoking (any) Sibling smoking (any) Parent smoking (any) Not at a Gymnasium a
Adjusteda odds ratio
95% CI
Adjusteda odds ratio
95% CI
1.50 0.70 1.06 2.21 1.31 0.98 1.83 1.39 1.80 1.48
0.78–2.84 0.44–1.11 0.73–1.54 1.67–2.92 0.80–2.16 0.92–1.03 1.19–2.83 0.79–2.43 1.14–2.85 0.80–2.73
1.16 0.67 1.02 2.64 1.32 0.96 2.37 1.76 1.62 1.55
0.55–2.43 0.38–1.17 0.66–1.58 1.89–3.68 0.74–2.36 0.90–1.02 1.33–4.20 1.05–2.92 0.94–2.77 0.72–3.31
Adjusted for all variables in the table plus experimental condition.
Karin Maruska, Julia Hansen and Marianne Bayrhuber contributed to the completion of the project by organizing the data assessments.
The authors declare that there are no conflicts of interests.
Ethics approval Ethics approval was provided by the Ethics Committee of the Medical Faculty of the University of Kiel (Ref.: D 419/10). Additional approvals (e.g., from ministries of education and parents) were sought as required. Trial registration Current controlled trials ISRCTN99442407.
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Table 4 Relationship between risk factors assessed 2010 and use of e-cigarettes and conventional cigarettes and dual use 26 months later in German adolescents, who never smoked a conventional cigarette at baseline (n = 2515; 93.0% of the baseline sample). Results of three multilevel mixed effects logistic regressions with e-cigarette use, conventional cigarette use and dual use as outcomes. Risk factor at fifth grade
Substance use at seventh grade Lifetime e-cigarette use
Girl Age Sensation seeking Migration background Family affluence Friend smoking (any) Sibling smoking (any) Parent smoking (any) Not at a Gymnasium a
Lifetime conventional cigarette use
Lifetime dual use
Adjustedaodds ratio
95% CI
Adjusteda odds ratio
95% CI
Adjusteda odds ratio
95% CI
0.69 1.11 2.14 1.52 0.98 1.78 1.45 1.80 1.62
0.43–1.12 0.74–1.66 1.60–2.87 0.90–2.54 0.93–1.04 1.02–3.13 0.78–2.71 1.14–2.85 0.93–2.81
0.76 1.30 2.35 1.18 0.98 2.34 1.73 1.52 1.66
0.57–1.00 1.02–1.66 1.95–2.83 0.84–1.67 0.94–1.01 1.64–3.44 1.15–2.60 1.16–2.00 1.06–2.60
0.70 1.07 2.58 1.57 0.96 2.37 1.85 1.62 1.65
0.39–1.25 0.66–1.73 1.81–3.68 0.86–2.88 0.89–1.02 1.27–4.39 0.93–3.67 0.94–2.77 0.81–3.33
Adjusted for all variables in the table plus experimental condition.
Acknowledgments Malin Bachmann, Tina Basner, Jana Blumkowski, Dorothea Breckwoldt, Roxana Buzila, Svenja Cleve, Malte Dincher, Eva-Maria Eggers, Nadia El Bouhayati, Almut Engelhardt, Sigrid Feierabend, Sarah Göhlert, Lars Grabbe, Judith Hanewinkel, Oksana Herdt, Semiha Idrizovic, Sabiha Izaamriouane, Martin Karsten, Andre Lischick, Stefanie Otte, Serdar Peker, Ines Pohlmann, Wiebke Pustal, Gesa Sander, Christoph Schlüter, Björn Seiler, Beate Steiber, Alexander Wierzock and Nicole Wilmes assessed the data. The authors would like to thank their partners: Institut für Qualitätsentwicklung an Schulen SchleswigHolstein, Landesinstitut für Schule Bremen, Krisenhilfe Bochum, Fachstelle für Suchtprävention im Wetteraukreis, Fachstelle für Suchtprävention des Zweckverbandes der Diakonie Bad Hersfeld, Diakonie Herford, Koordinationsstelle Schulische Suchtvorbeugung, Fachstelle für Suchtvorbeugung Dortmund, Hessische Landesstelle für Suchtfragen, Ginko Stiftung für Prävention and all schools that participated in the study. References Bullen, C., Howe, C., Laugesen, M., McRobbie, H., Parag, V., Williman, J., Walker, N., 2013. Electronic cigarettes for smoking cessation: a randomised controlled trial. Lancet 382, 1629–1637. Currie, C., Molcho, M., Boyce, W., Holstein, B., Torsheim, T., Richter, M., 2008. Researching health inequalities in adolescents: the development of the Health Behaviour in School-Aged Children (HBSC) family affluence scale. Soc. Sci. Med. 66, 1429–1436. Dutra, L.M., Glantz, S.A., 2014a. Electronic cigarettes and conventional cigarette use among U.S. adolescents: a cross-sectional study. JAMA Pediatr. 168, 610–617. Dutra, L.M., Glantz, S.A., 2014b. High international electronic cigarette use among never smoker adolescents. J. Adolesc. Health 55, 595–597.
