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. 2025 Mar 20:56:101522.
doi: 10.1016/j.lanwpc.2025.101522. eCollection 2025 Mar.

Trends in smoking prevalence among 14-15-year-old adolescents before and after the emergence of vaping in New Zealand; an interrupted time series analysis of repeated cross-sectional data, 1999-2023

Sam Egger  1 , Michael David  1   2 , Judith McCool  3 , Lucy Hardie  3 , Marianne F Weber  1 , Qingwei Luo  1 , Becky Freeman  4
Affiliations

Trends in smoking prevalence among 14-15-year-old adolescents before and after the emergence of vaping in New Zealand; an interrupted time series analysis of repeated cross-sectional data, 1999-2023

Sam Egger et al. Lancet Reg Health West Pac. .

Abstract

Background: New Zealand experienced a prolonged period of minimal regulation on e-cigarettes until the passing of the 2020 Smokefree Environments and Regulated Products (Vaping) Amendment Act.

Methods: Interrupted time series analyses of the Action for Smokefree 2025 (ASH) Year 10 Snapshot Survey data from 1999 to 2023 to compare changes in smoking trends among 14-15-year-old students (n = 690,470) before and after the advent of vaping in New Zealand (around 2010).

Findings: The prevalence of daily-vaping increased from 1.1% in 2015 (the first year the question was asked) to 1.8% in 2018 before rising to 10.0% in 2023, a nine-fold increase over eight years. From 1999 to 2023, considerable declines in ever-, regular-, and daily-smoking prevalence were observed. However, the rates of decline in ever- and regular-smoking slowed significantly from 2010 onwards (p < 0.001 for both), coinciding with the advent and rapid growth of vaping among New Zealand adolescents. In contrast, the rate of decline in daily-smoking did not significantly change from 2010 onwards (p = 0.066). These findings were robust to sensitivity analyses, including the use of different time series interruption points (change-years) and controlling for inflation-adjusted cigarette prices.

Interpretation: Our findings starkly contrast with those from a previous analysis of ASH data, which suggested that e-cigarettes appear to be displacing smoking among New Zealand youth. Instead, our findings suggest that among 14-15-year-olds, the rapid rise of vaping may have slowed the rates of decline in ever- and regular-smoking, while having little or no impact on the rate of decline in daily smoking. Our findings underscore the importance of effective policy approaches to curb both adolescent vaping and smoking.

Funding: None.

Keywords: Adolescents; Interrupted time series; New Zealand; Segmented logistic regression; Smoking; Tobacco; Vaping; e-cigarettes.

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Conflict of interest statement

MD, MFW, QL, JM and LH declare no conflicts of interest. BF has received payments to her institution from Cancer Council NSW, MRFF/NHMRC, Ian Potter Foundation, and NSW Health. She has also received consulting fees from WHO, NSW Health, Cancer Council Australia, and Sax Institute. Payment for lectures, presentations, and educational events were received from the Department of Health, Government of Hong Kong Special Administrative Region. She has been reimbursed for travel expenses related to her attendance at several conferences including the Oceania Tobacco Control Conference, Australia Public Health Association Conference, Australasian Epidemiology Association, and others. Freeman served as the Director of ASH New Zealand from May 2004 to November 2006, overseeing the delivery of the ASH Year 10 Survey, the data of which is analysed in this manuscript. She has served as an unpaid expert advisor on the Cancer Council–Tobacco Issues Committee, a paid expert member on the NHMRC Electronic Cigarettes Working Committee, an unpaid advisor on the Cancer Institute–Vaping Communications Advisory Panel, and an unpaid expert member on the CHO NSW E-cigarette expert panel. SE is supported by an Australian Government scholarship.

Figures

Fig. 1
Fig. 1
Crude prevalence of ever-vaping, regular-vaping, and daily-vaping among year 10 students aged 14–15 years in New Zealand, 2014–2023. ˆ Question added to the ASH surveys from 2014. ˆˆ Questions added to the ASH surveys from 2015.
Fig. 2
Fig. 2
Observed and background trends estimated from segmented logistic regression models, and crude prevalence for A) Ever-smoking, B) Regular-smoking, C) Daily-smoking.
See this image and copyright information in PMC

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