Patterns of flavored e-cigarette use at the time of quitting smoking: comparison between American young adults (18–24 years old) and older adults (> 24 years old)

Abstract

Background

Flavored e-cigarettes remain a controversial public health topic, with disagreement on their potential benefits and harms. In this study we compared patterns of flavor use in e-cigarettes at the time of quitting smoking between young adults (18–24 years old) with older adults (> 24 years old).

Methods

A convenience sample of US adults who formerly smoked and reported consuming e-cigarettes every day or some days during the period of quitting smoking were included in the study (N = 51,641) and responded to an online questionnaire. Participants were divided into young adults (n = 9895) and older adults (n = 41746).

Results

The most popular flavors used regularly by young adults and older adults were fruit (92.3% and 81.3%, P < 0.001), followed by dessert/pastry/bakery (67.3% and 68.1%, P = 0.054) and candy/chocolate/sweet (49.7% and 43.3%, P < 0.001). Fruit was the most prevalent single most often used flavor for both groups but was more prevalent in young adults (63.4% vs. 46.0% in older adults, P < 0.001), followed by dessert/pastry/bakery which was more prevalent in older adults (32.1% vs. 22.7% in young adults, P < 0.001). Menthol and mint/wintergreen flavors, while the fourth and fifth most popular flavors used regularly, were the single most often used flavors by only a small minority in both groups. Tobacco flavor was the single most often used flavor by 1.1% of young and 6.0% of older adults (P < 0.001). From logistic regression analysis, being a young adult was positively associated with the use of fruit (OR: 1.65, 95% CI 1.16–2.35), menthol (OR: 1.58, 95% CI 1.09–2.30), mint/wintergreen (OR: 1.51, 95% CI 1.00-2.28) and non-alcoholic/non-coffee drink (OR: 1.83, 95% CI 1.18–2.83) flavors, and negatively associated with the use of tobacco (OR: 0.52, 95% CI 0.34–0.78) flavor at the time of quitting smoking.

Conclusion

Non-tobacco flavors were popular among the US adult former-smoking e-cigarette consumers at the time of quitting smoking, but different flavor preferences exist between young and older adults. Tobacco flavor use prevalence was low, as were menthol and mint/wintergreen, particularly as the single most often used flavors. Future studies should explore patterns of e-cigarette flavor use in young adults who smoke or used to smoke, in addition to those with no smoking history.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12954-025-01343-4.

Background

The growing popularity of electronic cigarettes (e-cigarettes) over the past few years has raised concerns over the fact that these products are available in a large number of flavor combinations [1–3]. Flavoring additives are a necessary component of e-cigarette liquids because the rest of the ingredients (usually propylene glycol, glycerol and nicotine) are flavorless. Since the early years of e-cigarette marketing, a large variety of flavors have been available, not limited to tobacco-like flavors but also including other types such as fruits, drinks, sweets, beverages and others. Studies suggest a gradual transition over time since e-cigarette use initiation, from tobacco to non-tobacco flavors, while people who exclusively use e-cigarettes and have quit smoking appear to be more likely to use non-tobacco flavors compared to those who still smoke and use e-cigarettes (dual use) [4–6].

The availability and variability of non-tobacco flavors has been the main reason for criticism by public health scientists and authorities, fearing that such products could be appealing to youth and young adults who represent the main vulnerable groups in becoming dependent on nicotine and even initiate smoking. Some suggest there is a “gateway to smoking” effect for e-cigarettes, which could be attributed to flavors [7–12], although usually such studies do not account for the common liability model of explaining behaviors [13]. At the same time, youth and younger adults are more likely to use non-tobacco flavors compared to older adults [14, 15]. Thus, it has been suggested that flavors may be one of the main drives for e-cigarette use among younger people. The concerns about e-cigarettes being appealing to youth and young adults through their flavor profile has led to discussions or even already-established regulatory initiatives to restrict flavor variability, mainly by allowing only tobacco flavors to be marketed. However, the main focus of research examines e-cigarette flavors use among younger people who have not smoked but has not addressed the issue of flavor choices among those who smoke or who have quit smoking.

