A Systematic Review Investigating the Impact of Dual Use of E-Cigarettes and Conventional Cigarettes on Smoking Cessation

Abstract

BackgroundDual use (DU) of conventional cigarettes (CC) and e-cigarettes (EC) has emerged as a common pattern among youth and adult populations. This review aims to investigate whether dual use can promote smoking cessation.MethodsA systematic search was conducted in accordance with PRISMA guidelines, and all longitudinal studies reporting transitions between DU, exclusive e-cigarette use and exclusive conventional cigarette use were included. Two independent reviewers screened and read all records. Use status transitions among dual users were compared to transitions among exclusive e-cigarette users and exclusive CC smokers.ResultsForty-six records (sixteen original studies) were identified. Of sixteen included studies, eight could be pooled for meta-analysis. The studies showed great heterogeneity, and many presented moderate to high risks of bias. Most dual users who changed state transitioned to cigarette smoking. Baseline dual users were less likely to report a transition into complete abstinence compared to exclusive CC smokers and exclusive EC users. About one-fifth of dual users remained in the same use status after >16–24 months, exposing them to DU for a prolonged time. After >24–48 months, 8% of DU maintained DU.ConclusionCurrent evidence suggests that DU is not a first step toward smoking cessation, with most DUs continuing cigarette consumption either through persistent DU or exclusive CC smoking. Relatively fewer dual users transitioned into complete nicotine abstinence compared to exclusive CC and exclusive EC users. The concerns raised about limitations of current evidence highlight the need for more research focussed on use status transitions among dual users.