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. Author manuscript; available in PMC: 2026 Oct 24.
Published before final editing as: Am J Prev Med. 2026 Sep 14:108576. doi: 10.1016/j.amepre.2026.108576

Patterns of cigarette and electronic nicotine delivery system transitions in U.S. adults, 2021–2024

Andrew F Brouwer 1, Olivia K Roberts 1, Jihyoun Jeon 1, Evelyn Jimenez-Mendoza 1, Stephanie R Land 2, Neal D Freedman 2, Rossana Torres-Alvarez 3,4, Ritesh Mistry 5, David T Levy 6, Rafael Meza 3,4,7
PMCID: PMC13694118  NIHMSID: NIHMS2214287  PMID: 42735867

Abstract

Introduction:

Electronic nicotine delivery systems (ENDS) continue to evolve, and so ongoing analysis of transition rates over time is important for tracking real-world associations between ENDS and cigarette use.

Methods:

A Markov multistate transition model was applied to adults in the Population Assessment of Tobacco and Health Study Waves 6–7 and 7–8 (collected 2021–2024; analyzed 2026), estimating product transition rates and per-year transition probabilities by age group (18–24, 25–34, 35–54, or 55–90 years). These results were compared to estimates from each wave pair in Waves 1–6 (2014–2021).

Results.

ENDS initiation from never use increased from 0.3% (95% confidence intervals [CI]: 0.3, 0.4%) per year in 2019–22 to 0.5% (95%: 0.4, 0.6%) in 2021–22, before returning to 0.3% (95% CI: 0.3, 0.4%) in 2022–24. Similarly, ENDS initiation from cigarette-only to dual use changed from 4.0% (95% CI: 3.6, 4.5%) to 6.8% (95% CI: 6.1, 7.6%) to 5.9% (95% CI: 5.0, 6.7%), respectively. ENDS adoption remained driven by young adults, with respective transition fractions of 1.7% (95% CI: 1.4, 2.0%) and 16.2% (95% CI: 10.6, 21.7%) per year in 2022–24. Persistence of dual use increased, as transitions from dual to cigarette-only and to ENDS-only use each decreased from 26.2% (95% CI: 21.7, 30.7%) and 24.2% (95%CI: 20.5, 27.9%) in 2021–22 to 17.3% (95% CI: 14.3, 20.3%) and 17.9% (95% CI: 15.2, 20.7%), respectively, in 2022–24.

Conclusion.

Public health efforts are needed to reduce persistent dual use and to promote cigarette cessation among older adults.

Keywords: tobacco, cigarette, electronic nicotine delivery system (ENDS), dual use, transition, multistate transition model

Introduction

Among adults, electronic nicotine delivery systems (ENDS) prevalence has continued to increase,1 while smoking has decreased among younger adults, though not older adults.2 The tobacco product marketplace (including synthetic nicotine products) and regulatory environment continues to evolve rapidly in the US. Since October 2021, the US Food and Drug Authority has authorized the marketing of 45 ENDS in the US.3,4 Meanwhile, dominant ENDS brands and their associated characteristics have shifted,5,6 and the sale of oral nicotine pouches rose over the 2019–22 period,7 potentially competing with existing products or initiating new nicotine addiction. These and other changes in the marketplace and regulatory environment may have continued to shift patterns of use and transitions between ENDS and cigarettes. The public health impact of ENDS will likely depend on whether people who would not otherwise quit smoking move from the cigarette to dual to ENDS use (and ideally to non-use) rather than the reverse or persisting in dual use, so ongoing surveillance of these transitions is important for understanding how the public-health impact of ENDS may be changing over time and for projecting future health impacts.