Considering the above, the purpose of this study was to examine the patterns of e-cigarette flavor use in a convenient sample of Americans who reported having formerly smoked and having used e-cigarettes at the time of quitting, comparing young adults (18–24 years old) with older adults (> 24 years old).

Methods

Study sample and online platform

The study sample has been presented previously [16]. In brief, individuals aged 18 years and older living in the US who had ever used an e-cigarette were invited to complete an online questionnaire available through Dacima Survey software (Dacima, Montreal, Quebec, Canada). Before entering the main survey questionnaire, participants had to read and agree to an informed consent. The questionnaire was open for participation from April 3rd to May 2nd, 2018. Double entries were excluded by recording the IP addresses of the participants. No financial or other incentive was offered in exchange for participation. The study was approved by the ethics committee of the University of Patras in Greece.

Participants and questionnaire design

All participants were ever e-cigarette consumers. Through a detailed assessment of their past and current smoking status, only participants who reported having formerly smoked, defined as those who had ever smoked (even 1 or 2 puffs) but had not smoked in the past 30 days, were selected for this study. An additional inclusion criterion was that they should have been using e-cigarettes (every day or on some days) at the time of quitting smoking. The specific question was: “Thinking back to when you quit smoking cigarettes completely, were you using an e-cigarette/ vaping device…”, with response options being “Every day”, “Some days” and “Not at all”. In total, 51,641 subjects fulfilled the inclusion criteria. Based on their age, the subjects were divided into two groups: young adults (aged 18–24 years) and older adults (aged > 24 years).

Participants were asked about their past cigarette consumption and time since quitting smoking. The patterns of e-cigarette flavor use at the time quitting smoking was examined by asking the flavor choices used regularly, with the participants having the option to choose more than one flavor, and the single most often used flavor. For all questions on flavor choices, a pre-determined list of 12 flavor types was provided, specifically tobacco, menthol, mint/wintergreen, fruit, dessert/pastry/bakery, candy/chocolate/sweet, spice, coffee, alcohol/cocktail, non-alcoholic/non-coffee drink, unflavored and other. Additionally, they were asked to report which flavors were particularly helpful to avoid relapse to smoking and whether finding an e-cigarette/e-liquid flavor they liked was important in their attempt to quit smoking. The latter question had a response option in the form of a Likert scale, with options being “Extremely important”, “Very important”, “Important”, “Slightly important” and “Not important”. Additional questions were used to examine e-cigarette nicotine concentration and type of device used at the time of quitting smoking.

Statistical analysis

Descriptive analysis was performed with the data presented as median and interquartile range (IQR) for continuous variables, and proportions (%) and number (n) for categorical variables. Comparisons between the two age groups were performed using cross-tabulations and chi-square tests with z-test to compare column proportions with Bonferroni correction. Mann Whitney U-test was used to compare the duration of quitting smoking and the cigarette consumption when smoking between groups. Logistic regression analyses were performed to examine the odds of regular use of each e-cigarette flavor at the time of quitting smoking as well as of each single e-cigarette flavor used most often at the time of quitting smoking. In both regressions, age was the dependent variable, and the models were adjusted for demographics (residence state, gender, race/ethnicity, marital status, employment status, education and annual household income), nicotine concentration in e-cigarettes and type of device used at the time of quitting smoking, cigarette consumption when smoking and smoking cessation duration. Two models were prepared, one for regularly used flavors and another for the single most often used flavor. Further sensitivity analysis was performed comparing age group 18–24 years with the slightly older age group of 25–34 years. All analyses were performed with commercially available software (SPSS v. 22, Chicago IL, USA) and a p value of < 0.05 was considered statistically significant.

Results

Descriptive analysis for all participants

The study sample consisted of 9895 young adults and 41,746 older adults. The reported residence state of participants is presented in Supplementary Table 1. Only 0.8% (n = 388) did not report their residence state (missing data). The demographic data for each group is presented in Table 1. Statistically significant differences were observed between groups in all variables.

Table 1.

