E-cigarette and cigarette use trajectories among young people in England: a cross-sectional, retro- and prospective analysis of the Smoking Toolkit Study

Background: E-cigarettes are an effective harm reduction and cessation aid.

However, there are concerns regarding their impact on youth, particularly gateway effects leading to the uptake of conventional cigarettes.

While use of e-cigarettes among youth in England remains low, this is a fast-changing environment, and limited data exist to assess the interconnected trajectories of e-cigarette and cigarette use.

This proposal aims to evaluate whether or not e-cigarettes can contribute towards a tobacco-free UK and thus reduce the associated cancer burden.

Aims: This study will investigate cross-sectional associations, retro-and prospective trajectories of e-cigarette and cigarette use among youth in England to determine a) reciprocal associations of e-cigarette and cigarette use; b) the impact of initiation with e-cigarettes on current cigarette use and vice versa, and c) the impact of dual use of cigarette with e-cigarettes on subsequent quitting activity.

Methods: This proposal involves the CRUK-funded Smoking Toolkit Study (STS), a national household survey representative of the English population with one-year follow-up that assesses key indicators of tobacco and e-cigarette use.

Three additional questions will be added to the STS for respondents aged 16-25 for two years to determine ever and past regular use of e-cigarettes and product initiation.

Cross-sectional analysis (N=~6,600) will explore patterns of associations between ever, past regular and current cigarette and e-cigarette use in cross-lagged panel analysis, describe use characteristics and socio-demographic correlates.

Retrospective analysis (N=~660-1980) will compare ever, past regular and current cigarette use in youth who first used an e-cigarette (exposure group) and propensity score matched adolescents without initial e-cigarette use (control group). The inverse association with e-cigarette use as the outcome will also be assessed.

Prospective analysis (N=~400) will evaluate the impact of baseline dual use of cigarettes and e-cigarettes on use of cigarette or e-cigarettes at 12 months follow-up compared with baseline use of cigarettes alone, controlling for known confounders, using logistic regression. Qualitative thematic analysis of focus groups will supplement quantitative findings.

How results will be used: The cross-sectional analysis will provide up-to-date insights into trajectories of product use and describe use characteristics, including source of purchase.

The retrospective analysis will determine whether initiation with e-cigarettes acts as a gateway to subsequent cigarette smoking and determine the strength of the inverse pathway. The prospective analysis will evaluate whether dual use negatively affects later quitting activity. We plan to publish these analyses and share them with relevant stakeholders to inform policy decisions on e-cigarettes.