Vaping Transitions and Incident Depressive Symptoms among Young Adults: A Marginal Structural Model Analysis.

The extent to which vaping influences depression is unclear, but could be estimated through application of novel epidemiologic methods. Among a prospective cohort of young adults from California who screened negative for depression, we estimated repeated measures marginal structural models to examine the association of four vaping transitions from time T to T+1 (persistent use, discontinuation, initiation, persistent nonuse) with risk of clinically significant depressive symptoms at T+1, simultaneously across three ~1.5 year time-intervals between 2017-2021. Stabilized inverse probability of treatment and censoring weights adjusted for time-dependent confounders and selection bias. Among n=3,496 observations (1,806 participants, mean pooled baseline age=19.5), 8.1% reported persistent vaping from T to T+1, 6.2% reported discontinuation (i.e., use at T and no use at T+1), 6.5% initiated e-cigarettes (i.e., no use at T and use at T+1), and 79.2% reported persistent nonuse at both time-points. Compared to persistent vaping at two waves, persistent nonuse (RR=0.76, 95%CI:0.62-0.93) and discontinuation (RR=0.71, 95%CI:0.52-0.96) were associated with lower risk of depression. Associations were robust to sensitivity analyses, including restricting to tobacco naïve participants and varying temporal assumptions to reduce potential for reverse causation. Young adults who consistently avoid or discontinue vaping may be protected from depressive symptom occurrence.

Longitudinal Transitions Between Use of Combustible, Noncombustible, and Multiple Cannabis Products From Adolescence to Young Adulthood and Intersections With Nicotine Use.

Understanding transitions across use of different types of cannabis products and multiple cannabis products and how they intersect with nicotine use in young people can inform etiology and prevention. In this study, we examined transitions across use of combustible and noncombustible forms of cannabis and multiple types of cannabis from adolescence to young adulthood and the role of nicotine use in transitions. In a Southern California longitudinal cohort study (n = 3,298; baseline mean age = 16.1 (standard deviation, 0.4) years) with 9 semiannual survey waves (2015-2021), we used Markov multistate transition modeling to estimate short-term (2-wave) and long-term (9-wave) probabilities of transition across 5 cannabis use states: never use of any product, prior use with no past-6-month (P6M) use of any product, and P6M use of exclusively noncombustible products, exclusively combustible products, and multiple (noncombustible + combustible) products. Sizable transition probabilities from prior and exclusive P6M noncombustible or combustible cannabis use to P6M poly-cannabis-product use were observed in short-term (10.7%-38.9%) and long-term (43.4%-43.8%) analyses. P6M nicotine use increased risk of transitioning from never and prior use to exclusive P6M noncombustible and combustible cannabis use. Cannabis use in any form, even temporary use, during midadolescence may often be followed by poly-cannabis-product use. Nicotine use may amplify the probability of future cannabis use onset or recurrence.

Recall of Flavor at First E-cigarette Use and its Association with E-cigarette Progression: The Mediating Effects of First Sensory Experience.

OBJECTIVE: To test whether the association between flavor at first vape and continued use is mediated through subjective experience at first vape. STUDY DESIGN: In a 2020 cross-sectional survey, 955 young adult ever-vapers recalled their first flavor vaped, subjective experiences at first use, current vaping behavior, nicotine dependence, and quit attempts. A latent class model grouped first-use subjective experiences into classes. Two-part negative binomial hurdle models for each vaping behavior evaluated whether the association of first flavor used with vaping outcomes was mediated by positive experience. RESULTS: Four latent classes (positive, positive and negative, negative, and minimal experience) were further reduced to "any positive experience" (only positive, positive and negative) vs "no positive experience" (negative or minimal). Class membership mediated the association of first flavor used (mint/menthol/ice [ie, "cooling"] or sweet vs other) with each vaping outcome. For example, cooling flavor (vs. other) was associated with positive class membership (OR=3.5; 95%CI:1.5,8.1), which was then associated with any past 30-day vaping (OR=3.9; 95%CI:2.7,5.8) and greater number of vaping days among current vapers (RR=1.9; 95%CI:1.3,2.7) in the two-part hurdle model. Similar results were observed for nicotine dependence and quit attempts, and for sweet (vs. other) flavor for any dependence or quit attempts, but not number of dependence symptoms or quit attempts. CONCLUSIONS: Use of a cooling or sweet flavor at first use was associated with having a positive first vaping sensory experience, and then greater likelihood as a young adult of reporting past 30-day vaping, more vaping days, and greater risk for nicotine dependence, suggesting a key mediating role of first use experience.

Young Adults' Exposure to and Engagement With Tobacco-Related Social Media Content and Subsequent Tobacco Use.