Participant demographics (n = 51,641)

	Young adults		Older adults		P value
	%	n	%	n
Sex
Male	80.8%	7998	72.6%	30,327	< 0.001
Female	18.2%	1799	26.4%	11,012
Transgender	0.7%	67	0.3%	143
Race-ethnicity
White/non-Hispanic	60.3%	5967	55.2%	23,042	< 0.001
White/Hispanic	26.5%	2624	30.1%	12,586
Black/African American	2.9%	291	2.9%	1129
Other	10.2%	1013	11.9%	4986
Marital status
Married	11.1%	1097	50.0%	20,889	< 0.001
Never married	87.2%	8629	32.3%	13,489
Divorced	1.0%	102	13.8%	5754
Separated	0.4%	43	2.5%	1037
Widowed	0.1%	5	1.0%	421
Employment status
Not currently working for pay	15.3%	1515	16.2%	6771	< 0.001
Full-time working, at least 35 h/week	61.5%	6090	75.6%	31,575
Part-time working, 15–34 h/week	19.5%	1929	6.3%	2620
Part-time working, < 15 h/week	3.4%	341	1.5%	614
Education
Less than high school	1.2%	115	0.7%	308	< 0.001
Some high school, no diploma	5.0%	498	3.6%	1487
GED	5.6%	553	8.4%	3505
High school graduate—diploma	40.8%	4040	20.9%	8716
Some college but no degree	32.7%	3235	33.3%	13,912
Associate degree—occupational/vocational	4.9%	487	10.9%	4541
Associate degree—academic program	4.0%	396	6.0%	2498
Bachelor’s degree (ex: BA, AB, BS)	4.7%	463	11.3%	4703
Master’s degree (ex: MA, MS, MEng, Med, MSW)	0.3%	29	2.5%	1050
Professional school degree (ex: MD, DDS, DVM, JD)	0.2%	17	0.6%	243
Doctorate degree (ex: PhD, EdD)	0.2%	19	0.3%	137
Household income per 12 months
Less than $10,000	11.8%	1163	4.3%	1777	< 0.001
$10,000 to $14,999	11.3%	1118	4.4%	1834
$15,000 to $24,999	17.8%	1758	9.1%	3780
$25,000 to $34,999	15.6%	1548	12.4%	5178
$35,000 to $49,999	13.5%	1333	16.5%	6886
$50,000 to $74,999	11.5%	1140	20.8%	8689
$75,000 to $99,999	6.3%	626	12.0%	5029
$100,000 to $149,999	5.3%	524	9.7%	4033
$150,000 to $199,999	1.7%	165	2.8%	1163
$200,000 or more	1.7%	171	2.0%	834

Participants were consuming a median of 20 (IQR: 15–30) cigarettes per day when smoking, with young adults having lower consumption than older adults (10, IQR: 5–20 vs. 20, IQR: 15–30 respectively, P < 0.001). Additionally, they had quit smoking for a median of 37 (IQR: 23–60) months, with young adults having lower quit duration than older adults (24, IQR: 12–38 vs. 43, IQR: 24–61 respectively, P < 0.001).

Table 2 presents the e-cigarette consumption patterns, equipment and flavor use by the study sample at the time of quitting smoking. The vast majority of participants reported using e-cigarettes every day at the time of quitting smoking, with slightly but statistically significant higher proportion for older than young adults. Most subjects reported they would have definitely or probably be smoking at the time of the survey had they never initiated e-cigarette consumption. Most were using advanced personal vaporizers (with adjustable power settings), with a higher proportion observed in younger compared to older adults. Very few were using non-nicotine liquids at the time of quitting smoking, while the most popular nicotine concentration range used was 1–6 mg/mL for both groups. Participants suggested that finding an e-cigarette flavor they liked was important in their attempt to quit smoking, and thought that fruit and dessert/pastry/bakery were most helpful in quitting smoking.

Table 2.

