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Int. J. Environ. Res. Public Health 2019, 16, 4661; doi:10.3390/ijerph16234661 www.mdpi.com/journal/ijerph
Article
E-Liquid Flavor Preferences and Individual Factors
Related to Vaping: A Survey among Dutch Never-Users,
Smokers, Dual Users, and Exclusive Vapers
Kim AGJ Romijnders 1,2,*, Erna JZ Krüsemann 1,3, Sanne Boesveldt 3, Kees de Graaf 3, Hein de Vries 2
and Reinskje Talhout 1
1 Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Antonie van
Leeuwenhoeklaan 9, 3721 MA Bilthoven, The Netherlands; erna.krusemann@rivm.nl (E.J.Z.K.);
reinskje.talhout@rivm.nl (R.T.)
2 Department of Health Promotion, School for Public Health and Primary Care (CAPHRI), Maastricht University,
Universiteitssingel 40, 6229 ER Maastricht, The Netherlands; hein.devries@maastrichtuniversity.nl (H.d.V.)
3 Division of Human Nutrition and Health, Wageningen University, Stippeneng 4,
6708 WE Wageningen, The Netherlands; sanne.boesveldt@wur.nl (S.B.); kees.degraaf@wur.nl (K.d.G.)
* Correspondence: kim.romijnders@rivm.nl; Tel.: +31-30-274-4512
Received: 18 September 2019; Accepted: 20 November 2019; Published: 22 November 2019
Abstract: Appealing product characteristics, such as flavors, may stimulate e-cigarette use. While
switching to e-cigarettes may reduce harm for smokers, concerns exist about e-cigarette use among never-
smokers. The role of flavors in the decision to switch to or refrain from vaping is unclear. This study used
a bottom–up approach to investigate the relation between flavor preferences and individual factors related
to vaping between various user groups. A cross-sectional survey was conducted among never-users (n =
407), smokers (n = 138), dual users (n = 122), and exclusive vapers (n = 61) in the Netherlands.
Demographics, attractiveness of product characteristics, flavor preferences, and individual factors related
to vaping (knowledge, trust, perceived susceptibility, attitude, social influence, deliberation, and
intention) were assessed. The availability of different flavors was the most attractive characteristic of e-
cigarettes. Dual users and exclusive vapers had most often used tobacco and menthol/mint flavors when
they first started vaping. Compared to dual users, exclusive vapers currently used more fruit and sweet
flavors. Never-users who were interested in trying an e-liquid flavor had more knowledge about and a
more positive attitude towards e-cigarettes. Smokers who were interested in trying a flavor had a more
positive attitude towards e-cigarettes and experienced the social influence towards not using e-cigarettes
as less strong than those who did not want to try any flavor. Hence, individual factors related to vaping
differed depending on whether never-users and smokers wanted to try an e-liquid flavor. This means that
flavors may moderate differences found in individual factors related to vaping, or vice versa.
Keywords: electronic cigarettes; flavors; preference; smoking; vaping; knowledge; attitude; deliberation;
perceived susceptibility
1. Introduction
Although vaping prevalence in the Netherlands is currently rather low (3%) [1], the use of electronic
cigarettes (e-cigarettes) increased worldwide in recent years [2,3]. The majority of e-cigarette users are
former or current smokers [4–6] and literature has showed that e-cigarette use (i.e., vaping) may be
associated with smoking cessation and reduction [7,8]. In the Netherlands, e-cigarettes are more often used
by daily smokers (12%) compared to non-daily smokers (4%). Worldwide, vaping is also becoming
Int. J. Environ. Res. Public Health 2019, 16, 4661 2 of 15
increasingly popular among adolescent non- and never-smokers [3,9,10]. The regulation of e-cigarettes in
order to optimize public health benefits is challenging and is currently an important topic of debate.
Compared to cigarette smoking, vaping may reduce harm among smokers [11–14], but literature showed
that e-cigarettes contain toxic ingredients [11]. In addition, concerns have been raised that vaping may
contribute to nicotine addiction and the renormalization of cigarette smoking in adolescent never-smokers
[3,15–18]. Consequently, from a public health perspective, the initiation of vaping by current non- and
never-smokers and, thereby, exposure to potentially toxic ingredients should be prevented [18].