The authors previously used a multistate transition model to analyze how transitions among ENDS and cigarette use changed over Waves 1–6 (2014–21) of the Population Assessment of Tobacco and Health (PATH) Study; this work highlighted substantial differences in product transitions across adult age groups, with lower ENDS adoption among older adults who smoked cigarettes and lower rates of switching from dual to exclusive ENDS use.8–10 Other previous work has noted sustained smoking prevalence among older adults and challenges with helping older adults successfully quit smoking.2,11,12 In the present analysis, these models were extended to examine transitions in Waves 6–8 of PATH (2021–24). The multistage transition model approach estimates the transition rates that underlie observed transitions between products.13–22 Directly estimating these underlying transition rates can help to provide a clearer picture of shifts in use patterns because these rates, unlike empirical transition fractions, are independent of competing transitions (e.g., increasing the fraction transitioning from dual to cigarette-only use reduces the fraction left who can transition to ENDS-only use, even if the underlying smoking cessation rate is unchanged). Although observed changes cannot be tied to any single change in the marketplace or regulatory environment, they help to provide context for how behaviors are changing as result of multiple competing pressures. Additionally, this approach produces parameters that simulation modelers can use to account for current trends in transitions, creating realistic, data-driven status quo and alternative scenarios that can be used to investigate the potential impact of proposed regulations.

Methods

Study Population

The PATH Study is a nationally representative longitudinal cohort study of tobacco and nicotine product use behaviors among the civilian, non-institutionalized US population. This analysis compared 23,803 adults in Waves 6 (March 2021 to November 2021, abbreviated as 2021) and Wave 7 (January 2022 to April 2023, abbreviated as 2022) to 24,756 adults from Wave 7 to Wave 8 (January 2024 to December 2024, abbreviated as 2024). For Waves 6–7 and Waves 7–8, the samples were respectively defined by the “Wave 4 cohort, Wave 6 all-waves weights” and the “Wave 7 cohort, Wave 8 all-waves weights”; the reader is referred to the PATH User Guide for more information on the weights and their associated samples.

The primary aim of this analysis was to estimate overall and age-group-specific transitions for Waves 6–7 and Waves 7–8 and the changes between them, but all previous waves pairs were included for context in longer-term trends.10 Each wave is included two analyses, once as a “to” wave (e.g., Wave 6 to 7) and once as a “from” wave (e.g., from Wave 7 to 8). Follow-up time for participants was approximately one year between Waves 6 and 7 and two years between Waves 7 and 8, and these periods were treated as exactly one and two years in the model. Follow-up between other pairs of Waves were assumed to be either one or two years, as appropriate for the corresponding wave pair. Characteristics of the population for each wave pair are given in Table A.1. This analysis of publicly available data was not regulated as human subjects research (University of Michigan Health Sciences Institutional Review Board HUM00162265).

Measures

Participants were categorized by age group (18–24, 25–34, 35–54, or 55–90 years), sex (male, female), and race and ethnicity (Hispanic, Non-Hispanic Black, Non-Hispanic White). Each participant’s product use was categorized as never established use (of both products), non-current use (of both products), cigarette-only use, ENDS-only use, or dual use of cigarettes and ENDS, as in previous work.8–10 Established cigarette use was defined as having smoked at least 100 cigarettes in one’s lifetime, and established ENDS use was defined as ever having “fairly regularly” used ENDS. Current use of cigarettes and ENDS was defined as ever established and any past 30-day use of that product, and current dual use was defined as established and current use of both cigarettes and ENDS. Non-current use was defined as no past-30-day use of either product by a participant who had previously established use of one or both products; because “former” use is generally understood to refer to longer-term cessation, “non-current” is used to describe no past-30-day use. Daily use of either product was defined as use on 30 of the past 30 days. Participants were excluded from the analysis if they were missing any covariate or product use state; e.g., 17% of the Wave 6 to 7 sample was excluded.

Statistical Analysis

The authors applied a multistate transition model to analyze the underlying transition hazard rates between the product use categories for adults overall and in each of the age categories. Multistate transition models assume that transitions arise from a finite-state, Markov stochastic process where transition hazard rates depend only on the current state and not on past states or transition history. Technical details of the multistate transition model are provided in the Appendix. Using discrete-time observations, the model estimated the instantaneous risk of transition from one state to another, i.e., transition hazard rates, which collectively define the probability of transitioning from one state to any other at a future time.