E-cigarette consumption patterns, equipment and flavors use by adults who formerly smoked, at the time they quit smoking (n = 51,641)

	Young adults		Older adults		P value
	%	n	%	n
Frequency of e-cigarette use at the time of quitting smoking
Every day	87.1%	8616	94.2%	39,317	< 0.001
Some days	12.9%	1279	5.8%	2429
If you had never started using e-cigarettes, would you still be smoking today?
Definitely yes	64.2%	6357	74.0%	30,908	< 0.001
Probably yes	28.2%	2792	22.9%	9567
Probably no	3.3%	326	1.3%	555
Definitely no	4.2%	420	1.7%	716
Device used most often at the time of quitting smoking
Disposable	1.1%	112	2.1%	893	< 0.001
Rechargeable ciga-like with prefilled cartridges	7.0%	690	10.4%	4354
eGo-style	15.0%	1489	29.6%	12,338
Pod mod	2.3%	228	1.0%	397
Mechanical device	7.0%	695	4.7%	1971
Variable voltage/wattage (advanced personal vaporizer)	66.5%	6583	51.5%	21,498
Something else	1.0%	98	0.7%	298
Nicotine concentration at the time of quitting smoking
0 mg/mL	3.3%	326	1.1%	472	< 0.001
1–6 mg/mL	69.4%	6867	41.6%	17,353
7–12 mg/mL	13.5%	1339	20.7%	8634
13–17 mg/mL	2.2%	215	4.7%	1946
18–24 mg/mL	7.0%	690	26.9%	11,237
25–49 mg/mL	1.5%	147	3.0%	1271
50 mg/mL or more	1.8%	179	0.4%	186
Don’t remember	1.3%	132	1.5%	647
How important was finding an e-cigarette/e-liquid flavor you liked in your attempt to quit smoking?
Extremely important	65.4%	6476	70.7%	29,503	< 0.001
Very important	17.8%	1764	17.5%	7306
Important	10.8%	1066	8.2%	3442
Slightly important	4.2%	415	2.8%	1164
Not important	1.8%	174	0.8%	331
Flavors choices (used regularly) at the time of quitting smoking
Tobacco	7.2%	716	16.9%	7047	< 0.001
Menthol	24.4%	2419	16.7%	6975	< 0.001
Mint/wintergreen	15.4%	1524	10.6%	4410	< 0.001
Fruit	92.3%	9134	81.2%	33,878	< 0.001
Dessert/pastry/bakery	67.3%	6659	68.1%	28,447	0.054
Candy/chocolate/sweet	49.7%	4917	43.3%	18,069	< 0.001
Spice	8.5%	837	9.9%	4114	< 0.001
Coffee	20.7%	2049	19.8%	8249	0.018
Alcohol/cocktail	7.3%	718	5.6%	2332	< 0.001
Non alcoholic/non coffee drink	19.9%	1972	11.5%	4794	< 0.001
Unflavored	1.1%	107	0.6%	242	< 0.001
Other	13.9%	1372	8.1%	3389	< 0.001
Number of flavors used at the time of quitting smoking	3	2–5	4	2–5	0.081
Single flavor used most often at the time of quitting smoking
Tobacco	1.1%	109	6.0%	2508	< 0.001
Menthol	4.5%	450	4.7%	1980	0.212
Mint/wintergreen	1.7%	165	1.6%	676	0.383
Fruit	63.4%	6278	46.0%	19,205	< 0.001
Dessert/pastry/bakery	22.7%	2244	32.1%	13,413	< 0.001
Candy/chocolate/sweet	3.7%	370	4.2%	1735	0.032
Spice	0.3%	31	1.3%	562	< 0.001
Coffee	0.7%	74	2.1%	879	< 0.001
Alcohol/cocktail	0.2%	15	0.3%	127	0.006
Non alcoholic/non coffee drink	1.1%	104	0.9%	372	0.075
Unflavored	0.0%	3	0.1%	37	0.037
Other	0.5%	52	0.6%	252	0.200
Flavors choices that were particularly helpful to avoid relapse to smoking
None in particular	2.9%	291	2.4%	998	0.001
Tobacco	4.3%	430	8.1%	3362	< 0.001
Menthol	17.1%	1695	10.1%	4230	< 0.001
Mint/wintergreen	13.0%	1286	7.8%	3239	< 0.001
Fruit	79.7%	7886	70.3%	29,358	< 0.001
Dessert/pastry/bakery	59.3%	5872	62.5%	26,086	< 0.001
Candy/chocolate/sweet	45.5%	4498	39.5%	16,483	< 0.001
Spice	8.9%	880	9.2%	3855	< 0.001
Coffee	20.3%	2010	18.8%	7847	< 0.001
Alcohol/cocktail	8.4%	828	6.2%	2597	< 0.001
Non alcoholic/non coffee drink	19.6%	1936	11.3%	4705	< 0.001
Unflavored	1.1%	107	0.6%	256	< 0.001
Other	13.5%	1333	8.3%	3483	< 0.001

