CARDIOVASCULAR EFFECTS OF ELECTRONIC CIGARETTE USE : A SYSTEMATIC REVIEW OF PRIMARY HUMAN STUDIE
Abstract
Background Electronic cigarettes (ECUs), also known as electronic nicotine delivery systems (ENDS) or vaping devices, have experienced unprecedented global adoption since the early 2000s. Despite marketing as reduced-harm alternatives to combustible cigarettes (CCs), accumulating evidence implicates ECU aerosol constituents—including nicotine, ultrafine particles, heavy metals, and volatile aldehydes—in multiple cardiovascular pathological mechanisms. This systematic review aimed to comprehensively characterize the association between ECU use and cardiovascular disease (CVD) risk across 15 distinct cardiovascular outcome domains, address the existing research gap of sparse longitudinal primary evidence, and evaluate the differential CVD risk profile according to tobacco use pattern. Methods The study strictly adhered to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines. Included study designs were restricted to primary studies: randomized controlled trials (RCTs), cohort studies, case-control studies, cross-sectional studies, and other primary observational or experimental designs. Systematic reviews and meta-analyses were explicitly excluded from the characteristics table and primary analysis. Risk of bias was assessed using the Newcastle-Ottawa Scale (NOS) for observational studies and the Cochrane RoB 2.0 tool for RCTs. Results Twenty primary studies were included (8 RCTs, 9 cross-sectional studies, 3 retrospective cohorts, 1 prospective cohort, 1 case-control; total n >1.1 million participants, 6 countries). Risk of bias was predominantly low to moderate. Key findings across 15 outcomes: (1) daily ECU use was independently associated with 79% higher odds of MI (OR 1.79, 95%CI 1.20–2.66, p=0.004); (2) dual ECU + CC use was associated with 27–144% higher odds of composite CVD; (3) ECU use acutely elevated systolic BP by 9.6 mmHg and significantly impaired endothelial function; (4) chronic ECU use produced progressive arterial stiffness, coronary microvascular dysfunction, and elevated oxidative stress; (5) complete switching from CC to ECU post-PCI was associated with significantly lower MACE risk (HR 0.82, 95%CI 0.69–0.98); (6) exclusive ECU use was not independently associated with incident hypertension (aHR 1.00) in prospective longitudinal data. Conclusion Current evidence suggests that electronic cigarette use, particularly dual use with combustible cigarettes, is associated with increased cardiovascular risk across multiple biological and clinical outcomes. Although complete switching from combustible cigarettes may provide relative cardiovascular benefit among established smokers, electronic cigarettes should not be regarded as harmless, especially among never-smokers. Further high-quality prospective studies are needed to clarify long-term cardiovascular safety.Keywords
electronic cigarette, e-cigarette, vaping, ENDS, cardiovascular disease, myocardial infarction, arterial stiffness, endothelial dysfunction, oxidative stress