INTRODUCTION: Nicotine/tobacco social media content may increase young people's risk for use. This study examined prospective associations between exposure to and engagement with nicotine/tobacco-related social media content and nicotine/tobacco use among young adults. AIMS AND METHODS: Young adults (N = 2080) originally recruited from Southern California high schools for a prospective cohort study reported frequency of viewing and posting nicotine/tobacco content on four social media platforms (Facebook, Instagram, Twitter, and YouTube). Participants also reported frequency of seeing nicotine/tobacco posts from friends, seeing nicotine/tobacco posts from influencers or celebrities, and liking nicotine/tobacco posts. Within subsamples of nicotine/tobacco never users (n = 794), past users (n = 897) and current users (n = 389), analyses examined associations of baseline (May-October 2020) social media content exposure and engagement with follow-up (January-June 2021) tobacco use initiation (among never users), resumption (among past users), and continuation (among current users), adjusting for sociodemographic and socioenvironmental characteristics. RESULTS: Never users who saw nicotine/tobacco posts from friends (Adjusted Odds Ratio [AOR] = 2.91 [95% Confidence Interval [CI]: 1.46, 5.82], p = .002) or from celebrities or influencers (AOR = 2.77 [1.32, 5.84], p = .007) were significantly more likely to initiate nicotine/tobacco use than their peers. Among past users, posting nicotine/tobacco content at baseline was associated with use resumption (AOR = 1.77 [1.12, 2.80], p = .014). Content exposure and engagement were not associated with nicotine/tobacco use continuation among current users (p-values > .05). CONCLUSIONS: Seeing nicotine/tobacco posts from friends, influencers, or celebrities was associated with greater odds of tobacco use initiation, but not resumption or continuation, 6 months later. Young adults with past nicotine/tobacco use who post about nicotine/tobacco may be at elevated risk for resuming use. IMPLICATIONS: Young adults with exposure to nicotine/tobacco social media content were more likely than their peers to initiate nicotine/tobacco use 6 months later. Past nicotine/tobacco users who reported posting about nicotine/tobacco on social media at baseline were more likely than their peers to resume nicotine/tobacco use. Among young adults with current nicotine/tobacco use at baseline, social media activity did not predict odds of nicotine/tobacco use continuation at follow-up. Nicotine/tobacco content on social media should be restricted to reduce young people's chances of nicotine/tobacco use initiation or resumption.

Sexual and Gender Identity Disparities in Nicotine and Tobacco Use Susceptibility and Prevalence: Disaggregating Emerging Identities Among Adolescents From California, USA.

INTRODUCTION: Prior studies report nicotine/tobacco use disparities for sexual and gender minority (SGM) youth but have insufficiently characterized SGM identity diversity. AIMS AND METHODS: Adolescents (mean age = 15.2) from 11 high schools in Southern California completed surveys in Fall 2021. Ever use of combustible (cigarettes, cigars, hookah) and noncombustible (e-cigarettes, e-hookah, heated tobacco, smokeless/snus, oral nicotine) nicotine/tobacco (among overall sample, n = 3795) and susceptibility to future initiation of cigarettes, e-cigarettes, and flavored non-tobacco oral nicotine (among n = 3331 tobacco-naïve youth) were compared across four gender (male/masculine, female/feminine, transgender male/female, non-binary) and seven sexual (heterosexual, bisexual, pansexual, queer, questioning, gay/lesbian, asexual) identities. RESULTS: Non-binary (vs. cisgender male) youth had greater prevalence of ever combustible (prevalence ratio [PR] = 2.86, 95% confidence intervals (CI): 1.76 to 4.66) and non-combustible (PR = 1.94, 95% CI: 1.31 to 2.86) nicotine/tobacco use, and susceptibility to future nicotine/tobacco initiation (PR range = 2.32-2.68). Transgender (vs. cisgender male) youth had greater susceptibility to nicotine/tobacco use (PR range = 1.73-1.95), but not greater tobacco use prevalence. There was greater prevalence of non-combustible nicotine/tobacco use (PR range = 1.78-1.97) and susceptibility to nicotine/tobacco initiation (PR range = 1.36-2.18) for all sexual minority (vs. heterosexual) identities, except for asexual. Bisexual (PR = 2.03, 95% CI: 1.30 to 3.16) and queer (PR = 2.87, 95% CI: 1.31 to 6.27) youth had higher ever combustible tobacco use than heterosexual youth. Questioning (vs. heterosexual) youth were more susceptible to future tobacco initiation (PR range = 1.36-2.05) but did not differ in ever use. CONCLUSIONS: Disparities in nicotine/tobacco use and susceptibility were present with similar effect sizes across most, but not all, SGM identities. Inclusive measurement of SGM identities in research and surveillance may inform more precise tobacco control efforts to reduce disparities. IMPLICATIONS: Among high school students from Southern California with substantial diversity in sexual and gender identities, there was greater prevalence of tobacco use and susceptibility to future tobacco initiation for most, but not all, sexual and gender minority youth, including those with emerging sexual and gender identities such as non-binary, queer and pansexual. Additionally, findings indicate that tobacco control initiatives targeting youth who are questioning their sexual identities may be particularly important for preventing tobacco use initiation. This study reinforces the importance of measuring diversity within the LGBTQ + community for tobacco use research, and highlights how inclusive measurement can inform more precise tobacco control interventions.

