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.

Prospective study of e-cigarette use and respiratory symptoms in adolescents and young adults.

RATIONALE: Electronic cigarette (e-cigarette) aerosol contains volatile aldehydes, including flavourings and oxidant metals with known pulmonary toxicity. OBJECTIVES: To evaluate the associations of e-cigarette use with symptoms of wheeze, bronchitic symptoms and shortness of breath (SOB) across 4 years of prospective data. METHODS: Participants completed questionnaires on respiratory symptoms and past 30-day e-cigarette, cigarette and cannabis use in 2014 (wave 1; N=2094; mean age 17.3 years, SD=0.6 years). Follow-up information was collected in 2015 (wave 2; n=1609), 2017 (wave 3; n=1502) and 2018 (wave 4; n=1637) using online surveys. Mixed-effects logistic regression models evaluated associations of e-cigarette use with respiratory symptoms. MEASUREMENTS AND MAIN RESULTS: Participants were mostly Hispanic white (51.8%) and evenly representative by sex (49.6% female; 50.4% male). Compared with never e-cigarette users, past 30-day e-cigarette users reported increased odds of wheeze (OR 1.81; 95% CI 1.28, 2.56), bronchitic symptoms (OR 2.06; 95% CI 1.58, 2.69) and SOB (OR 1.78; 95% CI 1.23, 2.57), adjusting for study wave, age, sex, race, lifetime asthma diagnosis and parental education. Effect estimates were attenuated (wheeze (OR 1.41; 95% CI 0.99, 2.01), bronchitic symptoms (OR 1.55; 95% CI 1.18, 2.05), SOB (OR 1.48; 95% CI 1.01, 2.18)), after adjusting additionally for current cigarette use, cannabis use and secondhand exposure to e-cigarettes/cigarettes/cannabis. CONCLUSIONS: E-cigarette use in young adults was associated with respiratory symptoms, independent of combustible cannabis and cigarette exposures.

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.

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.

Characterizing Opioid Withdrawal Experiences and Consequences Among a Community Sample of People Who Use Opioids.

BACKGROUND: Opioid withdrawal symptoms are a highly salient and consequential health condition experienced by people who use opioids (PWUO). This study utilized qualitative interviews to explore opioid withdrawal experiences and consequences among PWUO in Los Angeles County, USA. METHODS: Semi-structured qualitative interviews were conducted with 22 PWUO (aged 27-63 years) between May 2021 and May 2022. Participants self-reported opioid and injection drug use in the last 30 days. We employed an inductive thematic approach to systematically code and synthesize textual interview data. RESULTS: Participants experienced withdrawal symptoms frequently, with many going to great lengths to avoid them. Withdrawal pain was described as incapacitating and interfered with PWUO's ability to sustain regular employment and ensure stable housing. Avoiding withdrawal was described as influential in driving decisions to continue using opioids. Mechanisms for managing withdrawal included using other substances to the point of sedation. PWUO who transitioned from heroin to fentanyl use revealed more frequent, painful, and faster onset of withdrawal symptoms. Adverse withdrawal experiences and fear of precipitated withdrawal from buprenorphine were barriers to treatment initiation and continuation. CONCLUSION: Withdrawal symptoms among PWUO increase health risk. Improved strategies to treat opioid withdrawal are urgently needed. Solutions such as safe supply and intentional opioid withdrawal interventions (educational trainings, withdrawal comfort kits) are needed to improve withdrawal management and reduce opioid-related harm.

Re: Impact of the "e-cigarette era" on cigarette smoking among youth: A population-level study.

Our original paper is: Harrell MB, Mantey DS, Baojiang C, Kelder SH, Barrington-Trimis J. Impact of the e-cigarette era on cigarette smoking among youth in the United States A population-level study. Preventive Medicine 2022; 164:107265). This is a response to correspondence received from Foxon and Juul Labs Inc. (JUUL) regarding our original paper.

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.

'Ice' flavoured e-cigarette use among young adults.