PATH replicate weights associated with the sample weights described above were used to calculate variance and confidence intervals, as described in the PATH user guide. In preliminary model analysis using the PATH weights as-is, the estimated transition probabilities transitions between dual and ENDS use for Waves 6 to 7 were more than 5 percentage points different than the empirical fraction (Figure A.1). This result meant that the model was sacrificing fit for product use categories with fewer participants to make small improvements in the fit for categories with greater numbers of participants. Because the authors wanted to estimate transition rates that best reproduce transitions within each product use category, a modeling decision was made to give equal weight to each product use state by renormalizing the weights across product use categories. This reweighting approach resulted in probabilities that better reflected the observed empirical transition fractions, as discussed in the Appendix. For consistency across the analyses, transitions were re-estimated for all previous waves with the renormalized weights, although re-normalization had little effect on most transitions in previous waves (Figure A.2).

Using the estimated transition rates, 1-year transition probabilities were calculated overall and for each age group for each wave pair separately. Transition probabilities account for the possibility of multiple transitions between product use states over the period. For Waves with a two-year gap, the one-year transition probabilities reflect estimated transition fractions per year over the two-year period. Additional details on point estimate and variance calculation are given in the Appendix.

Additionally, associations between transition rates and non-daily vs daily use of each product were estimated for relevant transitions, e.g., daily vs non-daily cigarette use was a predictor of the transitions from cigarette and from dual use, but not from never, non-current, or ENDS use. These associations were estimated in multivariable models adjusting for sex, age group, race and ethnicity for each wave pair using the renormalized weights. All multistate transition models were estimated using the wmsm function8 in R (v1.4.1, publicly available at https://tcors.umich.edu/Resources_Research.php), which is an extension of the msm function23 modified to incorporate survey weights.

Results

In Waves 6 (2021) and 7 (2022), the average weighted prevalences of never established use were 57.3% and 58.6%, the prevalences of non-current use were 25.3% and 24.5%, the prevalences of current cigarette-only use were 12.7% and 11.2%, the prevalences of current ENDS-only use were 3.2% and 4.1%, and the prevalences of current dual cigarette and ENDS use were 1.5% and 1.7% (Table A.1). Between 2021–22 and 2022–24, all transition rates statistically significantly decreased, except for cigarette initiation, which for the decrease was not statistically significant (Figure 1A; a comparison to all previous rates is given in Figure A.3). One-year transition heatmaps for 2021–22 and 2022–24 are given in Figure 1B and C, and longer-term trends are visualized in transition probabilities overall in Figure 2 and by age group in Figure 3. Values of the transitions and their confidence intervals are given in Table A.2.

Figure 1:

Figure 1:

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A) Transition hazard rates among adults in 2021–22 (Waves 6–7) and 2022–24 (Waves 7–8). A version of this figure including previous results from 2014–21 (Waves 1–6) is given in Figure A.3. B) Estimated one-year transition probabilities for adults in 2021–22 (Waves 6–7), and C) 2022–24 (Waves 7–8). Confidence intervals for B and C are provided in Table A.2.

Figure 2:

Figure 2:

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Estimated one-year transition probabilities and 95% confidence intervals for adults, PATH Waves 1-8 (2014–24), by product use state. The x-axis is spaced by the year of the “from” Wave, and the y-axis is the modeled transition percentage per year between the pair of Waves. Please note the y-axis range is different across product use categories. Point estimates and confidence intervals are provided in Table A.2.

Figure 3:

Figure 3:

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One-year transition probabilities and 95% confidence intervals for adults, PATH Waves 1-8 (2014–24), by transition and age group (years). The x-axis is spaced by the year of the “from” Wave, and the y-axis is the modeled transition percentage per year between the pair of Waves. Please note the y-axis range is different across product use categories. Point estimates and confidence intervals are provided in Table A.2.