Galanti, M.R., Siliquini, R., Cuomo, L., Melero, J.C., Panella, M., Faggiano, F., 2007. Testing anonymous link procedures for follow-up of adolescents in a school-based trial: the EU-DAP pilot study. Prev. Med. 44, 174–177. Goniewicz, M.L., Zielinska-Danch, W., 2012. Electronic cigarette use among teenagers and young adults in Poland. Pediatrics 130, e879–e885. Goniewicz, M.L., Gawron, M., Nadolska, J., Balwicki, L., Sobczak, A., 2014. Rise in electronic cigarette use among adolescents in Poland. J. Adolesc. Health 55, 713–715. Hajek, P., Etter, J.F., Benowitz, N., Eissenberg, T., McRobbie, H., 2014. Electronic cigarettes: review of use, content, safety, effects on smokers and potential for harm and benefit. Addiction 109, 1801–1810. Hansen, J., Hanewinkel, R., Maruska, K., Isensee, B., 2011. The ‘Eigenständig werden’ prevention trial: a cluster randomised controlled study on a school-based life skills programme to prevent substance use onset. BMJ Open 1, e000352. Isensee, B., Hansen, J., Maruska, K., Hanewinkel, R., 2014. Effects of a school-based prevention programme on smoking in early adolescence: a 6-month follow-up of the ‘Eigenständig werden’ cluster randomised trial. BMJ Open 4, e004422. Kandel, E.R., Kandel, D.B., 2014. Shattuck lecture. A molecular basis for nicotine as a gateway drug. N. Engl. J. Med. 371, 932–943. Kuntz, B., Lampert, T., 2013. Educational differences in smoking among adolescents in Germany: what is the role of parental and adolescent education levels and intergenerational educational mobility? Int. J. Environ. Res. Public Health 10, 3015–3032. Lee, S., Grana, R.A., Glantz, S.A., 2014. Electronic cigarette use among Korean adolescents: a cross-sectional study of market penetration, dual use, and relationship to quit attempts and former smoking. J. Adolesc. Health 54, 684–690. Lydon, D.M., Wilson, S.J., Child, A., Geier, C.F., 2014. Adolescent brain maturation and smoking: what we know and where we're headed. Neurosci. Biobehav. Rev. 45, 323–342. Pepper, J.K., Brewer, N.T., 2014. Electronic nicotine delivery system (electronic cigarette) awareness, use, reactions and beliefs: a systematic review. Tob. Control. 23, 375–384. Sargent, J.D., Tanski, S., Stoolmiller, M., Hanewinkel, R., 2010. Using sensation seeking to target adolescents for substance use interventions. Addiction 105, 506–514. Tyas, S.L., Pederson, L.L., 1998. Psychosocial factors related to adolescent smoking: a critical review of the literature. Tob. Control. 7, 409–420. Wills, T.A., Knight, R., Williams, R.J., Pagano, I., Sargent, J.D., 2015. Risk factors for exclusive e-cigarette use and dual e-cigarette use and tobacco use in adolescents. Pediatrics 135, e43–e51.
