Reasons why dual users of e-cigarette and conventional tobacco initiate or maintain dual use. A systematic review.

Some smokers use electronic cigarettes (e-cigs) as an aid to quit smoking or as a harm reduction strategy. However, these smokers may end up using e-cigs and conventional cigarettes, becoming dual users. The main aim of this study was to assess the reasons why dual users use e-cigs. In addition, as a secondary objective, the conflicts of interest and funding of the included studies were analyzed.

Methods: A search was conducted in PubMed, EMBASE, Web of Science and PsychInfo databases until November 2023. Cross-sectional studies were selected that included dual users of conventional tobacco and e-cigs and analyzed the reasons for e-cig use. The Newcastle Ottawa Quality Assessment Scale was applied to assess the quality of the included studies.

Results: Fourteen studies were included. One assessed reasons for initiation, 12 for maintenance of use, and one assessed both separately. Reduction in the number of cigarettes smoked and the perception that e-cigs are less harmful were the main reasons for initiation and maintenance of use. Among the 10 studies that presented a conflict of interest statement, three had conflicts with the pharmaceutical industry. Information on funding was included in 12 studies, of which nine received public funding and one received funding from the pharmaceutical industry.

Conclusions: Identifying the reasons for e-cig use among dual users of e-cigs and conventional tobacco is fundamental for the design of smoking cessation programs and programs aimed at increasing the population's knowledge of new forms of consumption.