Objective: Increasing e-cigarette use combined with emerging evidence of their respiratory effects raises concerns about their potential impact on asthma prevalence. This review evaluates the most recent available evidence on the association of e-cigarette use and asthma world-wide.
Methods: A literature search was performed in PubMed, Scopus, CINAHL, Cochrane Library, Web of Science and ProQuest in March 2021. This study was conducted in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) registered with PROSPERO (registration number: CRD42020211812).
Study selections: Cross-sectional and cohort studies assessing the association between e-cigarette use and asthma were eligible for inclusion. Studies examining exacerbations in asthma symptoms and severity were excluded. The quality of the included studies was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS).
Results: Thirteen cross-sectional studies with the sample size of 1,039,203 met the eligibility criteria. Odds ratios were pooled using a random effects model. Pooled analysis found a significant association between current e-cigarette use and asthma (pOR = 1.36, 95% CI 1.21-1.52) and ever e-cigarette use and asthma (pOR = 1.24 95% CI 1.13-1.36).
Conclusion: Our review found that e-cigarette use and ever e-cigarette use are correlated with asthma. However, heterogeneity and inconsistencies between covariates limited the interpretation of the results. This warrants further studies to investigate any potential causal association between e-cigarette use and asthma. No funding was received for this systematic review.