Effects of exposure to snus marketing with versus without modified risk tobacco product claims on snus use intention and perceived harm among young adults.

BACKGROUND: We tested whether snus marketing with modified risk tobacco product (MRTP) claims: (a) promotes accurate knowledge about snus's health effects in young adults and (b) encourages use intentions in only those who use combustible tobacco without attracting other young adult populations. METHODS: A randomised between-subjects experiment was embedded in a 2020 web survey of participants from Los Angeles (aged 19-23 years). Participants viewed mass-marketed snus advertising materials with (n=1212) vs without (n=1225) US Food and Drug Administration-authorised MRTP claims. After advertising exposure, snus use intention and perceptions of snus harms relative to cigarettes or e-cigarettes were measured. RESULTS: Advertisements with versus without MRTP claims did not affect snus use intention (18.0% vs 19.4%) but produced a higher prevalence of perceptions that snus was less harmful than cigarettes (12.6% vs 9.1%; p=0.007) and e-cigarettes (8.0% vs 5.8%; p=0.04). MRTP claim exposure effects did not differ by past 30-day e-cigarette or combustible tobacco use. Snus use intentions after marketing exposure, collapsed across MRTP claim conditions, were higher in those who did versus did not report past 30-day use of e-cigarettes (38.4% vs 14.3%; adjusted OR (95% CI) 2.95 (2.28 to 3.81); p<0.001) or combustible tobacco (44.0% vs 16.2%; adjusted OR (95% CI) 2.26 (1.62 to 3.16); p<0.001). CONCLUSION: Although some young adults who vape or smoke may have snus use intentions, snus MRTP claims might not affect young adults' snus use intentions, regardless of whether they vape/smoke. MRTP claims might modestly increase the accuracy of perceived harms of snus relative to cigarettes while also slightly causing unsubstantiated perceptions of lower harm than e-cigarettes.

Importance of Various E-Cigarette Device and E-Liquid Characteristics by Smoking Status among Young Adults Who Vape.

BACKGROUND: E-cigarette product characteristics are known to influence appeal among young adults. Understanding which characteristics appeal to individuals with (vs. without) a history of combusted tobacco use is essential for developing effective tobacco control policies. METHODS: Anonymous, self-report data were collected from young adults (18-30 years) who had used e-cigarettes in the past 30 days (n = 295) online via Prolific from September-October 2019. Using a visual analogue scale (range: 0-100), participants rated the importance of ten e-cigarette device and nine e-liquid characteristics. Adjusted linear regression models were used to evaluate the association of combusted tobacco use status (never, former, current) with mean rating scores for each of the nineteen characteristics. RESULTS: The most important e-cigarette device characteristics were price (Mean = 81.1; [SD = 17.9]), size (Mean = 75.5 [SD = 20.9]), and hit strength (Mean = 73.8 [SD = 20.4]) while the most important e-liquid characteristics were flavor (M = 85.1 [SD = 16.3]), price (M = 80.9 [SD = 18.4]), and nicotine level (M = 77.8 [18.9]). Differences by combusted tobacco use status were observed for device brand, temperature/voltage, customizability, color, and popularity, with the highest ratings generally observed among those concurrently using combustible tobacco products. For e-liquids, differences by use status were observed for flavor, price, and bottle type. Notably, those concurrently using combusted products rated flavor as less important than those with no history of combustible tobacco use (B=-5.01[95%CI=-9.97, -0.05]). CONCLUSIONS: The self-rated importance of e-cigarette device and e-liquid attributes varies by combustible tobacco use status among young adults which may be used to inform regulatory decisions regarding e-cigarette product characteristics.

Alcohol Use and Life Stressors During the COVID-19 Pandemic: A Longitudinal Study of Young Adults.

Objective: To estimate the extent to which drinking to cope with the COVID-19 pandemic and experiencing pandemic-related life stressors are associated with alcohol use escalation among young adults. Methods: Respondents in Los Angeles, CA, USA (N=2,130) completed prospective cohort study surveys before (baseline; October 2018-November 2019; mean age: 19.7[SD=0.4) and during (follow-up; May-August 2020) the COVID-19 outbreak. Past 30-day drinking days and number of drinks per drinking day were assessed from baseline to follow-up. At follow-up, participants reported drinking to cope with social isolation and pandemic-related stressors. Results: Pandemic-related stressor prevalence ranged from 5.5% (evicted/lost home) to 72.6% (worried about education) and 27.1% drank to cope with social isolation during the pandemic. Respondents who did (vs. did not) report pandemic-related coping drinking were more likely to increase past 30-day drinking days and drinks per drinking day from baseline to follow-up after adjustment for possible confounders. Employment loss/reduction, financial problems, and perceived likelihood of contracting COVID-19 or handling the pandemic poorly were each associated with increases in drinking days or drinks per drinking day. Conclusions: Experiencing certain life stressors and drinking to cope with social isolation may be associated with drinking escalation among young adults during the COVID-19 pandemic.