A median of 4 (IQR: 2–5) different flavors were used at the time of quitting by the study subjects, with no statistically significant differences between groups. The most commonly used flavors in the whole study sample and in each group separately were fruit (83.3% of all participants), followed by dessert/pastry/bakery (68.0%), candy/chocolate/sweet (44.5%), coffee (19.9%) and menthol (18.2%). Fruit, dessert/pastry/bakery, coffee and menthol were more prevalent in young compared to older adults. Tobacco flavor use was reported by 15.0% of the participants, with more than double the prevalence of use in older compared to younger adults. Fruit was the most popular single most often used flavor overall (49.3% of the total sample) and for both groups, but it was more prevalent in younger compared to older adults. Dessert/pastry/bakery was the second most popular flavor (30.3% overall), but was more prevalent in older compared to younger adults. Tobacco was the single most often used flavor for 5.1% of the sample, but use by older adults was almost 6-fold more prevalent (6.0%) compared to younger adults (1.1%). Use of unflavored liquids was rare.

Table 3 displays the logistic regression analysis presenting the odds of regular use of each e-cigarette flavor at the time of quitting smoking for younger compared to older adults (using the question in which participants could chose more than one flavor). Younger adults were more likely to use menthol, mint/wintergreen, fruit, non-alcoholic/non-coffee drink and other flavors, and less likely to use tobacco, dessert/pastry/bakery, and spice flavors. Table 4 displays the logistic regression analysis presenting the odds of single most often used e-cigarette flavor at the time of quitting smoking for younger compared to older adults. Younger adults were more likely to use menthol, mint/wintergreen, fruit and non-alcoholic/non-coffee drink, and less likely to use tobacco flavors.

Table 3.

Logistic regression analysis presenting the odds of regular use of each e-cigarette flavor at the time of quitting smoking for younger adults (18–24 years old) compared to older adults (> 24 years old)

	OR	95% CI	P value
Tobacco	0.71	0.64–0.78	< 0.001
Menthol	1.61	1.50–1.73	< 0.001
Mint/wintergreen	1.32	1.21–1.44	< 0.001
Fruit	1.80	1.63–1.97	< 0.001
Dessert/pastry/bakery	0.83	0.78–0.89	< 0.001
Candy/chocolate/sweet	1.02	0.96–1.08	0.570
Spice	0.74	0.67–0.83	< 0.001
Coffee	1.08	1.00-1.16	0.065
Alcohol/cocktail	1.00	0.88–1.13	0.948
Non alcoholic/non coffee drink	1.67	1.54–1.81	< 0.001
Unflavored	1.31	0.97–1.78	0.079
Other	1.39	1.28–1.52	< 0.001

Table 4.

Logistic regression analysis presenting the odds of each single most often used e-cigarette flavor at the time of quitting smoking for young adults (18–24 years old) compared to older adults (> 24 years old)

	OR	95% CI	P value
Other (reference)
Tobacco	0.52	0.34–0.78	0.002
Menthol	1.58	1.09–2.30	0.016
Mint/wintergreen	1.51	1.00-2.28	0.050
Fruit	1.65	1.16–2.35	0.005
Dessert/pastry/bakery	0.95	0.67–1.36	0.781
Candy/chocolate/sweet	1.08	0.74–1.58	0.677
Spice	0.64	0.38–10.9	0.098
Coffee	0.72	0.46–1.12	0.140
Alcohol/cocktail	0.90	0.45–1.80	0.765
Non alcoholic/non coffee drink	1.83	1.18–2.83	0.007
Unflavored	1.16	0.32–4.26	0.821

The results of the sensitivity analysis comparing age groups 18–24 years with 25–34 years are presented in Table 5 (for e-cigarette flavors used regularly) and 6 (for the single most often used flavor. For flavors used regularly, age group 18–24 years was less likely to use tobacco, dessert/pastry/bakery, candy/chocolate/sweet and spice flavors, and were more likely to use menthol, mint/wintergreen, fruit, coffee non-alcoholic/non-coffee drink and other flavors compared to age group 25–34 years. For the single most often used flavor, age group 18–24 years was more likely to use menthol, Mint/wintergreen and fruit flavors compared to age group 25–34 years, while no statistically significant difference was observed in other flavors.