Research is needed to better understand differences between the initiation of e-cigarette use by current
smokers versus non-smokers in order to inform regulators about policy making regarding e-cigarettes in
order to develop targeted health communication for smokers, non-smokers, and e-cigarette users. Previous
studies found differences in individual factors related to e-cigarettes among never-users, smokers, dual
users, and e-cigarette users [19]. Individual factors that were found to differ included, for example,
knowledge, perceived susceptibility, severity, trust, attitudes, deliberation, social influence, and intention
[19–23]. Furthermore, literature showed that the importance of product characteristics such as design, price,
and flavors may differ between adult smokers and adolescent non-smokers [24–27]. However, the relation
between e-cigarette product characteristics and individual-level factors has been neglected.
A recent study hypothesized that there is an important interplay between individual-level factors and
the characteristics of tobacco products [28]. Since product characteristics (e.g., flavors, design, and price)
influence e-cigarette appeal [24–27] and may influence a person’s attitude towards e-cigarettes [24,28], such
an interplay may also exist for e-cigarettes. However, thus far, most studies on e-cigarettes focused either
on product characteristics [29], or on socio-cognitive factors related to vaping behavior [30]. In contrast,
researchers in the food and nutrition domain have already recognized the importance of the interaction
between product characteristics and individual-level decision-making factors in food choice [31–33]. For
example, a model by Shepherd [31] shows that food choice is influenced by the interaction between physical
or chemical properties of food, such as flavors (product factor), and the individual’s perception of and
attitude towards those sensory properties (individual-level factors). Furthermore, flavors and other sensory
properties are recognized as by far the most important factors in the acceptance and rejection of food
products [32].
Similarly, since e-liquid flavors are recognized as an important reason for e-cigarette use [24], flavors
may interact with individual-level factors related to vaping. Moreover, the availability of many different,
mostly sweet, e-liquid flavors is an important reason for vaping among different types of users [24,29].
Research showed that for most e-cigarette users, and in particular for youth, the first and current e-liquid
had a flavor other than tobacco [26,34,35]. In addition, flavors increase the probability of choosing e-
cigarettes in an online discrete choice experiment among youth, for both never-users and ever-users of e-
cigarettes [36]. Therefore, besides investigating product characteristics as reasons for e-cigarette use,
additional research is needed to investigate the interaction between flavors as an e-cigarette product
characteristic and individual factors related to vaping.
To increase our understanding of differences in e-cigarette appeal between user groups, this study
firstly investigates which product characteristics are found attractive by Dutch never-users, smokers, dual
users, and exclusive vapers. Secondly, we aim to determine the flavor preferences of Dutch never-users,
smokers, dual users, and exclusive vapers. Thirdly, we aim to explore whether eight individual factors
related to vaping differ between never-users and smokers who reported to be interested in trying an e-
liquid flavor compared to those who reported not to be interested in trying any e-liquid flavor.
2. Materials and Methods
A cross-sectional survey was conducted in the Netherlands among never-users of e-cigarettes and
cigarettes, cigarette smokers, dual users of e-cigarettes and cigarettes, and e-cigarette users. The survey was
administered in May 2017 through the online survey panel Flycatcher, which is an ISO-certified
independent research panel specialized in online research [37]. The study was approved by the Medical
Int. J. Environ. Res. Public Health 2019, 16, 4661 3 of 15
Ethics Committee of Zuyderland – Zuyd (17-N-88). The recruitment, participant characteristics, and survey
were previously described in Romijnders, et al. [38].
2.1. Recruitment and Participant Characteristics
In total, 12,750 invitations were sent to panelists who met the following inclusion criteria: being able to
understand Dutch; being aware of e-cigarettes; aged 13–17 years (adolescents) or 18 years and older (adults).
Sample size was determined based on a power of 80% to identify a minimal difference of 1 on a 7-point
Likert scale for attitude (based on previous literature [39]) as significant at p < 0.05. The sample cannot be
considered representative of the Dutch population, as oversampling for the smokers and e-cigarette users
was performed in order to achieve sufficient observations. Participants were asked to provide consent
before the start of the survey. Parents of panelists under the age of 18 had previously provided consent for
participation of their child in research questionnaires. Overall, 1307 surveys were completed, and the
response rate was 10.3% (69.7% for adults, n = 694; 5.2% for adolescents, n = 613). For the current study,
respondents were eligible if they met the definition of one of the following user groups (see Supplementary
file 1 for the survey items used [38]): never-users are participants who reported to never have smoked and
never used an e-cigarette; smokers are participants who reported to currently exclusively use cigarettes on
a daily or weekly basis; dual users are participants who reported to currently simultaneously use cigarettes
on a daily or weekly basis and e-cigarettes on a daily or weekly basis; vapers are participants who reported
to currently exclusively use e-cigarettes on a daily or weekly basis [40].