Prevalence of and disparities in adolescents' susceptibility to novel oral nicotine products marketed as "tobacco-free".

Non-therapeutic, novel oral nicotine products are convenient, discreet to use, and flavored, with increasing sales in the United States. It is unclear whether these products appeal predominantly to adolescents already susceptible to inhalable nicotine products, or whether they attract adolescents who would not otherwise use nicotine. This study examined prevalence and correlates of susceptibility to inhalable and oral nicotine product use among adolescents. Ninth- and tenth-grade students from Southern California who had never used any nicotine product (N = 3129) completed an online survey in Fall 2021 assessing susceptibility to inhalable (i.e., cigarettes, e-cigarettes) and oral (e.g., pouches, gum, gummies) nicotine products. Multinomial logistic regression analyses estimated associations of demographic characteristics with odds of susceptibility to oral, inhalable, or both products. Susceptibility was highest for e-cigarettes (19.7%), followed by cigarettes (15.0%) and nicotine gum, lozenges, tablets and/or gummies (15.0%), and nicotine pouches (8.7%). Dual susceptibility to oral and inhalable products (vs. neither product type) was higher in cisgender female and non-cisgender (vs. cisgender male) adolescents (odds ratios [ORs] = 1.36-2.02; ps < 0.05). Hispanic adolescents (vs. Asian) were more susceptible to both products (OR = 1.47; p < .05). Lower-socioeconomic status (SES) and sexual minority adolescents were more susceptible to oral (ORs = 1.76-1.87; ps < 0.05) and both products (ORs = 1.32-1.88; ps < 0.05), compared to higher-SES and heterosexual adolescents. Adolescents in Southern California may be more susceptible to e-cigarettes than other nicotine/tobacco products. However, appreciable numbers may be susceptible to oral nicotine products, including some youth who might not otherwise use nicotine and youth from populations historically impacted by tobacco-related health disparities.

Differentiating Reasons for Young Adult E-cigarette Use Using Maximum Difference Choice Models.

INTRODUCTION: Understanding the reasons young adults use e-cigarettes (ie, vape)-and whether these motivations vary across groups-is essential for informing tobacco regulatory efforts. AIMS AND METHODS: An online panel of young adults who vape (n = 230; age = 18-30 years) completed a maximum difference discrete choice task for 15 reasons for vaping. Over 9 choice sets, participants were presented a subset of 5 reasons and selected the most and least important. Hierarchical bayesian analysis estimated the relative importance of each reason. Latent class analysis (LCA) identified groups with similarly ranked reasons for use. Multinomial regression evaluated the association between sample characteristics and class membership. RESULTS: Overall, relaxation had the highest probability of being the most important reason for use (14.8%), followed by harm reduction (13.2%), and flavors (10.3%). LCA identified five distinct classes, based on top reasons for use: 1. cessation (cigarette cessation [20.2%]; n = 80); 2. dependence (relaxation [20.5%] and unable to quit [19.2%]; n = 21); 3. relaxation (relaxation [20.6%]; n = 66); 4. socializing (socializing [22.2%]; n = 27); and 5. variable (boredom [10.5%] and acceptability [10.2%]; n = 36). Participants who were older, smoked cigarettes, or vaped more frequently were more likely to belong to the cessation class while those who were younger or more e-cigarette dependent were more likely to belong to the dependence class. CONCLUSIONS: Perceived reasons why young adults vape are highly heterogeneous and dependent on the type of user. Tobacco regulatory efforts targeting distinct types of vapers are needed to minimize the adverse public health impact of vaping without compromising appeal for smoking cessation. IMPLICATIONS: E-cigarette use remains high among young adults, with flavors, cost, and harm reduction (vs. combustible cigarettes) among the mostly commonly reported reasons for use. Yet, little is known about how relatively important these reasons are to the individual. Leveraging a maximum difference task, young adults' reasons for use were evaluated on a common interval scale and groups sharing similar reasons identified. Smoking cessation, dependence, relaxation, socialization, and boredom were respectively the most important reasons for use among five classes of vapers. E-cigarette regulatory policies should consider the distinct reasons for use as to not compromise their appeal for smoking cessation.

E-cigarette Device Type, Source, and Use Behaviors of Youth and Young Adults: Findings from the Truth Longitudinal Cohort (2020-2021).