Contents lists available at ScienceDirect
Preventive Medicine journal homepage: www.elsevier.com/locate/ypmed
Risk factors for e-cigarette, conventional cigarette, and dual use in German adolescents: A cohort study Reiner Hanewinkel a,b,⁎, Barbara Isensee a a b
Institute for Therapy and Health Research, IFT-Nord, Kiel, Germany University Medical Center, Kiel, Germany
a r t i c l e
i n f o
Available online 12 March 2015 Keywords: Adolescents E-cigarette Conventional cigarette Germany
a b s t r a c t Objective. Little is known about risk factors that are associated with e-cigarette use in adolescents. Methods. Multilevel mixed-effects regressions were performed to assess the relationship between factors that might be associated with e-cigarette, conventional cigarette and dual use in a cohort of 2693 German adolescents (mean age = 12.5 years; SD = 0.6). Risk factors were assessed in October 2010 and life time e-cigarette and conventional cigarette use were assessed 26 months later. Results. Use of e-cigarettes as well as use of conventional cigarette and dual use were associated with higher sensation seeking scores, and higher odds of having friends and parents who smoke conventional cigarettes, with conventional cigarette use additionally with male gender, being older, having higher odds of siblings who smoke conventional cigarettes, and less likely for adolescents who attend a Gymnasium, secondary school with a strong emphasis on academic learning. The use of conventional cigarettes at baseline did not predict e-cigarette use at follow-up. Lifetime prevalence of e-cigarette use was 4.7%, of conventional cigarette use 18.4%. A quarter of e-cigarette users (23.8%) never smoked a conventional cigarette. Discussion. Data indicate that e-cigarette and conventional cigarette use share many but not all risk factors. E-cigarettes could counteract the process of denormalization of smoking. © 2015 Elsevier Inc. All rights reserved.
Introduction Electronic cigarettes (e-cigarettes) are battery-powered nicotine delivery systems, which are marketed in many varieties (Hajek et al., 2014). Awareness and use of e-cigarettes have increased rapidly during the past few years (Pepper and Brewer, 2014). E-cigarettes expose users to high levels of particulates, which may increase cardiovascular risk. Since no tobacco is burnt, e-cigarettes reduce the exposure to cancerrelated agents. Therefore, it has been suggested that e-cigarettes are less harmful compared to conventional cigarettes. In addition, discussion of e-cigarettes has focused on their potential as a smoking cessation aid for adult smokers (Bullen et al., 2013). Little is known about e-cigarette use in young people. The prevalence of e-cigarette use in adolescents was recently summarized (Dutra and Glantz, 2014b). Ten cross-sectional studies with adolescent populations have been conducted in the United States, Poland, Korea, and France. The major finding is that e-cigarette use is increasing rapidly among youth in these countries. In Poland for example two crosssectional studies among 15- to 19-year olds found an absolute increase of ever e-cigarette use of about 45% points from 2010–11 to 2013–14 ⁎ Corresponding author at: Institute for Therapy and Health Research, IFT-Nord, Harmsstrasse 2, 24114 Kiel, Germany. Fax: +49 431 570 29 29. E-mail address: [email protected] (R. Hanewinkel).
http://dx.doi.org/10.1016/j.ypmed.2015.03.006 0091-7435/© 2015 Elsevier Inc. All rights reserved.
(Goniewicz et al., 2014; Goniewicz and Zielinska-Danch, 2012). A large scale cross-sectional study with US adolescents found that the use of e-cigarettes was associated with higher odds of ever or current cigarette smoking, and higher odds of established smoking (Dutra and Glantz, 2014a). A recently published cross-sectional paper on e-cigarette use among a large sample of Korean adolescents found that e-cigarette use was strongly associated with current and heavier cigarette smoking (Lee et al., 2014). The aim of our study is to contribute to the literature by investigating risk factors associated with e-cigarette and dual use in a sample of German adolescents and compare these risk factors with risk factors that are associated with conventional cigarette use. Method Design and sample We used data from a randomized-controlled school-based smoking prevention study described in detail elsewhere (Hansen et al., 2011; Isensee et al., 2014). A two-arm (intervention vs. control) prospective cluster randomized controlled trial with five waves was conducted in four federal states in Germany (Bremen, Hesse, North Rhine-Westphalia, Schleswig-Holstein). A total of 45 public secondary schools with 3444 students from 172 classes were recruited in September/October 2010 (baseline). In Germany, secondary schools include at least grades five to ten, and in some cases up to grade 13.