It should be noted that these definitions, similar to studies performed before [39], includes individuals
who had no history of smoking prior to becoming an exclusive vaper. In addition, and due to the cross-
sectional nature of the data, no transitory phases for dual users and exclusive vapers can be determined
[40]. We aimed for mutually exclusive groups. Hence, as the group of exclusive vapers may also include
former smokers and the group of exclusive smokers may also include former vapers, former users were not
included as a separate group. An overview of the items used to determine whether respondents met our
definitions can be found in Supplementary file 1 [38]. In total, 728 participants met the eligibility criteria of
this study. Of those, 394 were adults (62.4% female) and 334 were adolescents (46.7% female).
2.2. Survey
The current study included measures on basic demographics, attractiveness of e-cigarettes, flavor
preferences, and individual factors related to vaping. The survey included routing to ensure that
participants were asked about relevant items only (e.g., never-users were not asked which flavor their first
e-cigarette had). A full overview of the items and concepts is available in Supplementary file 1 [38].
First, participants were asked about basic demographics, and smoking and vaping characteristics
[19,24,40–44]. Educational level was determined based on the Dutch version of the International Standard
Classification of Education (ISCED) [45].
Second, participants were asked to evaluate the attractiveness of eight product characteristics of e-
cigarettes from a predetermined list using a check all that apply (CATA) approach that was based on
previous research [19,24]. For the items that were used to assess demographics and attractiveness of product
characteristics, see Supplementary file 1 [38].
Third, interest in trying an e-liquid flavor (for never-users and smokers), and the first and current e-
liquid flavors used (for dual and e-cigarette users) were assessed. For the items that were used to assess
flavor preferences, see Supplementary file 1 [38]. To assess flavor interest among never-users and smokers,
multiple flavor categories [46] (CATA) or the option “none of the flavors” were selected. If the latter answer
option was selected, no flavor category could be selected simultaneously. E-cigarette users and dual users
were asked about their current and first e-liquid flavor used: “Which flavor do you currently use most? If
possible, please specify the name of the flavor” and “Which flavor did you try first? If possible, please
specify the name of the flavor.” For both current and first flavor used, dual users and e-cigarette users could
select only one flavor category [46] and had to specify their choice through an open question. The answer
options for never-users, smokers, dual users and e-cigarette users were: tobacco, menthol/mint, nuts, herbs,
Int. J. Environ. Res. Public Health 2019, 16, 4661 4 of 15
spices, coffee/tea, cocktails, alcohol, other, sodas, sweet (chocolate, vanilla, desserts, or other), fruit, milk
products, candy, floral, unflavored, and none of the flavors. The closed answer options that were used to
assess flavor preference in all user groups were recoded according to the thirteen main categories of the
recently published e-liquid flavor wheel [47], except for the option “none of the flavors”. Recoding the
reported flavor preferences resulted in the in the following thirteen main categories: tobacco (survey item:
tobacco), menthol/mint (survey item: menthol/mint), nuts (survey item: nuts), spices (survey items: herbs,
spices), coffee/tea (survey items: coffee; tea), alcohol (survey items: alcohol, cocktail; alcohol, other), other
beverages (survey items: soda; sweet, other), fruit (survey item: fruit), dessert (survey items: sweet, dessert;
milk product), other sweets (survey items: sweet, chocolate; sweet, vanilla), candy (survey items: sweet,
candy), other flavors (survey items: floral; other) and unflavored (survey item: unflavored). Open answers
from dual and e-cigarette users were assessed by two authors (KR and EK) to support recoding of the closed
answers according to the categories of the e-liquid flavor wheel [47]. In some cases, multiple survey items
were associated with one flavor category (e.g., the survey answer options “sweet, chocolate” and “sweet,
vanilla” were both recoded to the other sweets flavor category). For equal weight of the flavor categories,
each participant could obtain a maximum score of “1” for each flavor category. Thus, participants who
reported being interested in both chocolate- and vanilla-flavored e-liquids received a total score of “1” for
the other sweets flavor category.