Cigarette initiation from never established use continued to decline to 0.1% and <0.1% 2021–22 and 2022–24 (Figure 1C; Figure 2A). ENDS initiation transiently increased from 0.3% (95% CI: 0.3, 0.4%) in 2019–22 to 0.5% (95% confidence intervals [CI]: 0.4, 0.6%) in 2021–22, before returning to 0.3% (95% CI: 0.3, 0.4%) in 2022–24. ENDS initiation was driven by young adults, 2.7% (95% CI: 2.2, 3.2%) of whom initiated ENDS-only use in 2021–22 and 1.7% (95% CI: 1.4, 2.0%) in 2022–24 (Figure 3B). Other transitions representing adoption of ENDS use also experienced a large jump in 2021–22 follow by a decrease to an intermediate value in 2022–24: from non-current to ENDS-only use (from 1.0% [95% CI: 0.8, 1.2%] in 2019–21 to 2.7% [95% CI: 2.3, 3.2%] in 2021–22 to 1.9% [95%CI: 1.6, 2.2%] in 2022–24; Figure 2B) and from cigarette-only to dual use (from 4.0% [95% CI: 3.6, 4.5%] to 6.8% [95% CI: 6.1, 7.6%] to 5.9% [95% CI: 5.0, 6.7%]; Figure 2C). These patterns were also largely driven by young adults (Figure 3D and F). Among young adults, 23.6% (95% CI: 20.2, 27.0%) and 13.7% (95% CI: 11.3, 16.2%) of those in the non-current use state transitioned to ENDS-only use in 2021–22 and 2022–24, respectively (Figure 3D), up from 9.2% (95% CI: 6.8, 11.7%) in 2019–21. Similarly, 19.2% (95% CI: 14.0, 24.5%) and 16.2% (95% CI: 10.6, 21.7%) of those using cigarettes only transitioned to dual use (Figure 3F), compared to 14.2% (95% CI: 11.5, 16.9%) in 2019–21.

Transitions from ENDS-only to dual use remained relatively low in 2021–22 (6.0%, 95% CI: 4.6, 7.3%) and 2022–24 (4.5%, 95% CI: 3.5, 5.5%; Figure 2D), with little difference by age group (Figure 3H). Transitions from ENDS-only to non-current transiently increased from 18.3% (95% CI: 16.4, 20.2%) in 2019–21 to 23.3% (95%CI: 20.5, 26.2%) in 2021–22 before dropping to 15.4% (95% CI: 13.5, 17.3%) in 2022–24 (Figure 2D). Interestingly, the previous age gradient in this transition collapsed in 2022–24 (Figure 3G).

Transitions from dual use to cigarette-only use initially remained approximately one quarter (26.2% [95% CI: 21.7, 30.7%] in 2021–22; Figure 2E) before declining to 17.3% (95% CI: 14.3, 20.3%) in 2022–24. This transition remained least common for young adults at 14.2% (95% CI: 7.9, 20.4%) in 2012–22 and 9.6% (95% CI: 4.6, 14.7%) in 2022–24 and more common for older adults (Figure 3I). The increase in transitions from dual to ENDS-only use (from 17.0% [95% CI: 14.2, 19.9%] in 2019–21 to 24.2% [95% CI: 20.5, 27.9%] in 2021–22), was initially driven by young adults (34.4% [95% CI: 26.2, 42.6%]; Figure 3J) and adults ages 25–34 years (29.4% [95% CI: 23.1, 35.7%]). The age gradient appeared to diminish in 2022–24, although the apparent jump for ages 55–90 years in the dual to ENDS-only transition was not statistically significant.