BACKGROUND: 'Ice' e-cigarette flavours-marketed as a combination of fruity/sweet and cooling flavours (eg, 'blueberry ice' or 'melon ice')-recently entered the US market. The prevalence and correlates of ice flavoured e-cigarette use in young adults are unknown. METHODS: This cross-sectional study of a Los Angeles, California, USA, cohort analysed data from the past 30-day e-cigarette (current) users (n=344; M (SD)=21.2 (0.4) years old) who completed web-based surveys from May-August 2020. The exposure variable was self-reported e-cigarette flavour used most often in the past month (menthol/mint, fruit/sweet or ice). Outcomes included self-reported combustible tobacco use, vaping dependence symptoms, frequency of use and device type used. RESULTS: Among current e-cigarette users, 48.8% reported using ice flavours most often, 33.7% predominately used fruit/sweet and 17.4% used menthol/mint. Using primarily ice-flavour was associated with reporting more past-30-day vaping days (vs menthol/mint: b=4.4, 95% CI (1 to 7.7); vs fruit/sweet: b=3.6, 95% CI (0.8 to 6.4)) and more episodes per vaping day versus fruit/sweet users (b=2.4, 95% CI (0.5 to 4.3)). Ice-flavour users were less likely than menthol/mint users to use JUUL/cartridge-based rechargeable (OR=0.1, 95% CI (0.03 to 0.45)) and more likely than sweet/fruit users to use disposable non-cartridge (OR=3.9, 95% CI (2.1 to 7.4)) devices than refillable/rechargeable tank/pen or other devices. Ice users had greater odds of past 30-day combustible tobacco use versus menthol/mint users (OR=2.7, 95% CI (1.3 to 5.7)) and vaping dependence symptoms than versus sweet/fruit users (OR=2.6, 95% CI (1.5 to 4.4)). CONCLUSION: Young adult use of ice flavoured e-cigarettes may be common and positively associated with combustible tobacco use, nicotine vaping frequency and dependence and use of disposable e-cigarette devices. Further study of the prevalence, determinants and health effects of ice flavoured e-cigarette use is warranted.

Effects of dual use of e-cigarette and cannabis during adolescence on cigarette use in young adulthood.

INTRODUCTION: E-cigarette and cannabis use by adolescents are risk factors for smoking initiation. We hypothesised that increasingly common dual use of e-cigarette and cannabis in adolescence leads to more frequent cigarette smoking in young adulthood. METHODS: Data are from a prospective cohort study in Southern California, where 1164 participants who ever used nicotine products in their lifetime completed surveys in 12th grade (T1:2016), and at 24-month (T2) and 42-month (T3) follow-ups. Past 30-day use (number of days: range=0-30) of cigarettes, e-cigarettes and cannabis, and nicotine dependence, were assessed in each survey. Nicotine dependence for cigarettes and e-cigarettes was assessed using original and modified (for e-cigarette) Hooked on Nicotine Checklists (number of dependent products: range=0-2). Path analysis examined the mediation process via nicotine dependence linking baseline e-cigarette and cannabis use to subsequent increased cigarette use. RESULTS: Baseline exclusive use of e-cigarettes (baseline prevalence, 2.5%) was associated with 2.61-fold increase in frequency of smoking days at T3 (95% CI 1.04 to 13.1), exclusive cannabis use (26.0%) with 2.58-fold increase (95% CI 1.43 to 4.98), and dual use (7.4%) with 5.84-fold increase (95% CI 3.16 to 12.81), compared with baseline non-users. Nicotine dependence at T2 mediated 10.5% (95% CI 6.3 to 14.7) and 23.2% (95% CI 9.6 to 36.3) of the association of cannabis and dual use, respectively, with increased smoking at T3. DISCUSSION: Adolescent e-cigarette and cannabis use was associated with more frequent smoking during young adulthood, with larger effects of dual use. Associations were partially mediated through nicotine dependence. Dual use of cannabis and e-cigarettes may contribute to the development of nicotine dependence and increased use of combustible cigarettes.

Effect of a hypothetical modified risk tobacco product claim on heated tobacco product use intention and perceptions in young adults.

INTRODUCTION: Modified risk tobacco product (MRTP) claims for heated tobacco products (HTPs) that convey reduced exposure compared with conventional cigarettes may promote product initiation and transition among young people. We assessed the effects of a hypothetical MRTP claim for HTPs on young adults' intention and perceptions of using HTPs and whether these effects differed by their current cigarette and e-cigarette use. METHODS: We embedded a randomised between-subjects experiment into a web-based survey administered among a cohort of 2354 Southern California young adults (aged 20-23) in 2020. Participants viewed depictions of HTPs with an MRTP claim (n=1190) or no claim (n=1164). HTP use intention and HTP-related harm and use perceptions relative to cigarettes and e-cigarettes were assessed. RESULTS: Overall, participants who viewed versus did not view the claim did not differ in HTP use intention (28.5% vs 28.7%) but were more likely to perceive HTPs as less harmful than cigarettes (11.4% vs 7.0%; p<0.001). The experimental effect on HTP use intention did not differ among past 30-day cigarette smokers versus non-smokers (interaction adjusted OR (AOR)=0.78, 95% CI 0.36 to 1.76) but differed among past 30-day e-cigarette users versus non-users (interaction AOR=1.67, 95% CI 1.02 to 2.68). DISCUSSION: The hypothetical MRTP claim may lower young adults' HTP harm perceptions compared with cigarettes but may not change HTP use intention overall or differentially for cigarette smokers. The larger effect on HTP use intention among e-cigarette users than non-users raises the question of whether MRTP claims may promote HTP use or HTP and e-cigarette dual use among young e-cigarette users.

Association of self-reported use of cannabis for the purpose of improving physical, mental, and sleep health with problematic cannabis use risk.