Table 5.

Logistic regression analysis presenting the odds of regular use of each e-cigarette flavor at the time of quitting smoking for young adults (18–24 years old) compared to adults aged 25–34 years

	OR	95% CI	P value
Tobacco	0.85	0.77–0.95	0.005
Menthol	1.42	1.31–1.53	< 0.001
Mint/wintergreen	1.24	1.13–1.36	< 0.001
Fruit	1.45	1.30–1.60	< 0.001
Dessert/pastry/bakery	0.83	0.77–0.88	< 0.001
Candy/chocolate/sweet	0.93	0.87–0.99	0.021
Spice	0.79	0.71–0.89	< 0.001
Coffee	1.11	1.02–1.21	0.011
Alcohol/cocktail	1.04	0.91–1.19	0.546
Non alcoholic/non coffee drink	1.43	1.31–1.56	< 0.001
Unflavored	1.31	0.95–1.81	0.100
Other	1.26	1.15–1.39	< 0.001

Table 6.

Logistic regression analysis presenting the odds of each single most often used e-cigarette flavor at the time of quitting smoking for young adults (18–24 years old) compared to adults aged 25–34 years

	OR	95% CI	P value
Other (reference)
Tobacco	0.84	0.54–1.32	0.453
Menthol	1.61	1.08–2.42	0.020
Mint/wintergreen	1.49	0.95–2.33	0.081
Fruit	1.52	1.04–2.23	0.030
Dessert/pastry/bakery	0.97	0.66–1.43	0.885
Candy/chocolate/sweet	1.02	0.68–1.53	0.930
Spice	0.99	0.55–1.77	0.968
Coffee	1.00	0.62–1.63	0.987
Alcohol/cocktail	0.98	0.45–2.09	0.947
Non alcoholic/non coffee drink	1.60	1.00-2.55	0.051
Unflavored	1.41	0.33–5.96	0.643

Discussion

To the best of our knowledge, this is the first study that explored the use of e-cigarette flavors specifically at the time of quitting smoking among US young adults aged 18–24 years compared to older adults. While non-tobacco flavors were quite popular in both groups, statistically significant differences were observed between age groups. Younger adults were more likely to use non-tobacco flavors, particularly menthol, mint/wintergreen and fruit flavors, while they were less likely to use tobacco flavors, although the popularity of tobacco flavors was low in both groups. Similar differences were observed in their perception of the importance of different flavors in helping them quit smoking and in avoiding relapse.

Examining the smoking behavior of young adults is important since establishing a long-term smoking habit usually begins in adolescence but extends into early adulthood [17–19]. A substantial proportion of young adults who were smoking or were experimenting with tobacco cigarettes during adolescence are at risk for future smoking [20]. While exploring the value of tobacco harm reduction strategies among young adults who smoke or at risk for smoking appears to be important, most work on e-cigarettes focuses on general patterns of use and on the potential risk for future smoking among those who never smoked in the past. While the literature suggests that younger adults are more likely to consume non-tobacco flavors and to report higher satisfaction from use of such flavors compared to older adults [14, 15, 21–23], limited research exists on the patterns of e-cigarette consumption as a smoking cessation tool. Ramo et al. reported higher prevalence of e-cigarette consumption among young adults who smoke and were more nicotine dependent and interested in quitting [24]. Mantey et al. followed up young adults who currently or formerly smoked for 6 and 12 months and found that those who reported an attempt to quit as a reason for use had higher odds for future cessation [25]. Gagne et al. found that daily e-cigarette consumption was associated with a lower frequency of smoking and more quitting among young adults [26]. Still, the potential influence of different flavors on smoking cessation has not been explored in this age group.