Background: E-cigarette device types vary in the amount of nicotine delivered to users. Given that youth and young adults are using pod-based and disposable e-cigarettes with high nicotine concentrations, it is important to determine how e-cigarette use behaviors associated with nicotine dependence may differ across e-cigarette device type. Methods: Baseline information was collected from September 2020 to March 2021 and follow-up information was collected from July to October 2021 from the Truth Longitudinal Cohort. The final analytic sample included respondents (aged 15-24) who reported current use of e-cigarettes at either baseline or follow-up and provided information on the 4-item E-cigarette Dependence Scale (EDS). Differences in endorsement of items from the EDS by e-cigarette device type (pod-based, disposable, or tank) were assessed using chi-square tests. Results: Participants (N = 308) were evenly split on age (15-20, 21+) and gender. Most 15-20-year-olds used disposable e-cigarettes, while those 21+ years primarily used tank devices. Although EDS score did not differ by e-cigarette device type, positive endorsement of two items from the EDS significantly differed by e-cigarette device type. More tank users endorsed reaching for a device without thinking about it (tank: 92.6%; pod-based: 79.0%; disposables: 79.9%, p = 0.04) and vaping more before going into a situation where vaping is not allowed (tank: 92.9%; pod-based: 71.0%; disposables: 73.0%, p < 0.01). Conclusions: Findings have the potential to inform policy implementation by providing evidence for specific targets for regulatory action that can help to reduce the burdens of e-cigarette use among youth and young adults, as results suggest that tank device users are more likely to endorse use behaviors associated with nicotine dependence.

e-Cigarette Use and Combustible Cigarette Smoking Initiation Among Youth: Accounting for Time-Varying Exposure and Time-Dependent Confounding.

BACKGROUND: Youth e-cigarette use is associated with the initiation of combustible cigarette smoking, but prior studies have rarely accounted for time-varying measures of e-cigarette exposure or time-dependent confounding of e-cigarette use and smoking initiation. METHODS: Using five waves of the Population Assessment of Tobacco and Health (2013-2019), we estimated marginal structural models with inverse probability of treatment and censoring weights to examine the association between time-varying e-cigarette initiation and subsequent cigarette smoking initiation among e-cigarette- and cigarette-naïve youth (12-17 years) at baseline. Time-dependent confounders used as predictors in inverse probability weights included tobacco-related attitudes or beliefs, mental health symptoms, substance use, and tobacco-marketing exposure. RESULTS: Among 9,584 youth at baseline, those who initiated e-cigarettes were 2.4 times as likely to subsequently initiate cigarette smoking as youth who did not initiate e-cigarettes (risk ratio = 2.4, 95% confidence interval [CI] = 2.1, 2.7), after accounting for time-dependent confounding and selection bias. Among youth who initiated e-cigarettes, more frequent vaping was associated with greater risk of smoking initiation (risk ratio ≥3 days/month = 1.8, 95% CI = 1.4, 2.2; 1-2 days/month = 1.2; 95% CI = 0.93, 1.6 vs. 0 days/month). Weighted marginal structural model estimates were moderately attenuated compared with unweighted estimates adjusted for baseline-only confounders. At the US population level, we estimated over half a million youth initiated cigarette smoking because of prior e-cigarette use over follow-up. CONCLUSIONS: The association between youth vaping and combustible cigarette smoking persisted after accounting for time-dependent confounding. We estimate that e-cigarette use accounts for a considerable share of cigarette initiation among US youth. See video abstract at, http://links.lww.com/EDE/B937.

Patterns and mediators of racial and ethnic disparities in COVID-19 vaccine hesitancy among young adults.

COVID-19 vaccines have been available for over a year, yet 26% of U.S. young adults remain unvaccinated. This study examines racial and ethnic disparities in young adult vaccine hesitancy and attitudes/beliefs that mediate disparities in vaccine hesitancy. Young adults (n = 2041;Mean[SD]:21.3[0.7] years-old) from a Los Angeles, CA, USA cohort were surveyed online in January-May 2021 and classified as vaccine hesitant (those who reported "Not at all likely"/"Not very likely" /"Slightly likely" to get vaccinated) versus non-hesitant (those who reported "Moderately likely"/"Very likely"/"Definitely likely" to get vaccinated or already vaccinated). Multivariable logistic regression was performed to examine racial/ethnic disparities in vaccine hesitancy. Factor analysis was conducted to create three subscales toward vaccination: positive, negative, and lack-of-access beliefs. Mediation analyses were performed to assess pathways from attitude/belief subscales to racial disparities in vaccine hesitancy. Overall 33.0% of respondents reported vaccine hesitancy. Black vs. White young adults had a higher prevalence of vaccine hesitancy (AOR[95%CI] = 4.3[2.4-7.8]), and Asians vs. Whites had a lower prevalence (AOR[95%CI] = 0.5[0.3-0.8]). Mediators explained 90% of the Black (vs. White) disparity in vaccine hesitancy, including significant indirect effects through positive belief-reducing (ß = 0.23,p < .001) and negative belief-enhancing (ß = 0.02,p = .04) effects. About 81% of the Asian (vs. White) disparity in vaccine hesitancy was explained by the three combined subscales, including significant positive belief-reducing (ß = -0.18,p < .001) indirect effect. Substantial racial and ethnic disparities in young adult COVID-19 vaccine hesitancy were found, which were mediated by differences in attitudes and beliefs toward vaccination. Targeted education campaigns and messages are needed to promote equitable utilization of the effective vaccine.

