Background: Electronic cigarette (e-cigarette) use is gaining popularity among adults. Monitoring e-cigarettes-induced respiratory symptoms is crucial for both clinical and regulatory purposes. We systematically reviewed the current literature to understand the prevalence of respiratory symptoms among exclusive e-cigarette users, dual users, and former smokers. Methods: Databases included PubMed, CINAHL, Cochrane Library, Embase, and Scopus. We included all English-language, empirical quantitative papers that explored the prevalence of e-cigarettes-related respiratory symptoms. Random-effects models were utilized in conducting the meta-analyses. The quality of identified studies was evaluated using the NIH Study Quality Assessment Tools. This study is registered with PROSPERO(#CRD42020165973). Results: The literature search identified 1,240 references. After removing duplicates and screening for eligibility, 168 studies were included in the final review. The majority of included studies reported a wide range of adverse respiratory symptoms. The respiratory symptoms were prevalent among the exclusive e-cigarette users, dual users, and those who switched from combustible cigarettes to an e-cigarette. Further, out of the randomized controlled trials, 5 were rated as good quality, while 3 were rated as fair. Among the observational studies, 24 were rated as good quality, and 9 were rated as fair. The two experimental studies were both rated as fair quality. Conclusions: In this systematic review, our meta-analyses of exclusive e-cigarette users, dual e-cigarette users, and transitioning e-cigarette users demonstrated significant incidences of various respiratory symptoms, emphasizing the impact of e-cigarette usage on respiratory health and the need for further research in this area. Effective e-cigarette cessation interventions are needed to prevent respiratory symptoms and respiratory disease and subsequently improve health outcomes. The results from this study will inform clinical recommendations/guidelines for e-cigarette users and dual users of e-cigarettes and traditional cigarettes.
Alqahtani et al. (Sun,) studied this question.