60
R. Hanewinkel, B. Isensee / Preventive Medicine 74 (2015) 59–62
Factors that might be associated with e-cigarette and conventional cigarette use were assessed at baseline in fifth grade. Mean age of the baseline sample was 10.37 years (SD = 0.59) with 47.9% girls. E-cigarette and conventional cigarette use were assessed in seventh grade (December 2012). Data presented refer to the baseline and fourth wave survey. Out of 3444 students, it was possible to link follow-up data of 2693 students (retention rate = 78.2%) of whom 50.8% were male. The mean age at follow-up was 12.5 years (SD = 0.6) with a range of 11 to 15 years and 95.7% being 12 or 13 years old. Measures
Table 1 Lifetime use of conventional and e-cigarettes, assessed at follow-up in Germany, 2012. Use of conventional cigarettes (n)
No Yes Σ (%)
Use of e-cigarettes (n) No
Yes
Σ (%)
2135 393 2528 (95.3%)
30 96 126 (4.7%)
2165 (81.6%) 489 (18.4%) 2654 (100%)
Risk factor analyses
Risk factors were assessed at baseline. They were derived from studies that focused on risk factors of adolescent tobacco use. Sociodemographics include age, gender, type of school (Gymnasium vs. other type of school), migration background (mother and/or father were born outside Germany) and family affluence (Currie et al., 2008). As personal characteristic, sensation-seeking was assessed with three items (alpha = 0.73) (Sargent et al., 2010). Parent, sibling and peer conventional cigarette smoking were assessed as factors from social environment (no vs. any parent/sibling/peer smoking). Lifetime conventional cigarette smoking was assessed by asking how many cigarettes have ever been smoked in life. Nine answering categories (‘none’, ‘only a few puffs’, ‘1 cigarette’, ‘2 cigarettes’, ‘3–4 cigarettes’, ‘5–9 cigarettes’, ‘10–19 cigarettes’, ‘20–100 cigarettes’ and ‘N100 cigarettes’) were provided. Students having smoked at least a few puffs were considered as ever-smokers Outcome variables were assessed at follow-up: Lifetime conventional cigarette smoking was assessed the same way as it was at baseline. Lifetime use of e-cigarettes was assessed by asking “Have you ever used an electronic cigarette?” (yes/no). Students reporting both conventional and e-cigarette use were classified as dual users.
Results of the multilevel mixed effects logistic regressions are given in Table 2. The use of e-cigarettes as well as the use of conventional cigarette and dual use were associated with higher sensation seeking scores, and higher odds of having friends and parents who smoke conventional cigarettes. Conventional cigarettes use was also associated with male gender and being older, having higher odds of siblings who smoke conventional cigarettes, and less likely for adolescents who attend a Gymnasium. A total of 178 students (6.6%) reported lifetime use of conventional cigarettes at baseline. When including baseline smoking of conventional cigarettes as well into the regression models of e-cigarette and dual use (Table 3), it turned out that lifetime use of conventional cigarettes at baseline was neither associated with e-cigarette use at follow-up nor with dual use at follow-up.
Procedure
Sensitivity analyses were carried out with a subsample of the whole sample, the majority of 93.4% students, who never smoked a conventional cigarette at baseline (Table 4). Data indicate a high stability of the findings. Similar to the analyses of the whole sample we also found for this subsample, that the use of e-cigarettes as well as the use of conventional cigarettes and dual use were associated with higher sensation seeking scores, and higher odds of having friends who smoke conventional cigarettes. Conventional cigarettes use was also associated with being older, having higher odds of siblings who smoke conventional cigarettes, and less likely for adolescents who attend a Gymnasium. The only difference was that the association between gender and lifetime conventional cigarette smoking was only marginally significant and the association between parent smoking and lifetime dual use was insignificant in the analyses.