Modeling the longitudinal transitions of electronic cigarettes and conventional cigarettes with time-dependent covariates among adolescents.

E-cigarettes may help combustible cigarette smokers switch to a less harmful alternative, or may increase the risk of subsequent initiation of cigarettes among non-smokers. Among youth, it is not clear whether both pathways occur equally, or whether one direction is more likely than the other. We used data from a prospective cohort study of youth in Southern California followed twice annually from Fall 2013 (9th grade) to Fall 2015 (11th grade) (N = 1977). A polytomous logistic regression model was used to simultaneously estimate transition rates for initiation of and abstention from e-cigarettes and cigarettes. Use of e-cigarettes was positively associated with initiation of cigarettes (OR = 7.57; 95%CI:[5.32, 10.8]) and negatively associated with cigarette abstention (OR = 0.58; 95%CI:[0.33, 0.99]) in adjusted models; cigarette use was positively associated with e-cigarette initiation (OR = 2.54; 95%CI:[1.45, 4.47]) and negatively associated with e-cigarette abstention (OR = 0.31; 95%CI:[0.17,0.57]). Uni-directional transition from e-cigarettes only to cigarettes only occurred less frequently than expected under independence (OR = 0.33; 95% CI [0.20, 0.55]), whereas simultaneously initiating both products (OR = 9.79; 95%CI:[7.22, 13.3]) and simultaneously abstaining (OR = 2.84; 95%CI:[1.50, 5.37]) were more frequent than expected. E-cigarettes were more strongly associated with subsequent cigarette initiation than the reverse, though both models indicated that use of either product seems to encourage use of the other. Models also indicated that use of either e-cigarettes or cigarettes resulted in reduced abstention of the other product. Findings suggest that prevention efforts for that continue to focus on both e-cigarettes and cigarettes are needed.

Longitudinal associations between flavored tobacco use and tobacco product cessation in a national sample of adults.

Use of flavored tobacco has been associated with lower likelihood of short-term abstinence from tobacco. It is unknown whether longer-term associations exist, particularly for a variety of products and specific flavor categories. This study used adult survey data from the Population Assessment of Tobacco and Health (PATH) Study (2013-2018). We tested associations of past 30-day tobacco product use at wave 2 using both a 2-category any flavor versus unflavored variable and 4-category specific flavor (menthol/mint, sweet, and both menthol/mint and sweet) versus unflavored variable with past 12-month cessation from the same product two years later at wave 4. Separate models were run for each product (combustible cigarettes, cigars, hookah, e-cigarettes, and smokeless), adjusting for wave 1 sociodemographic characteristics. For all five products, past 30-day use of any flavored (versus unflavored) product at wave 2 was associated with reduced likelihood of same-product cessation at wave 4. Most specific flavor categories were associated with reduced odds of same-product cessation across all products. Any flavor use was also associated with reduced likelihood of longer-term cessation (i.e., past 24-months at both waves 3 and 4) and cessation from all five tobacco products in several analyses. Exploratory moderation results indicated that the association between e-cigarette flavor use and lower likelihood of cessation was stronger for young adults (18-24) versus older adults (25+). Current use of flavored tobacco products is associated with lower likelihood of product cessation. Flavored tobacco products warrant consideration in regulatory policy to reduce the adverse public health impact of tobacco use.

A Machine Learning Approach to Identify Predictors of Frequent Vaping and Vulnerable Californian Youth Subgroups.

