E-cigarettes and myocardial infarction: A systematic review and meta-analysis

Background: With widespread awareness about the harmful effects of traditional smoking, many people are considering using an e-cigarette. However, many studies have shown that e-cigarettes are not entirely harmless, and their use has been implicated in causing major adverse cardiovascular events. Methods: We adopted the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines to conduct this systematic review. An electronic search was conducted comprehensively through five databases to find the relevant articles. The odds ratio (OR) was used for comparing groups. Meta-analysis was conducted using R statistical software version 3.4.3. A random-effects model was used. Results: A total of 4 studies were included in the analysis incorporating data on 585,306 individuals. Of these, 19,435 were e-cigarettes users, while 1693 used only traditional cigarettes, and 553,095 were non-e-cigarette users. 7.0% of e-cigarettes users suffered an MI (myocardial infarction), while 7.7% and 6.5% of traditional smokers and non-e-cigarettes users suffered an MI. The OR of getting an MI in e-cigarettes (e-cigarettes only or e-cigarettes + traditional smoking) users was 1.33 (95% CI = 1.14-1.56, p-value = 0.01) in comparison to non ecigarette users (traditional smoking or no smoking). While it is 0.61 (95% CI = 0.40-0.93, p-value 0.02) when compared with traditional smoking. Conclusion: Those using e-cigarettes have higher odds of suffering from an MI in comparison to not using e-cigarettes. However, using e-cigarettes is associated with half risk of the risk of MI in comparison to traditional smoking.