Data assessment was conducted by research staff in the class room. To permit a linking of individual baseline and follow-up data while assuring anonymity, students generated a seven-digit individual code (Galanti et al., 2007). At the end of the assessment, all questionnaires were placed in an envelope which was sealed in front of the class. Every student was assured that neither teachers nor parents were able to see the completed questionnaire. Analyses Predictors of attrition were examined by multilevel mixed effects logistic regressions. Descriptive statistics are crude values. To analyze the association between risk factors assessed at baseline and conventional, e-cigarette, and dual use assessed at follow-up multilevel mixed effects logistic regression models using Stata meqrlogit command were conducted. Because the data were clustered at school, and classroom level, random intercepts for all 2 levels were included in the models. Sensitivity analyses were carried out with students, who never smoked a conventional cigarette at baseline (93.4% of the baseline sample; N = 2515).
Results Attrition analysis More boys and more persons with migration background dropped out of the study. Persons lost to follow-up were significantly older at baseline, had lower family affluence scores, attended less often a Gymnasium, scored higher on sensation-seeking, and had more often friends/siblings/parents who smoked conventional cigarettes. Use of conventional and e-cigarettes A total of 2135 students (80.4%) never smoked a conventional nor an e-cigarette (Table 1). One hundred twenty six students (4.7%) had tried e-cigarettes, of whom 76.2% (n = 96) also tried conventional cigarettes (dual users). Nearly a quarter of e-cigarettes users (23.8%; n = 30) had never tried conventional cigarettes.
Sensitivity analyses
Discussion Almost 5% of a sample of 2693 German seventh graders had used e-cigarettes in 2012. E-cigarette use and dual use were associated with higher sensation seeking scores, and higher odds of having friends and parents who smoke conventional cigarettes. Lifetime prevalence of conventional cigarette use was 18.4%. Conventional cigarette use was associated with male gender, being older, higher sensation seeking scores, higher odds of friends/siblings/parents who smoke conventional cigarettes, and less likely in students attending a Gymnasium. Lifetime use of conventional cigarettes at baseline was neither associated with e-cigarette use at follow-up nor with dual use at follow-up. This study is subject to limitations inherent in any observational study. Loss to follow-up can affect generalizability, especially if there is selective attrition. However, the follow-up retention rate over the 26 month observation period was relatively high, cushioning the attrition effects. Another limitation is that we did not ask the students for e-cigarette use at baseline. Therefore, we are unable to analyze whether e-cigarette use predicts the onset of conventional cigarette use. But in 2010, e-cigarettes were promoted and offered in a very restricted extent in Germany generally, and for that time period we think that it is very unlikely that about 10 year old students had used e-cigarettes.
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Table 2 Relationship between risk factors assessed 2010 and use of e-cigarettes, use of conventional cigarettes and dual use 26 months later in German adolescents. Results of three multilevel mixed effects logistic regressions with e-cigarette use, conventional cigarette use and dual use as outcomes. Risk factor at fifth grade
Substance use at seventh grade Lifetime e-cigarette use a
Girl Age Sensation seeking Migration background Family affluence Friend smoking (any) Sibling smoking (any) Parent smoking (any) Not at a Gymnasium a
Lifetime conventional cigarette use a
Lifetime dual use
Adjusted odds ratio
95% CI
Adjusted odds ratio
95% CI
Adjusteda odds ratio
95% CI
0.69 1.08 2.24 1.34 0.98 2.06 1.45 1.89 1.47
0.43–1.09 0.74–1.56 1.70–2.95 0.81–2.20 0.93–1.03 1.27–3.33 0.83–2.51 1.23–2.90 0.79–2.73
0.69 1.35 2.44 1.18 0.98 2.95 1.84 1.53 1.71
0.53–0.90 1.07–1.69 2.04–2.91 0.85–1.62 0.94–1.01 2.13–4.09 1.26–2.66 1.18–1.97 1.11–2.62
0.66 1.03 2.64 1.33 0.96 2.46 1.77 1.79 1.53
0.38–1.15 0.66–1.59 1.90–3.68 0.74–2.36 0.90–1.02 1.43–4.22 0.96–3.26 1.08–2.97 0.71–3.28
Adjusted for all variables in the table plus experimental condition.
