Objectives Given that many adolescent e-cigarette users are never-smokers, the possibility that e-cigarettes may act as a gateway to future cigarette smoking has been discussed in various studies. Longitudinal data are needed to explore the pathway between e-cigarette and cigarette use, particularly among different risk groups including susceptible and non-susceptible never-smokers. The objective of this study was to examine whether baseline use of e-cigarettes among a sample of never-smoking youth predicted cigarette smoking initiation over a 2-year period.
Design Longitudinal cohort study.
Setting 89 high schools across Ontario and Alberta, Canada.
Participants A sample of grade 9–11 never-smoking students at baseline (n=9501) who participated in the COMPASS study over 2 years.
Primary and secondary outcome measures Participants completed in-class questionnaires that assessed smoking susceptibility and smoking initiation.
Results Among the baseline sample of non-susceptible never-smokers, 45.2% of current e-cigarette users reported trying a cigarette after 2 years compared with 13.5% of non-current e-cigarette users. Among the baseline sample of susceptible never-smokers, 62.4% of current e-cigarette users reported trying a cigarette after 2 years compared with 36.1% of non-current e-cigarette users. Overall, current e-cigarette users were more likely to try a cigarette 2 years later. This association was stronger among the sample of non-susceptible never-smokers (AOR=5.28, 95% CI 2.81 to 9.94; p<0.0001) compared with susceptible never-smokers (AOR=2.78, 95% CI 1.84 to 4.20; p<0.0001).
Conclusions Findings from this large, longitudinal study support public health concerns that e-cigarette use may contribute to the development of a new population of cigarette smokers. They also support the notion that e-cigarettes are expanding the tobacco market by attracting low-risk youth who would otherwise be unlikely to initiate using cigarettes. Careful consideration will be needed in developing an appropriate regulatory framework that prevents e-cigarette use among youth.
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Contributors STL designed the study. SA and AC formulated the research objectives and plan. Analysis of data was performed by WQ. SA and AC prepared the manuscript. All authors made revisions to the original draft and approved the final submitted version.
Funding The COMPASS study was supported by a bridge grant from the Canadian Institutes of Health Research (CIHR) Institute of Nutrition, Metabolism and Diabetes through the ‘Obesity—Interventions to Prevent or Treat’ priority funding awards (OOP-110788; grant awarded to STL) and an operating grant from the CIHR Institute of Population and Public Health (IPPH) (MOP-114875; grant awarded to STL). STL is a Chair in Applied Public Health funded by the Public Health Agency of Canada in partnership with CIHR. AC is funded by CIHR.
Competing interests None declared.
Patient consent Not required.
Ethics approval Ethics approval was received by the University of Waterloo’s Office of Research Ethics and all participating school boards’ research ethics bodies.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement COMPASS data is stored at the University of Waterloo on a secure server. The principal investigator of COMPASS, STL, maintains ownership of all COMPASS data and will grant access to COMPASS research collaborators, external research groups and students. For researchers looking to gain access to COMPASS data, individuals must successfully complete the COMPASS data usage application form, that is available online (https://uwaterloo.ca/compass-system/information-researchers), which is then reviewed and approved/declined by STL.
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