In contrast, there is substantial evidence among adults that non-tobacco e-cigarette flavors play a role in smoking cessation. Population surveys have shown that adult consumers of non-tobacco flavors are more likely to make a quit attempt, reduce smoking consumption and successfully quit compared to those exclusively using non-flavored or tobacco-flavored e-cigarettes [27–30]. Secondary analyses of clinical trials identified that those who consume non-tobacco flavors had higher odds of reducing or quitting smoking [31, 32]. A systematic review of factors associated with the appeal of e-cigarettes among adult smokers concluded that the availability of a variety of flavors is an important parameter that might facilitate complete substitution for cigarettes [33]. Such data raise the need to explore whether similar associations exist among young adults who smoke. However, our study raises another interesting issue, the difference in flavor choices, as well as in perceptions of the importance of different flavors, during the period of smoking cessation between younger and older adults. This could have regulatory implications, since it raises the possibility that non-tobacco flavor preferences among younger adults are not only confined to those who had never smoked but expand to those who smoke, and could potentially facilitate smoking cessation. Thus, any restrictions on flavor variability could compromise the quitting prospects in this age group. It should be noted, however, that non-tobacco flavors are very popular in all age groups, in agreement with other surveys which reported similar findings, particularly for people who have quit smoking [12, 14]. Thus, regulatory restrictions on flavors might compromise cessation attempts among all age groups. Furthermore, the availability of tobacco flavors only represents a choice that most closely resembles the flavor and experience of tobacco cigarettes. It is plausible to hypothesize that maintaining an experience similar to smoking might increase the odds of future relapse, although there is no conclusive evidence for such an effect. Additionally, while flavor restrictions may reduce e-cigarette use, they could simultaneously increase tobacco cigarette use [34–36], particularly among young people [37], as well as result in the creation of an illicit market. Thus, any regulatory decisions should balance the harm reduction prospects of flavor availability in e-cigarettes with the prevention of unintended use by youth and people who do not smoke. Our study provides some insights on the harm reduction prospect of non-tobacco flavors among young adults who smoke, and this should be further explored in longitudinal studies.

It should be mentioned that while observational data suggest that non-tobacco e-cigarette flavors may facilitate smoking cessation, this has not been verified in randomized controlled trials [38]. This may be due to the complex behavioral patterns of use, which was also observed herein since participants reported using several flavors on a regular basis. There is also substantial heterogeneity between different interventional studies, with some providing flavor options at baseline only while other allowing participants to change flavors over time. Similarly, some studies allowed use of flavors bought by the participants themselves, while others asked subjects to use only the flavors provided by the research group [39, 40]. Also, randomization to different flavors may be contaminated by ad libitum use of non-tobacco flavors by those assigned to the tobacco flavor group [41]. Therefore, while randomized controlled studies are necessary to establish causality, there are inherent weaknesses in such a design related to the complex, dynamic and rapidly evolving patters of use and choices among e-cigarette consumers.

An important limitation of the study is the cross-sectional design and the recruitment of a convenience sample of established e-cigarette consumers. Thus, the study was not designed or intended to estimate the population prevalence or frequency of e-cigarette flavor consumption at the time of quitting smoking. It should be, more appropriately, considered as a proof-of-concept analysis that could drive future research focused on the effects of e-cigarette and flavor use among young people who smoke, in addition to never-smoking populations. The large sample size results in small differences being statistically significant. For example, a statistically significant difference in the popularity of tobacco flavors between was observed, and the relative difference in prevalence was 2-fold to 6-fold between groups, but overall use was low in both groups, particularly as the single most often used flavor. Participants in this study had already quit smoking at the time of survey participation and were reporting their flavor use patterns at a time period in the past, raising the possibility for recall bias. The eligibility criteria were relatively permissive regarding the length of smoking abstinence (minimum of 30 days), and participants who had recently stopped smoking would be more likely to relapse compared to those who had quit for longer periods. Such a discrepancy was not addressed in our study. Other characteristics, such as the use higher performance e-cigarette devices or different nicotine concentrations, may also contribute to a successful quit attempt; however, we adjusted our regression analysis to these potential factors. Furthermore, the survey was performed at a time when open systems were the most popular types of e-cigarette devices in the US. While pod systems were already available at that time, over the years the market evolved with increased availability of prefilled and refillable pod systems, as well as an increased use of nicotine salts at high concentrations. Such changes may affect flavor choices and behaviors, which cannot be addressed in this study. While the study provides descriptive data on flavor preferences, it does not explore the underlying reasons why these preferences exist, particularly in relation to smoking cessation. Further qualitative data and expanded questionnaires in future surveys are needed to explore whether the preferential use of some non-tobacco flavors by young adults is due to being more prone to experiment with more flavors or due to psychological, social or cultural factors. One study reported that young adults were more likely to use multiple flavors compared to older adults [15], but did not examine flavor use at the time of quitting cessation. In our study, no difference was found in the number of flavors used regularly between groups. Finally, future studies should longitudinally examine young adults who smoke, and assess how flavor choices affect their smoking cessation attempts and their future smoking status, while the potential differences in flavor choices in different regions outside the US should be explored with similar studies performed locally.