INTRODUCTION: Machine learning presents a unique opportunity to improve electronic cigarette (vaping) monitoring in youth. Here we built a random forest model to predict frequent vaping status among Californian youth and to identify contributing factors and vulnerable populations. METHODS: In this prospective cohort study, 1281 ever-vaping twelfth-grade students from metropolitan Los Angeles were surveyed in Fall and in 6-month in Spring. Frequent vaping was measured at the 6-month follow-up as nicotine-containing vaping on 20 or more days in past 30 days. Predictors (n = 131) encompassed sociodemographic characteristics, substance use and perceptions, health status, and characteristics of the household, school, and neighborhood. A random forest was developed to identify the top ten predictors of frequent vaping and interactions by sociodemographic variables. RESULTS: Forty participants (3.1%) reported frequent vaping at the follow-up. The random forest outperformed a logistic regression model in prediction (C-Index = 0.87 vs. 0.77). Higher past-month nicotine concentration in vape, more daily vaping sessions, and greater nicotine dependence were the top three of the ten most important predictors of frequent vaping. Interactions were found between age and perceived discrimination, and between age and race/ethnicity, as those who were younger than their classmates and either reported experiencing discrimination frequently or identified as Asian or Native American/Pacific Islander were at increased risk of becoming frequent vapers. CONCLUSIONS: Machine learning can produce models that accurately predict progression of vaping behaviors among youth. The potential association between frequent vaping and perceived discrimination warrants more in-depth analyses to confirm if discrimination constitutes a cause of increased vaping. IMPLICATIONS: This study demonstrates the utility of machine learning in predicting status of frequent vaping over 6 months and understanding predictors and nuanced intersectionality by sociodemographic attributes. The high performance of the random forest model has practical implications for a personalized risk calculator that supports vaping prevention program. Public health officials need to recognize the importance of social factors that contribute to frequent vaping, particularly perceived discrimination. Youth subpopulations, including younger high school students and Asians or Native Americans/Pacific Islanders, might require specially designed interventions to help prevent habit-forming in vaping.

Critical Challenges and Creative Solutions for Quantifying Nicotine Vaping: Qualitative Reports From Young Adults.

INTRODUCTION: Previous studies suggest that young adults who vape nicotine experience difficulty when answering survey items assessing the quantity of vaping. The current study asked young adults who vape to provide suggestions for improving the scientific measurement of vaping. AIMS AND METHODS: We conducted semi-structured qualitative interviews with 62 young adults who vape in Los Angeles, California between June 2018 and June 2019. We analyzed participants' responses to the following question: "What do you think is the best way for us to understand how much people vape?" using thematic content analysis. RESULTS: We identified two major themes: (1) challenges stemming from differences between the way researchers query about vaping and how individuals self-monitor vaping frequency, and (2) insights for future measurement of vaping. Participants reported that challenges of accurately quantifying vaping were due to inherently hard-to-answer questions (eg, puffs per day), lack of awareness of or not actively monitoring consumption of vaping products, or because vaping behaviors vary considerably between and within individuals over time, making "on-average" questions challenging. Participants discussed ideas for improving survey measures that could accurately assess vaping quantity, including querying about the type of device used, and frequency of replenishment of nicotine solutions. CONCLUSIONS: Existing vaping behavior survey measures may not accurately capture the quantity of vaping as they differ from how (or if) participants track their own vaping consumption patterns. While continued research is needed to optimally refine survey measures on vaping consumption, future measures may better align with vapers' self-monitoring by including questions on device-type and replenishment frequency. IMPLICATIONS: The present study provides insights regarding the variability that exists between vaping quantity measurements utilized by researchers and individuals who consume e-cigarettes. The qualitative data analyzed for this study support previous reports of difficulties faced by vapers when asked questions by researchers related to their vaping behavior. Furthermore, the present findings suggest the direction for the future development of accurate measurements of vaping frequency.

Disposable E-Cigarette Use Prevalence, Correlates, and Associations With Previous Tobacco Product Use in Young Adults.

INTRODUCTION: Novel, inexpensive disposable e-cigarettes widely sold in attractive flavors might be exempt from US federal regulations. To inform regulatory and public health priorities, this study examined young adult disposable e-cigarette use uptake among existing tobacco users versus non-users and possible use correlates that could be potential regulatory targets. AIMS AND METHODS: Prospective cohort data were analyzed in 2021. Among baseline (2018-2019) never disposable e-cigarette users (n = 1903; mean [SD]: 19.3 [0.8] years-old), we tested prospective associations of baseline tobacco product use with follow-up (2020) disposable e-cigarette use initiation, followed by stratified analyses distinguishing baseline exclusive and dual e-cigarette/combustible tobacco use. Exploratory cross-sectional associations of tobacco-related correlate with vaping frequency among current disposable users (n = 266) were tested. RESULTS: Follow-up ever disposable e-cigarette use initiation was higher among baseline former (22.1%) and current (50.2%) versus never (6.3%) rechargeable (non-disposable) e-cigarette users. In stratified analyses, follow-up disposable e-cigarette use initiation was 0% in baseline never-vaping exclusive current smokers, higher in baseline never-vaping former smokers versus never users of any tobacco product (18.2% vs. 5.7%; adjusted odds ratio [95% CI] = 3.9 [2.1-7.5]), and higher among baseline current dual users versus never-smoking exclusive current vapers (61.3% vs. 42.2%; adjusted odds ratio [95% CI] = 3.0 [1.5-6.0]). Among follow-up current disposable e-cigarette users (overall prevalence = 10.9%), using ice-flavored (vs. fruit/sweet-flavored) e-cigarettes (adjusted rate ratio [95% CI] = 1.5 [1.0-2.1]) and vaping dependence symptoms (adjusted rate ratio [95% CI] = 2.2 [1.5-3.2]) were cross-sectionally associated with more past-month disposable e-cigarette use days. CONCLUSIONS: Young adult disposable e-cigarette use was of appreciable prevalence, including among tobacco product never users and former smokers. Regulation of disposable e-cigarettes, including ice-flavored products, might benefit young adult health. IMPLICATIONS: Sales of disposable e-cigarette products increased significantly in the United States from 2019 to 2020. These products contain high nicotine concentrations and various flavors that may appeal to young people. This study provides the first evidence that disposable e-cigarette use may be common among young adults, including among tobacco product never users and former smokers. Frequency of disposable e-cigarette use was positively associated with using ice-flavored e-cigarettes and vaping dependence. Regulatory policies and enforcement strategies addressing disposable e-cigarettes merit consideration in young adult health policy and prevention priorities.