BACKGROUND: Little is known about health-focused cannabis use purposes and their associations with risk for problematic cannabis use. This cross-sectional study examined three broad cannabis use purposes and association with risk for problematic use among young adult cannabis users who report using for > 1 health reasons. METHODS: Young adults completed an electronic survey as part of an ongoing study on substance use and health. Those who self-reported past 6-month use of ≥ 1 cannabis products-smoking, vaping, dabbing, eating, and blunts-were included in the analysis. Their purposes for use were coded into three categories: sleep, mental, and physical health. Problematic cannabis use (PCU) was measured with the three-level structure Cannabis Abuse Screening Test (CAST-3). Adjusted multivariable regression models were used to estimate use purposes associated with with problematic cannabis use at the p < 0.05 level. RESULTS: Participants (n = 954) were mostly female (63.94%) and Hispanic (54.93%). Mental health was the most endorsed reason (73.38%) for use among study sample. Among participants, 36.3% were classified as being at severe risk (CAST-3 score ≥ 8). There was a significant association between PCU risk and reporting cannabis use for physical health (p < 0.01), mental health, and sleep health (p < 0.01) purposes. Those who used cannabis for physical heath purposes had about four times the risk (adjusted relative risk ratio (aRRR) = 4.38, 95% CI = 3.06-6.69), those who used for mental health had about three times the risk (aRRR = 2.81, 95% CI = 1.86-4.72), and those who used for sleep health had almost two times the risk (aRRR = 1.83, 95% CI = 1.17-2.63) for severe PCU. CONCLUSION: All cannabis use purposes examined increased risk of problematic cannabis use. Physical health use purposes was associated with highest PCU risk. This study demonstrates the risk for cannabis use disorder associated with self-medicating with cannabis.

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.

Secondhand nicotine vaping at home and respiratory symptoms in young adults.

RATIONALE: Despite high prevalence of e-cigarette use (vaping), little is currently known regarding the health effects of secondhand nicotine vape exposure. OBJECTIVE: To investigate whether exposure to secondhand nicotine vape exposure is associated with adverse respiratory health symptoms among young adults. METHOD: We investigated the effect of secondhand nicotine vape exposure on annually reported wheeze, bronchitic symptoms and shortness of breath in the prospective Southern California Children Health Study cohort. Data were collected from study participants (n=2097) with repeated annual surveys from 2014 (average age: 17.3 years) to 2019 (average age: 21.9). We used mixed effect logistic regression to evaluate the association between secondhand nicotine vape and respiratory symptoms after controlling for relevant confounders. RESULTS: Prevalence of secondhand nicotine vape increased from 11.7% to 15.6% during the study period in this population. Prevalence of wheeze, bronchitic symptoms and shortness of breath ranged from 12.3% to 14.9%, 19.4% to 26.0% and 16.5% to 18.1%, respectively, during the study period. Associations of secondhand nicotine vape exposure with bronchitic symptoms (OR 1.40, 95% CI 1.06 to 1.84) and shortness of breath (OR 1.53, 95% CI 1.06 to 2.21) were observed after controlling for vaping, active and passive exposure to tobacco or cannabis, and demographic characteristics (age, gender, race/ethnicity and parental education). Stronger associations were observed when analysis was restricted to participants who were neither smokers nor vapers. There were no associations with wheezing after adjustment for confounders. CONCLUSION: Secondhand nicotine vape exposure was associated with increased risk of bronchitic symptoms and shortness of breath among young adults.

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.

Impact of the e-cigarette era on cigarette smoking among youth in the United States: A population-level study.

To examine and compare trends in past 30-day cigarette smoking among adolescents in the US from 2002 to 2019, before and after the onset of the "e-cigarette era" in 2014. Using National Youth Tobacco Survey (NYTS) data from 2002 to 2019, we modeled the prevalence of past 30-day cigarette smoking over time. A total of n = 274,551 (weighted N = 340,403,754) middle and high school students were included in this study. Interrupted time series analyses were used to examine changes in cigarette smoking over time and compare trends in cigarette smoking pre- and post-2014. Models were applied to the full sample and stratified by middle (6th-8th grade) and high school (9th-12th grade). The observed number of current adolescent cigarette smokers post-2014 was compared to the predicted number, given trends in cigarette smoking prevalence observed pre-2014. Among all students, past 30-day cigarette smoking declined by approximately 0.75% per year from 2002 to 2013 (p < 0.001). Following a significant drop in prevalence from 2013 to 2014 (1.64%; p < 0.001), the decline in past 30-day cigarette smoking slowed significantly to approximately 0.37% per year (p < 0.001), from 2015 to 2019. We estimate that the onset of the "e-cigarette era" in 2014 corresponded to over 1.66 million (95% CI: 1.57 m - 1.75 m) more past 30-day cigarette smokers from 2015 to 2019, cumulatively. The rate of decline in past 30-day cigarette smoking prevalence among adolescents observed since 2002 slowed with the onset of the "e-cigarette era" in 2014, providing evidence at a population-level for the "gateway effect."

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.