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Background: Dual 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 DU can promote smoking cessation. Methods: A systematic search was conducted in accordance with PRISMA guidelines, and all longitudinal studies reporting transitions between DU, exclusive EC use and exclusive CC use were included. Two independent reviewers screened and read all records. Use status transitions among DU were compared to transitions among exclusive e-cigarette users and exclusive CC smokers. Results: 46 records (16 original studies) were identified. Of 16 included studies, eight could be pooled for meta-analysis. The studies showed great heterogeneity, and many presented moderate to high risks of bias. Most DU who changed state transitioned to cigarette smoking. Baseline DU were less likely to report a transition into complete abstinence compared to exclusive CC smokers and exclusive EC users. About one-fifth of DU 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. Conclusion: Current evidence suggests that DU is not a first step towards smoking cessation, with most DU continuing cigarette consumption either through persistent DU or exclusive CC smoking. Relatively fewer DU 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 focused on use status transitions among DU.
Hamoud et al. (Tue,) studied this question.