First E-Cigarette Flavor and Device Type Used: Associations With Vaping Persistence, Frequency, and Dependence in Young Adults.

INTRODUCTION: Type of e-cigarette flavoring and device during first use might differentiate later e-cigarette use and dependence. This retrospective cross-sectional study examined associations of recalled first nicotine vaping device and flavor used with current vaping frequency/dependence. AIMS AND METHODS: A young adult cohort from Los Angeles, California, USA completed web-based surveys (N = 2553). Using cross-sectional data from 971 reporting ever vaping nicotine, multivariable hurdle regressions tested associations between recalled first flavor (fruit/sweet, menthol/mint, other) and device (Juul, disposable, mod, box, pod, pen, other) vaped with past-30-day vaping status (yes/no) and frequency (1-30 days), and with any vaping dependence symptoms (yes/no) and count (1-10 symptoms). RESULTS: The most common first-flavor was sweet (71%); the most common first-device was a vape pen (37%), then Juul (22%). First-flavor of mint/menthol (vs. other; adjusted odds ratio [AOR]: 2.22[95% CI = 1.16 to 4.25]), and first-device mod (AOR = 2.40[95% CI = 1.34 to 4.31]) and non-Juul pod (2.64[95% CI = 1.41 to 4.92]) (vs. pen) were associated with past-30-day vaping, and twice as many vaping days (adjusted rate ratios [ARRs] range: 1.96-2.12; ps < .05). First flavor of mint/menthol (vs. other; AOR: 1.95[95% CI = 1.003 to 3.79) and first device mod, box, non-Juul pod, and other (AORs range: 2.36-4.01; ps < .05) were associated with nicotine dependence. First device Juul, mod, box, and non-Juul pod were also associated with more dependence symptoms (ARRs range:1.38-1.59; ps < .05). CONCLUSIONS: Exposure to mint/menthol and certain devices (mod, box, Juul, and non-Juul pods) at first e-cigarette use may be associated with more frequent e-cigarette use and nicotine dependence symptoms in young adulthood. Mint/menthol and certain devices warrant consideration in regulation of e-cigarettes based on product characteristics. IMPLICATIONS: Characteristics (flavor and device type) of first e-cigarette product used were associated with higher usage and more dependence. Pending replication with prospective designs, the findings suggest certain flavors (mint/menthol) and devices (pods, mods) merit consideration in regulation because of their possible link with continued use and dependence among young people.

Trajectories of Nicotine Use Leading to Dual and Cyclical Tobacco Product Use in Young Adults.

INTRODUCTION: Young adult never-smokers who vape are at elevated risk of initiating cigarettes, while young adults who smoke often begin vaping to substitute or reduce cigarette use. Reasons underlying different use patterns of tobacco products are not well-understood. AIMS AND METHODS: We conducted 1-on-1 qualitative interviews with young adults (N = 62) who vape in Los Angeles, California from June 2018 to June 2019. Participants were 18-25 years old (79% male; racially/ethnically diverse) and self-reported vaping ≥1x/week. We used a semi-structured interview guide and applied thematic analysis method to analyze data. RESULTS: Young adults initiated vaping due to peer socialization and e-liquid flavor novelty. They often reported vaping (after first smoking) due to a belief that e-cigarettes are healthier, social pressure to quit smoking, and convenience of use. Participants reported smoking (after first vaping) when traveling outside of the United States where vaping products were less accessible, and cigarettes were normative. Many of the personal narratives described patterns of dual and cyclical use, which was often attributed to nicotine dependence and cost, or described as dependent upon the current environment (eg, at a party). CONCLUSIONS: The current study characterizes nicotine use trajectories and reasons why young adults vape, and smoke cigarettes. Dual and cyclical use of both e-cigarettes and cigarettes was common; this pattern of use should be considered in policy and prevention work to address nicotine dependence among young people. IMPLICATIONS: We display findings from the current study in a model depicting common trajectories of nicotine use, along with reasons for initiation, transitions between products, and dual/cyclical e-cigarette and combustible cigarette use.