Full results of the multivariable transitions models with transitions hazard ratios for product use frequency and the other covariates are given in Table A.3. For brevity, here only select results for product use frequency in 2021–22 and 2022–24 are highlighted. Among adults who smoked cigarettes only, participants who smoked cigarettes non-daily had a higher rate of transitioning to non-current use (hazard ratio [HR] 6.54 [95% CI: 4.70, 9.09] and 4.13 [95% CI: 3.02, 5.63] in 2021–22 and 2022–24) than those who smoked daily. Similarly, among those who used both ENDS and cigarettes, those who smoked cigarettes non-daily had a higher rate of transitioning to ENDS-only use (HR 3.07 [95% CI: 2.06, 4.57] and 2.52 [95% CI: 1.63, 3.91]) than those who smoked daily. The HRs by cigarette use frequency for the cigarette-only to dual use and from dual to cigarette-only use transitions were not statistically significant in 2021–22, but the dual to cigarette-only use transitions was statistically significantly lower for those who smoked non-daily in 2022–24 (HR 0.58 [95% CI: 0.36, 0.94]). Among adults who only vaped ENDS, those who vaped ENDS non-daily transitioned to non-current use at a higher rate (HR 2.62 [95% CI: 1.99, 3.45] and 2.82 [95% CI: 2.13, 3.74]) than who vaped daily, and, similarly, among those who used both products, those who vaped non-daily transitioned to ENDS-only use at a lower rate (HR: 0.59 [95% CI: 0.35, 0.98]) than those who vaped daily in 2021–22 (the HR was not statistically significant in 2022–24). Vaping frequency was not statistically significant associated with the ENDS-only to dual use or the dual to cigarette-only use transition rate in either period.

Discussion

In this analysis, the authors continued to track changes in transition rates between never, non-current, cigarette-only, ENDS-only, and dual use of both products among adults in the PATH Study, here adding transitions from Waves 6–8. In this period (2021–24), a large jump and subsequent small decline was observed in transitions representing the adoption of ENDS—from never established use, from non-current use, and from cigarette-only use to dual use. Transitions from dual use declined in between 2021–21 and 2022–24, resulting in the persistence of dual use increasing from about 40% to about 60% per year. Marked differences by age group were seen, with most ENDS adoption driven by young adults (ages 18–24 years) and, to a lesser extent, adults ages 25–34 years. Similarly, the increase in transitions from dual to ENDS-only use in 2021–22 (24.2%, catching up with transitions from dual to cigarette-only use, 26.2%), was again driven by the two younger age groups. Overall, there was comparatively little significant change for adults ages 35–54 and 55–90 years, where ENDS use and transitions to ENDS use remain low, and cigarette smoking cessation rates remained largely stagnant. It is difficult to interpret the recent and longer-term changes as a result of any specific regulatory or marketplace changes; as highlighted earlier, FDA has authorized marketing of some ENDS, the dominant brands in the ENDS marketplace have changed, and sales of oral nicotine pouches have been increasing.3–7,24 Ultimately, this work is descriptive, tracking how, if not why, product transitions have shifted.

While ENDS are not harmless,25–27 they are likely less harmful than combustible cigarettes.28–30 They have been promoted as cigarette cessation aids, but they are not FDA-approved for smoking cessation. The authors found a greater propensity for younger adults to transition from cigarette-only to dual to ENDS-only use, with both transitions along this pathway comparatively rarer for older adults. For example, in 2021–22, transitions from cigarette-only to dual use for older adults ages 55–90 were only 2.4% compared to 19.2% for younger adults (1.8% and 16.1%, respectively in 2022–24), and transitions from dual use to ENDS-only for older adults were 12.0% compared to 34.4% among younger adults (although the gap may have decreased in 2022–24). These results are consistent with prior work that has highlighted sustained smoking prevalence among older adults and challenges with helping older adults successfully quit smoking.2,11,12 Because ENDS do not seem to be contributing to smoking cessation among older adults in a substantial way in the current marketplace, public health efforts are needed to promote cigarette cessation in older adults. Many studies have emphasized the need for health communication targeted to older adults, specifically,31–33 as health communication strategies that work for young adults may not be successful for older adults. Targeting to older adults may include the development of messaging focusing on common health beliefs, motivations, and risk misperceptions held by older adults, as well as addressing age-relevant health outcomes such as the impacts of smoking on cognition, heart disease, and cancer survival.31

