Abstract
Background Use of electronic cigarettes (e-cigarettes) is prevalent among adolescents and young adults but there has been limited knowledge about health consequences in human populations. We conduct a systematic review and meta-analysis of results on respiratory disorder from studies of general-population samples and consider the mapping of these results to findings about biological processes linked to e-cigarettes in controlled laboratory studies.
Method We conduct a literature search and meta-analysis of epidemiological studies on the association of e-cigarette use with asthma and with chronic obstructive pulmonary disease (COPD). We then discuss findings from laboratory studies about effects of e-cigarettes on four biological processes: cytotoxicity, oxidative stress/inflammation, susceptibility to infection, and genetic expression.
Results Epidemiological studies, both cross-sectional and longitudinal, show a significant association of e-cigarette use with asthma and COPD, controlling for cigarette smoking and other covariates. For asthma (n=15 studies), the pooled adjusted odds ratio (AOR) was 1.39 (CI 1.28–1.51); for COPD (n=9 studies) the AOR was 1.49 (CI 1.36–1.65). Laboratory studies consistently show an effect of e-cigarettes on biological processes related to respiratory harm and susceptibility to illness, with e-cigarette conditions differing significantly from clean-air controls though sometimes less than for cigarettes.
Conclusions The evidence from epidemiological studies meets established criteria for consistency, strength of effect, temporality, and in some cases a dose-response gradient. Biological plausibility is indicated by evidence from multiple laboratory studies. We conclude that e-cigarette use has consequences for asthma and COPD, which is of significant concern for respirology and public health.
Footnotes
This manuscript has recently been accepted for publication in the European Respiratory Journal. It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article.
Conflict of interest: Dr. Yan reports grants from National Institutes of Health, during the conduct of the study;.
Conflict of interest: Dr. Wills reports grants from National Cancer Institute , during the conduct of the study;.
Conflict of interest: Dr. Soneji has nothing to disclose.
Conflict of interest: Dr. Choi has nothing to disclose.
Conflict of interest: Dr. Jaspers has nothing to disclose.
Conflict of interest: Dr. Tam has nothing to disclose.
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- Received September 23, 2019.
- Accepted October 10, 2020.
- Copyright ©ERS 2020