What Are the Effects of Electronic Cigarettes on Lung Function Compared to Non-Electronic Cigarettes? A Systematic Analysis

Objective: The effects of e-cigarettes on lung function were compared between the e-cigarette and the non-e-cigarette group, as well as self-changes after inhaling e-cigarettes. Method: From March 1st, 2022, relevant literature was selected from four databases through a predefined retrieval strategy. Strict literature screening and quality evaluation were conducted. The study followed PRISMA guidelines. Results: Our results showed that CO (SMD: −1.48, 95%: −2.82–0.15) and FeNO (SMD: −0.66, 95%: −1.32, −0.01) were significantly decreased after e-cigarette usage. Only asthmatic smokers showed a statistically significant increase in flow resistance after inhaling e-cigarettes. Conversely, the decrease of FEV1/FVC% in the non-e-cigarette groups exceeded that in the e-cigarette group (SMD:1.18, 95%: 0.11–2.26). The degree of O(2) saturation decrease was also less than that for the cigarette groups (SMD:0.32, 95%: 0.04–0.59), especially when compared to the conventional cigarette group (SMD:0.56, 95%: 0.04–1.08). Conclusion: The current findings indicate that short-term e-cigarette inhalation has a similar (but not significant) effect on lung function, as compared with non-e-cigarettes. More clinical studies are needed to explore the safety of inhaling e-cigarettes, especially in vulnerable populations.