Trends in adolescent smoking prevalence before and after the emergence of vaping in Australia: an interrupted time series analysis, 1999-2023.

Objective: To compare adolescent smoking trends in Australia before and after the emergence of e-cigarettes in about 2010, to evaluate the potential impacts of adolescent vaping on smoking prevalence.

Design: Repeated cross-sectional study.

Setting: Australian secondary schools.

Participants: 172 406 students aged 12-17 years who took part in the Australian Secondary Students' Alcohol and Drug Survey between 1999 and 2023.

Main outcome measures: Prevalence of ever, past year, past month and past week smoking for 12-17-year-olds, and daily smoking for 14-15-year-olds.

Results: From 2014 to 2022-2023, the prevalence of ever vaping among students increased 2.3-fold (from 13.2% to 29.9%), while past month vaping increased 4.8-fold (from 3.3% to 15.7%). From 1999 to 2022-2023, there were substantial declines in the prevalence of ever, past year, past month, past week and daily smoking among students, with reductions ranging between 74% and 89%. However, the rates of decline for these five measures of smoking slowed significantly from 2010 onwards, coinciding with the emergence of vaping. By 2022-2023, there were, respectively, 74 (95% confidence interval [CI], 67-80), 54 (95% CI, 48-60), 25 (95% CI, 21-29) and 16 (95% CI, 12-19) more 12-17-year-olds per 1000, and 7 (95% CI, 4-9) more 14-15-year-olds per 1000 who had engaged in ever, past year, past month, past week and daily smoking than projected by smoking trajectories from the pre-vaping era. These findings were robust to sensitivity analyses, including the use of different time series interruption points (change-years) and controlling for the affordability of cigarettes.

Conclusion: Australia's remarkable progress in reducing adolescent smoking has slowed since the emergence of vaping, underscoring the need for integrated tobacco and vaping control strategies.