Fourth, individual factors related to vaping were assessed (see Supplementary file 1 [38] for the items
that were used). Evidence-based knowledge about smoking and vaping was measured with 12 statements
that were either correct or incorrect. We consider evidence-based knowledge as knowledge that is based on
scientific consensus—that is, information provided by the Dutch National Institute of Public Health and the
Environment (RIVM) and previous research [19,48,49]. The knowledge items were summed (1 = correct, 0
= incorrect; ‘I don’t know’ was categorized as incorrect). Furthermore, a 7-point Likert scale was used to
assess trust in information (two items) [50], perceived susceptibility towards e-cigarettes (three items: item
A, item B, item C) [51,52], severity related to vaping (four items [51,52]), attitude towards e-cigarettes (four
items) [39,48], social influence (one item) [53], deliberation about vaping (three items) [48], and intention to
start using e-cigarettes (one item). A scale was computed for trust in information, severity related to vaping,
attitude towards e-cigarettes, and deliberation of the pros and cons of vaping, by averaging the scores of
the two items for trust (Cronbach’s α = 0.915), the four items for severity (Cronbach’s α = 0.639), the four
items of attitude (Cronbach’s α = 0.927), and the three items for deliberation (Cronbach’s α = 0.656). No scale
could be computed for perceived susceptibility towards e-cigarettes (Cronbach’s α ≤ 0.6)—thus, for each
user group, the three mean scores for perceived susceptibility towards e-cigarettes and the three mean
scores for perceived susceptibility towards cigarettes (for each individual survey item) were used. Similarly,
for each user group, the mean score for each item regarding intention and social influence was determined.
2.3. Data Analysis
IBM statistics SPSS version 24 (IBM, Armonk, NY, USA) [54,55] was used for data analysis. No data
were excluded. Attractiveness of product characteristics, and the e-liquid flavor categories preferred (for
never-users and smokers, excluding those who selected the answer option “I don’t want to try any flavor”)
and firstly and currently used (for dual and exclusive vapers) were analyzed using frequencies. Flavor
preferences were presented in a pie chart as the percentage of the total number of responses.
Spearman correlation analyses showed that age (p < 0.05), gender, and level of education (<0.05) were
significantly associated with individual factors related to vaping. However, these Spearman correlations
were small, ranging from −0.211 to 0.169. Age, level of education, and gender were therefore excluded from
further analyses due to small or non-significant correlations.
Individual factors were compared between both never-users and smokers interested in trying an e-
liquid flavor and those not interested in trying a flavor (answer option: “none of the flavors”) using t-tests.
Results were considered significant if p < 0.05.
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3. Results
Of the 728 never-users, smokers, dual users, and exclusive e-cigarette users, 23.7% was highly educated
(50.0% low education level and 26.2% middle education level), and the average age was 34.1 (± 20.2, min =
13, max = 84) (see Table 1).
3.1. Attractiveness of Product Characteristics
Table 1 shows attractiveness of e-cigarette product characteristics, stratified by user group. From the
e-cigarette product characteristics assessed, all groups reported flavors as the most attractive.
3.2. E-Liquid Flavor Preferences
Of the 407 never-users, 68% selected the option “none of the flavors” (n = 278 participants) and 32%
selected to be interested in trying one or more e-liquid flavor” and 32% (n = 248 responses)). Of the 138
smokers, 20% (n = 27 participants) were interested in none of the flavors and 80% (n = 208 responses) selected
to be interested in trying one or more e-liquid flavor categories.
Figure 1 shows e-liquid flavor preferences as the percentage of each flavor category for never-users
and smokers. Never-users were mostly interested in trying e-liquid flavors from the menthol/mint (19% of
248 responses) and sweet categories, such as other sweets (19%) and fruit (14%). Smokers were mostly
interested in e-liquids with tobacco flavor (30%), followed by menthol/mint (18%) and other sweets (9%).
Of the 122 dual users, 120 reported the flavor of their first e-cigarette used and 121 reported the flavor
they currently use (see Figure 2). Of the 61 exclusive vapers, 58 reported the flavor of both their first and
current e-cigarette. Among dual users, the most frequently reported flavors of their current and first e-
cigarette used were similar: tobacco (52% vs. 53%), menthol/mint (26% vs. 27%), other sweets (10% vs. 11%),
and fruit (7% vs. 6%). Among exclusive vapers, differences were observed in the most frequently reported
flavors of their current and first e-cigarette used: tobacco (43% vs. 53%), menthol/mint (19% vs. 28%)), and
fruit (14% vs. 9%) and other sweets (14% vs. 7%).
