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

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.