Previous iterations of this transition surveillance have highlighted hazard ratios by sociodemographic factors8 and continuous age9 and how transition probabilities translate into numbers of people at the population level.10 In this analysis, the authors highlighted associations between non-daily vs daily use of cigarettes and ENDS. Unsurprisingly, participants who used a product non-daily were found to transition to non-current use at a greater rate than those who reported using that product daily, for both cigarettes and ENDS. Among those who used both products and smoked cigarettes non-daily, transitions to ENDS-only use occurred at a greater rate compared to those who smoked daily. Conversely, participants who vaped non-daily and smoked cigarettes transitioned to ENDS-only use at a lower rate than those who vaped daily. Prior work has also found associations between daily vaping and smoking cessation,34–36 although other studies have not found an association.37 The results highlight an important challenge for those promoting transitions along the longer-term trajectory of cigarette-only to dual use to ENDS-only use to non-current use for people who smoke cigarettes and would not otherwise quit: successful transitions from dual to ENDS-only use are more likely among those frequently using ENDS, but frequent ENDS use is associated with reduced ENDS cessation. Moreover, there would be no public health benefit if adults who smoke adopted ENDS and remained in dual use without reducing their smoking frequency, or if vaping promotes smoking relapse, as has been found in some studies.35,38,39 Additional work is needed to better understand who might benefit from ENDS-mediated smoking cessation, especially if cessation through FDA-approved medication and counseling is not successful, and how to reduce the likelihood of long-term ENDS-only use after smoking cessation. Additionally, it will be helpful for tobacco use surveillance to distinguish behaviors by frequency of use and for studies to more explicitly consider associations between product characteristics and transitions in frequency of use, not just any use of the products.

Limitations

The strengths of this analysis include the use of the large, nationally representative longitudinal PATH Study data. Additionally, the use of multistate transition models allowed for the disentanglement of the underlying competing transition rates from the observed transition fractions and explicitly account for non-uniform time between PATH Waves. However, this work did not account for participants’ use of other tobacco and nicotine products. Future work will likely need to directly consider how current oral nicotine pouch use is associated with transitions among cigarette and ENDS use. Additionally, the states in the main analysis combined individuals regardless of frequency of use, not distinguishing between those who used a product, e.g., 5 vs 30 days in the past 30; although previous work considered how different thresholds of use affected transition estimates,19 the authors did not reproduce that analysis with the most recent data because of the added complexity.

Conclusions

In this analysis, the authors found that transitions involving cigarettes and ENDS have continued to change over time for adults in the US. Many of the changes involving the adoption of ENDS or transitions from dual use of both products to ENDS-only use were driven by young adults, with little-to-no change among older adults. Public health efforts targeting older adults who smoke are needed to help this population to quit cigarettes, either by switching to ENDS-only or, ideally, completely quitting all nicotine products.

Supplementary Material

Appendix A

Acknowledgments

Declaration of interest: The authors have no competing interests to declare. Funding: This project was funded through National Cancer Institute (NCI) and Food and Drug Administration (FDA) grant U54CA229974. The opinions expressed in this article are the authors’ own and do not reflect the views of the National Institutes of Health, the Department of Health and Human Services, or the United States government.

Data availability statement

Public Use Files from the Population Assessment of Tobacco and Health Study are available for download from an open access repository (https://doi.org/10.3886/ICPSR36498.v25). PATH Restricted-use files (https://doi.org/10.3886/ICPSR36231.v47) require a restricted data use agreement. Conditions of use are available on the aforementioned websites.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Appendix A
NIHMS2214287-supplement-Appendix_A.pdf (1.9MB, pdf)

Data Availability Statement

Public Use Files from the Population Assessment of Tobacco and Health Study are available for download from an open access repository (https://doi.org/10.3886/ICPSR36498.v25). PATH Restricted-use files (https://doi.org/10.3886/ICPSR36231.v47) require a restricted data use agreement. Conditions of use are available on the aforementioned websites.

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