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Table 1. Participants’ demographics and the attractiveness of e-cigarette product characteristics. Data are presented for adult and adolescent never-users (n = 407),
smokers (n = 138), dual users (n = 122), and exclusive vapers (n = 61).
Participants’ demographics and the attractiveness of e-cigarette product characteristics Never-users
(n = 407)
Smokers
(n = 138)
Dual users
(n = 122)
Exclusive vapers
(n = 61)
Mean age (±SD) 31 (18.6) D 35 (20.6) 37 (18.8)
N 37 (19.4)
Gender Male 44.0% 37.7% 53.3% 49.2%
Female 56.0% 62.3% 46.7% 50.8%
Education
Low 52.1% 52.9% 43.4% 39.3%
Middle 20.6%
D,E 30.4% 35.2%
N 44.3% N
High 27.3% 16.7% 21.3% 16.4%
Attractive characteristics of e-cigarettes (%)
All the different flavors 10.3% 30.4% 34.4% 68.9%
The product looks nice 6.6% 19.6% 22.1% 44.3%
The nicotine level can be varied 4.7% 13.8% 15.6% 31.1%
It is possible to alter the setting of the e-cigarette to my wishes 3.7% 10.9% 12.3% 24.6%
Its varying designs 3.2% 9.4% 10.7% 21.3%
You can blow nice smoke clouds with it (cloud chasing) 2.5% 7.2% 8.2% 16.4%
Price of the product 2.0% 5.8% 6.6% 13.1%
Price of the e-liquids 2.0% 5.8% 6.6% 13.1%
N,D,E Superscripts indicate significant differences in a row between user groups (p < 0.05), with N = never-users, D = dual users, and E = exclusive vapers. Significant
differences between user groups were determined for age, gender, and education using Bonferroni post-hoc corrections. General note: due to rounding, percentages
may not add up to 100%.
Int. J. Environ. Res. Public Health 2019, 16, 4661 7 of 15
Figure 1. Interest in trying e-liquid flavors among never-users (left) and smokers (right). Never-users
(n= 278; 68%) and smokers (n = 27; 20%) who selected the option “none of the flavors” were excluded
from this visualization, and hence the pie charts visualize 248 responses from 32% of the never-users
and 208 responses from 80% of the smokers. Data are presented as percentages of the total number of
responses, not of the total sample sizes.
Figure 2. Flavors used on current (top) and first (bottom) e-cigarette exposure among dual (left) and
exclusive vapers (right). Participants could select only one flavor category to indicate the flavor of
their current and first e-cigarette used. Data are presented as percentages of the total number of
responses, not of the total sample sizes.
Int. J. Environ. Res. Public Health 2019, 16, 4661 8 of 15
3.3. Individual Factors Related to Vaping
Table 2 shows differences in individual factors related to vaping between never-users and
smokers. In addition, differences within the groups of never-users and smokers between those who
were interested in trying an e-liquid flavor and those who did not want to try any flavor are shown.
Never-users who were interested in trying a flavor had significantly less knowledge about e-
cigarettes compared to never-users who did not want to try any e-liquid flavor (p < 0.05). Not
surprisingly, never-users and smokers who were interested in trying a flavor were significantly more
positive towards e-cigarettes and had a significant higher intention to start vaping, compared to
never users and smokers who reported not wanting to try any e-liquid flavor (p < 0.05), within both
never-users and smokers. Never-users who were interested in trying a flavor reported a lower
perceived susceptibility (item C) than never-users who did not want to try a flavor (p < 0.05). In
addition, smokers who were interested in trying a flavor considered the social influence towards not
using e-cigarettes as less strong, which means that the smokers who were not interested in trying an
e-cigarette flavor more often find that society thinks that one should not vape (p < 0.05).
Table 2. Individual factors related to vaping. Data are presented for never-users and smokers.
