Inflammatory biomarker changes in healthy adults secondary to electronic cigarette use: A scoping review

Context: There has been a global increase in the use of electronic cigarettes (EC). However, to our knowledge, no review has summarized or categorized changes in inflammatory biomarkers after EC use in the extant literature. Objective: To evaluate changes in general, cardiopulmonary, and oxidative stress-related inflammatory biomarkers in healthy adults who use ECs. Methods: A scoping review was conducted according to the Arksey and O'Malley framework. PubMed and MEDLINE (Ovid) databases were used for our search. After initial pilot searches and discussions, we performed a final search with medical subject headings and plain language terms related to inflammation, biomarkers, ECs, and adult humans. All full-text articles, gray literature, and primary studies dating from the inception of the searched databases to the present were included. Studies of human participants with known confounding medical histories were excluded. Results: Thirty-seven studies met the inclusion criteria. After short-term (<1 month) use, ECs containing nicotine moderately increased cardiovascular (CV) and oxidative stress markers of inflammation. Of all reported results, 50% of CV biomarkers were increased, and 64% of oxidative stress markers were increased. After long-term (>1 month) use, ECs containing nicotine produced mixed results. Two commonly measured biomarkers in this group, matrix metalloproteinase-9 (MMP-9) and interleukin-6 (IL-6), were elevated in 75% and 60% of measured instances, respectively. Conclusion: The results of studies evaluated in our scoping review suggested that short-term use of nicotine-containing ECs may result in increased CV and oxidative stress inflammation, contributing to potential CV or neurologic disease development. The results of studies evaluated in our scoping review also suggested that long-term use of nicotine-containing ECs resulted in no significant changes in general inflammatory biomarker levels. A rigorous systematic review and meta-analysis is necessary to corroborate our findings and to determine the effect of long-term EC use on MMP-9 and IL-6 levels.