Compared to ten international cross-sectional studies on the prevalence of e-cigarette use in adolescents, our German sample with a mean age of 12.5 years is the youngest one (Dutra and Glantz, 2014b). Prevalence of ever e-cigarette use varied in these studies between 0.5% among 13- to 18-year olds in 2008 in Korea to 62.1% in 15- to 10-year olds in Poland in 2013–14. A proportion of 4.7% seventh graders who had already experience with e-cigarettes in 2012 in Germany is an alarming number. We found that about a quarter of e-cigarette users never-smoked a conventional cigarette. This high number is in line with the ten other studies on e-cigarette use in young people, which report percentages between 7 and 32% of e-cigarette users without any experience of conventional cigarette use. In 2013 a cross-sectional school-based survey of a sample of 1941 high school students with a mean age of 14.6 years was conducted in Hawaii (Wills et al., 2015). The authors found a very large prevalence rate of e-cigarettes only use (17%), and that students who only used e-cigarettes were intermediate in levels of risk and protective factors between nonusers and dual users. We found a very similar risk pattern for e-cigarette and dual users in our longitudinal data set. Risk factors for smoking conventional cigarettes identified in the present study are in line with the literature: social factors and curiosity (sensation seeking) are as well associated with smoking as higher age and school type (Kuntz and Lampert, 2013; Tyas and Pederson, 1998). Gymnasiums are the most selective and most privileged secondary schools in Germany with a strong emphasis on academic learning. Within this environment as well as in early adolescence, conventional cigarette smoking occurs very seldom, i.e. smoking in younger adolescents and with higher educational status seems to be denormalized. Data from this study indicate that e-cigarette use and dual use were also associated with sensation seeking and smoking in the social environment, but not
with age and type of school. One might conclude that the e-cigarettes attract an even broader range of adolescents compared to conventional cigarettes: a certain proportion of adolescents experiment with e-cigarettes irrespective of age and educational status — both factors acting as “barriers of denormalization” for smoking conventional cigarettes. The finding that e-cigarettes and conventional cigarettes might share some, but not all risk factors is also supported by the fact that baseline smoking of conventional cigarettes was no predictor of e-cigarette use and dual use at follow-up in the multiple regression models. Nobel prize winner Eric Kandel discovered a molecular basis for nicotine as a gateway drug. He recently discussed the possibility that e-cigarette use in young people may function as a gateway to future drug use, especially cocaine use (Kandel and Kandel, 2014). Up to now, there are no data available to test this possibility, but it has been shown that the adolescent brain is very vulnerable to nicotine addiction (Lydon et al., 2014). Given the rapid growth of e-cigarette use in adolescents in many countries of the world, policies to protect youth from ecigarettes use should be implemented. The World Health Organization Framework Convention on Tobacco Control could be a blueprint for such policies. Funding This work was supported by German Cancer Aid (Grant Number: 108374). German Cancer Aid had no involvement in the study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. Participating investigators
Table 3 Relationship between lifetime use of conventional cigarettes assessed 2010 and use of ecigarettes and dual use 26 months later in German adolescents. Results of two multilevel mixed effects logistic regressions with e-cigarette use and dual use as outcomes. Risk factor at fifth grade
Substance use at seventh grade
Conflict of interest statement
Lifetime e-cigarette use Lifetime dual use
Ever smoked a conventional cigarette Girl Age Sensation seeking Migration background Family affluence Friend smoking (any) Sibling smoking (any) Parent smoking (any) Not at a Gymnasium a
Adjusteda odds ratio
95% CI
Adjusteda odds ratio
95% CI
1.50 0.70 1.06 2.21 1.31 0.98 1.83 1.39 1.80 1.48
0.78–2.84 0.44–1.11 0.73–1.54 1.67–2.92 0.80–2.16 0.92–1.03 1.19–2.83 0.79–2.43 1.14–2.85 0.80–2.73
1.16 0.67 1.02 2.64 1.32 0.96 2.37 1.76 1.62 1.55
0.55–2.43 0.38–1.17 0.66–1.58 1.89–3.68 0.74–2.36 0.90–1.02 1.33–4.20 1.05–2.92 0.94–2.77 0.72–3.31
Adjusted for all variables in the table plus experimental condition.
Karin Maruska, Julia Hansen and Marianne Bayrhuber contributed to the completion of the project by organizing the data assessments.
The authors declare that there are no conflicts of interests.