Individual factors related to
vaping
Never-users
(n = 407)
Smokers
(n = 138)
Knowledge about e-
cigarettes and cigarettes
(±SD)
Overall 9.3 (1.5) * 8.4 (1.8) *
Those interested in trying a flavor 8.9 (1.7) ° 8.4 (1.7)
Those who did not want to try any flavor 9.4 (1.4) ° 8.3 (2.1)
Trust in information (±SD)
Overall 5.2 (1.1) 4.9 (1.4)
Those interested in trying a flavor 5.2 (1.0) 4.9 (1.4)
Those who did not want to try any flavor 5.2 (1.4) 5.1 (1.5)
Perceived susceptibility
about vaping (±SD)
A Overall 4.9 (1.3) * 4.3 (1.2) *
Those interested in trying a flavor 4.8 (1.3) 4.2 (1.2)
Those who did not want to try any flavor 4.9 (1.3) 4.4 (1.2)
B Overall 5.0 (1.2) * 4.3 (1.2) *
Those interested in trying a flavor 4.8 (1.2) 4.3 (1.2)
Those who did not want to try any flavor 5.1 (1.2) 4.5 (1.2)
C Overall 4.9 (1.2) * 4.3 (1.2) *
Those interested in trying a flavor 4.8 (1.3) ° 4.2 (1.2)
Those who did not want to try any flavor 5.0 (1.2) ° 4.6 (1.2)
Severity of vaping (±SD)
Overall 4.6 (1.1) * 4.4 (1.1) *
Those interested in trying a flavor 4.6 (1.1) 4.4 (1.2)
Those who did not want to try any flavor 4.6 (1.1) 4.1 (1.1)
Attitude towards e-
cigarettes (±SD)
Overall 2.1 (1.1) * 3.5 (1.1) *
Those interested in trying a flavor 2.6 (1.2) ° 3.7 (1.0) °
Those who did not want to try any flavor 1.9 (1.0) ° 2.9 (1.2) °
Social influence (±SD)
Overall 5.1 (1.7) * 4.4 (1.5) N
Those interested in trying a flavor 4.9 (1.7) 4.2 (1.5) °
Those who did not want to try any flavor 5.2 (1.7) 5.1 (1.2) °
Deliberation on the pros
and cons of e-cigarette use
(±SD)
Overall 2.8 (1.5) 3.0 (1.5)
Those interested in trying a flavor 2.9 (1.6) 3.1 (1.4)
Those who did not want to try any flavor 2.7 (1.5) 2.7 (1.7)
Intention to start vaping
(±SD)
Overall 1.2 (±0.8) * 2.5 (±1.7) *
Those interested in trying a flavor 1.4 (1.1) ° 2.7 (1.7) °
Those who did not want to try any flavor 1.1 (0.6) ° 1.6 (1.4) °
* Indicates significant differences (p < 0.05) in a row between user groups. ° Indicates a within-group
significant difference (p < 0.05) between those who were interested in trying any e-liquid flavor and
those who were not interested in trying any e-liquid flavor (only for never-users and smokers).
Knowledge was determined using 12 statements. A higher score represents more knowledge, with 0
= no correct answers and 12 = correct answers for all statements. Trust was assessed with two items,
using a 7-point Likert scale; 1 low to 7 = high level of trust in information provided. Perceived
susceptibility assessed the chance of developing cancer as a result of vaping with three statements:
Int. J. Environ. Res. Public Health 2019, 16, 4661 9 of 15
(A) If I vape, then my risk of developing some form of cancer during my lifetime is…; (B) I think that
if I vape, my chance of developing some form of cancer during my lifetime is …; (C) My feeling is that
if I vape, the chance of developing some form of cancer during my lifetime is…; 1 = low to 7 =
perception of cognitive risk of health risks related to e-cigarette use. Severity was assessed with four
items, on a 7-point Likert scale ranging from very bad to not bad at all (1–7); Attitude was assessed
with four items, using a 7-point Likert scale, with 1 = very negative towards e-cigarette use and 7 =
very positive towards e-cigarette use. Deliberation was assessed with three items on a 7-point Likert
scale, with 1 = no deliberation about E-cigarette use to 7 = very extensive deliberation about E-cigarette
use. Intention to start vaping was reported on a 7-point Likert scale, with 1= very low intention to
start vaping and 7 = very high intention to start vaping.
4. Discussion
This study shows that the availability of different flavors was reported to be the most attractive
product characteristic of e-cigarettes by all user groups, and that flavor preferences differ between
never-users, smokers, dual users, and exclusive vapers. The first e-cigarette used by dual users and
vapers mostly had a tobacco or menthol/mint flavor, but compared to dual users, we observed that
exclusive vapers use more sweet- and fruit-flavored e-liquids than dual users. While tobacco was the
most appealing flavor category among smokers, never-users were mostly interested in trying
menthol- and sweet-flavored e-liquids. In addition, individual factors related to vaping differed
within the groups of never-users and smokers. That is, never-users interested in trying a flavor had
less knowledge about cigarettes and e-cigarettes than those who did not want to try any flavor.