In conclusion, this cross-sectional study of a large sample of US adults who formerly smoked, identified that young adults have different flavor choices at the time of quitting smoking compared to older adults. This information should be further explored in clinical trials using different flavors specifically in younger adults, and should be considered by regulators in order to avoid unintended adverse effects of over-restrictive regulation on e-cigarette flavors.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

KF and CR conceptualized the study; KF, CR, GL and AB prepared the study protocol and questionnaire design; KF, and KP led the data analysis; KF, CR, RP, and GL contributed to the interpretation of the analysis. KF and CR were involved in drafting the initial paper for submission; RP, KP, AB made critical contributions and revisions to the paper; all authors agreed to the final version submitted for publication and agreed to be accountable for all aspects of the work. All authors read and approved the final manuscript.

Funding

No funding was provided for this study.

Data availability

The dataset can become available upon reasonable request.

Declarations

Competing interests

GL, and AB have nothing to report for the past 5 years. CR reports that, in the past three years, his employer, Russell Burnett Research & Consultancy Ltd, has received funding from e‑cigarette/tobacco product manufacturers to conduct behavioral research on population use, use intentions, and perceptions of e‑cigarettes/vaping products, and on the effects of e‑cigarette use/vaping on population use of other tobacco products. KP has received service grants and research funding from a number of Vaping Companies. He is the Head of the Institute of Research and Innovations, which has received a grant from the Foundation for a Smoke Free World. KF has no conflict of interest to report concerning e-cigarettes. Very recently, he has contributed to the development of research protocols for nicotine pouches. RP is full tenured professor of Internal Medicine at the University of Catania (Italy) and Medical Director of the Institute for Internal Medicine and Clinical Immunology at the same University. He has received grants from U-BIOPRED and AIR-PROM, Integral Rheumatology & Immunology Specialists Network (IRIS), Foundation for a Smoke Free World, Pfizer, GlaxoSmithKline, CV Therapeutics, NeuroSearch A/S, Sandoz, Merk Sharp & Dohme, Boehringer Ingelheim, Novartis, Arbi Group Srl., Duska Therapeutics, Forest Laboratories and Ministero dell Universita’ e della Ricerca (MUR) Bando PNRR 3277/2021 (CUP E63C22000900006) and 341/2022 (CUP E63C22002080006), funded by NextGenerationEU, the European Union (EU) economic recovery package. He is founder of the Center for Tobacco Prevention and Treatment (CPCT) at the University of Catania and of the Center of Excellence for the Acceleration of Harm Reduction at the same university. He receives consultancy fees from Pfizer, Boehringer Ingelheim, Duska Therapeutics, Forest Laboratories, CV Therapeutics, and Sermo Inc. He is being paid textbook royalties from Elsevier. He is also involved in a patent application for ECLAT Srl. He is a pro bono scientific advisor for Lega Italiana Anti Fumo (LIAF) and the International Network of Nicotine Consumers Organizations (INNCO); and he is Chair of the European Technical Committee for Standardization on “Requirements and test methods for emissions of electronic cigarettes” (CEN/TC 437; WG4).