Ethics approval Ethics approval was provided by the Ethics Committee of the Medical Faculty of the University of Kiel (Ref.: D 419/10). Additional approvals (e.g., from ministries of education and parents) were sought as required. Trial registration Current controlled trials ISRCTN99442407.
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R. Hanewinkel, B. Isensee / Preventive Medicine 74 (2015) 59–62
Table 4 Relationship between risk factors assessed 2010 and use of e-cigarettes and conventional cigarettes and dual use 26 months later in German adolescents, who never smoked a conventional cigarette at baseline (n = 2515; 93.0% of the baseline sample). Results of three multilevel mixed effects logistic regressions with e-cigarette use, conventional cigarette use and dual use as outcomes. Risk factor at fifth grade
Substance use at seventh grade Lifetime e-cigarette use
Girl Age Sensation seeking Migration background Family affluence Friend smoking (any) Sibling smoking (any) Parent smoking (any) Not at a Gymnasium a
Lifetime conventional cigarette use
Lifetime dual use
Adjustedaodds ratio
95% CI
Adjusteda odds ratio
95% CI
Adjusteda odds ratio
95% CI
0.69 1.11 2.14 1.52 0.98 1.78 1.45 1.80 1.62
0.43–1.12 0.74–1.66 1.60–2.87 0.90–2.54 0.93–1.04 1.02–3.13 0.78–2.71 1.14–2.85 0.93–2.81
0.76 1.30 2.35 1.18 0.98 2.34 1.73 1.52 1.66
0.57–1.00 1.02–1.66 1.95–2.83 0.84–1.67 0.94–1.01 1.64–3.44 1.15–2.60 1.16–2.00 1.06–2.60
0.70 1.07 2.58 1.57 0.96 2.37 1.85 1.62 1.65
0.39–1.25 0.66–1.73 1.81–3.68 0.86–2.88 0.89–1.02 1.27–4.39 0.93–3.67 0.94–2.77 0.81–3.33
Adjusted for all variables in the table plus experimental condition.
Acknowledgments Malin Bachmann, Tina Basner, Jana Blumkowski, Dorothea Breckwoldt, Roxana Buzila, Svenja Cleve, Malte Dincher, Eva-Maria Eggers, Nadia El Bouhayati, Almut Engelhardt, Sigrid Feierabend, Sarah Göhlert, Lars Grabbe, Judith Hanewinkel, Oksana Herdt, Semiha Idrizovic, Sabiha Izaamriouane, Martin Karsten, Andre Lischick, Stefanie Otte, Serdar Peker, Ines Pohlmann, Wiebke Pustal, Gesa Sander, Christoph Schlüter, Björn Seiler, Beate Steiber, Alexander Wierzock and Nicole Wilmes assessed the data. The authors would like to thank their partners: Institut für Qualitätsentwicklung an Schulen SchleswigHolstein, Landesinstitut für Schule Bremen, Krisenhilfe Bochum, Fachstelle für Suchtprävention im Wetteraukreis, Fachstelle für Suchtprävention des Zweckverbandes der Diakonie Bad Hersfeld, Diakonie Herford, Koordinationsstelle Schulische Suchtvorbeugung, Fachstelle für Suchtvorbeugung Dortmund, Hessische Landesstelle für Suchtfragen, Ginko Stiftung für Prävention and all schools that participated in the study. References Bullen, C., Howe, C., Laugesen, M., McRobbie, H., Parag, V., Williman, J., Walker, N., 2013. Electronic cigarettes for smoking cessation: a randomised controlled trial. Lancet 382, 1629–1637. Currie, C., Molcho, M., Boyce, W., Holstein, B., Torsheim, T., Richter, M., 2008. Researching health inequalities in adolescents: the development of the Health Behaviour in School-Aged Children (HBSC) family affluence scale. Soc. Sci. Med. 66, 1429–1436. Dutra, L.M., Glantz, S.A., 2014a. Electronic cigarettes and conventional cigarette use among U.S. adolescents: a cross-sectional study. JAMA Pediatr. 168, 610–617. Dutra, L.M., Glantz, S.A., 2014b. High international electronic cigarette use among never smoker adolescents. J. Adolesc. Health 55, 595–597.
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