Attitude was more positive, and intention to start vaping was higher among both never-users and
smokers who were interested in trying a flavor compared to those not interested in trying a flavor.
Perceived susceptibility of health consequences was lower among never-users who were interested
in trying a flavor, and social influence regarding not using e-cigarettes was lower among smokers
who were interested in trying a flavor. Thus, similarly to the role of flavors in food choice [31,32], our
results indicate that interest in flavors may moderate the differences in individual factors related to
vaping.
While concerns have been raised about potential e-cigarette use among never-users [3,9,56], the
never-users in our study had a low intention to start vaping and more than two-third (68%) of the
never-users did not want to try any e-liquid flavor. However, nearly one-third of the never-users
were still interested in trying an e-liquid flavor. Not surprisingly, they perceived a lower
susceptibility towards negative health consequences of vaping, had a more positive attitude towards
e-cigarettes, less knowledge about cigarettes and e-cigarettes, and a higher intention to start vaping
than never-users who did not want to try any flavor. It should, however, be noted that a causal
relation between these findings was not examined. For example, never-users could report to find e-
liquid flavors interesting because they were already interested in trying e-cigarettes. On the other
hand, they may have become interested in trying e-cigarettes because of the appealing flavors that
they recognize from palatable food products. This means that being interested in flavors has a
positive effect on the decision to start using e-cigarettes, or vice versa. Nevertheless, our findings
regarding the interest of never-users in e-liquid flavors indicate that never-users may be vulnerable
to flavor marketing of e-cigarettes [26,27,57,58]. For example, marketing of appealing e-liquid flavors
may make never-users even more positive towards vaping, thereby potentially influencing their
choice to initiate or refrain from vaping [19]. This suggests that the reverse can also be true: adapting
product characteristics, for example restricting e-liquid flavors or regulating other product
characteristics, may reduce attractiveness and consequently make never-users more negative about
vaping. Some characteristics of e-liquids are currently regulated by Tobacco Regulation in the
Netherlands [59,60]. However, legislation regarding e-liquid flavors currently does not exist. Further
research is needed to help regulators decide whether and how the regulation of e-liquid flavors can
improve public health.
This study showed that smokers who were interested in trying an e-liquid flavor had a more
positive attitude towards e-cigarettes than smokers who were not interested in trying a flavor. In
addition, smokers who were interested in trying a flavor considered the social influence towards not
Int. J. Environ. Res. Public Health 2019, 16, 4661 10 of 15
using e-cigarettes as less strong, which means that the smokers who were not interested in trying an
e-cigarette flavor more often find that society thinks that one should not vape. Furthermore, two-
third of the smokers reported interest in an e-liquid flavor other than tobacco. This indicates that
flavors could support the decision of smokers to switch to vaping [58], for example by allowing the
marketing of e-liquid flavors and other product characteristics that smokers find attractive [4]. The
role of e-liquid flavors in supporting both the decision to switch towards e-cigarette use (for smokers)
and to refrain from using e-cigarettes (for never-users) demonstrates the complexity of developing
future regulations on e-liquid flavors.
Additional support for the interest in flavors moderating differences in individual factors related
to vaping is provided by the different patterns of e-liquid flavors used by dual users and exclusive
vapers. In line with previous research, both groups mostly used tobacco and mint flavored e-
cigarettes at initiation, but exclusive vapers currently used more fruit and sweet e-liquid flavors than
dual users [5,34,61–63]. This could be interpreted as vapers switching from tobacco to non-tobacco
flavors over time, which is supported by a previous study [5]. Because most adult exclusive vapers
included in this study used e-cigarettes for 1 to 5 years and most dual users reported to vape for only
less than 6 months (data not shown), it is possible that the dual users may switch to fruit or sweet e-
liquid flavors in the future. Longitudinal research is needed to investigate whether and how e-liquid
flavors could support dual users in their decision to switch to exclusive vaping. In addition, it would
be interesting to investigate the process of e-liquid flavors (or other product characteristics)
eventually not living up to dual users’ expectation, thereby leaving them to quit vaping and relapse
into exclusive cigarette smoking. This information could be used to, for example, stimulate an
exchange of knowledge and experiences between exclusive vapers and dual users about the flavored
e-liquids they use [64].
4.1. Future Research
Previous studies assessing individual factors related to vaping mostly focused their survey items
on e-cigarettes in general. This means that participants are typically asked about their mental
representation or beliefs of an unspecified e-cigarette, thereby not taking into account that the e-
cigarette is a product that is available in various shapes, sizes, colors, flavors, and more. As our results
suggest that flavors may moderate the differences in individual factors related to vaping, we
recommend using survey items that represent a specific flavor or other product characteristic. For
example, instead of only focusing on perceived susceptibility attitude towards e-cigarettes in general
[65,66], researchers should also assess perceived susceptibility attitudes towards a specific e-liquid
flavor categories, such as fruit, candy, and tobacco [47].
In addition, as other product characteristics may moderate differences found in individual
factors related to vaping, the impact of for example price, labeling, and packaging of e-cigarettes and
e-liquids on individual factors related to vaping should be investigated in different user groups [67]
to determine which characteristics make up their “ideal” e-cigarette.
Furthermore, it would be interesting to use sensory research to investigate differences in e-liquid
flavor liking between user groups, and how this relates to individual factors related to vaping.
Finally, research is needed to investigate the interaction between product characteristics and
individual factors related to new and emerging products, such as heated tobacco products and
products containing nicotine salts. This will provide insight into which specific product
characteristics are most appealing to vulnerable user groups, such as never-users and youth, and thus
need to be regulated.
4.2. Limitations
Ideally, our sample size would be large enough to stratify our sample into different age groups
and different flavor categories. However, our sample size was too small to determine differences in
the preference of specific flavor categories between age groups (adults vs. adolescents), and
differences in individual factors related vaping between specific flavor categories. In addition,
response rates among adolescents was very low, and the rather high education level of participants
Int. J. Environ. Res. Public Health 2019, 16, 4661 11 of 15
in this study was not be representative of the Dutch population [68,69]. In addition, the sample cannot
be considered representative of the Dutch population, as oversampling for the smokers and e-
cigarette users was performed in order to have sufficient observations. As a result, the percentages
of smokers and vapers in our study do not reflect the actual percentages of smokers and vapers in
the Dutch population.
5. Conclusions
This study demonstrates that being interested in flavors moderates the differences in individual
factors related to vaping for never-users and smokers, or vice versa. While the availability of different
flavors was reported to be the most attractive product characteristic of e-cigarettes in all user groups,
the specific flavor preferences varied between never-users, smokers, dual users, and exclusive vapers.
Importantly, individual factors related to vaping (knowledge, perceived susceptibility attitude, social
influence, and intention to start vaping) differed between never-users and/or smokers who were
interested in trying an e-liquid flavor and those who did not want to try a flavor. Our results confirm
the importance and complexity of regulating e-liquid flavors in a way that both the decision to switch
towards vaping (for smokers) and the decision to refrain from vaping (for never-users) are supported.
Ideally, regulation should allow marketing of e-liquid flavors that stimulate smokers and dual users
to keep or start using e-cigarettes. To make never-users more negative about and keep them from
using e-cigarettes, product appeal should be reduced by, for example, restricting the marketing and
promotion of e-liquid flavors that they find particularly appealing.
Supplementary Materials: The following are available online at www.mdpi.com/xxx/s1, Supplementary file 1
was previously described in Romijnders, Pennings, van Osch, de Vries and Talhout [38].
Author Contributions: K.A.G.J.R. and E.J.Z.K. contributed equally. Conceptualization: K.A.G.J.R., E.J.Z.K.,
H.d.V., and R.T.; methodology, K.A.G.J.R.; formal analysis, K.A.G.J.R. and E.J.Z.K.; data curation, K.A.G.J.R.;
writing—original draft preparation, K.A.G.J.R. and E.J.Z.K.; writing—review and editing, K.A.G.J.R., E.J.Z.K.,
H.d.V., S.B., K.d.G., and R.T.; visualization, E.J.Z.K.; supervision, H.d.V., S.B., K.d.G., and R.T.
Funding: This research received no external funding but was supported by the Dutch National Institute for
Public Health and the Environment (RIVM) (grant number S132006).
Acknowledgments: We gratefully thank the study participants for their time and thoughtful consideration, and
we thank Selma Eising for her critical feedback on the manuscript. The authors would also like to thank Liesbeth
van Osch for her valuable contribution during the conceptualization of this study.
Conflicts of Interest: The authors declare no conflict of interest.
Int. J. Environ. Res. Public Health 2019, 16, 4661 12 of 15
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