Time- and Dose-Dependent Cardiovascular Effects of Nicotine-Containing Electronic Cigarettes in Young Adults: A Systematic Review and Meta-Analysis.

OBJECTIVE

To synthesize the current evidence on the cardiovascular effects of electronic cigarettes (ECs) in young adults (18-30 years), distinguishing between acute and chronic exposure, and comparing their effects to conventional tobacco (CT) use.

METHODS

A systematic review and meta-analysis (PROSPERO: CRD420251072847) was conducted following PRISMA guidelines. A total of 21 studies (12 RCTs, 8 case-control, 1 cohort) involving 17241 participants were included.

RESULTS

Acute EC use, particularly with nicotine, significantly increased systolic blood pressure (SBP: MD = 3.14 mmHg, 95% CI: 0.76 to 5.52), diastolic blood pressure (DBP: MD = 2.05 mmHg, 95% CI: 0.85 to 3.25), and heart rate (HR: MD = 4.23 bpm, 95% CI: 2.10 to 6.37), with effects most pronounced at 0 min post-exposure and dissipating within 1 h. Chronic EC use was associated with reduced endothelium-dependent vasodilation and early atherosclerotic changes. Nicotine-free ECs induced fewer cardiovascular alterations. Comparisons with CT revealed less severe cardiovascular damage with ECs, though still significant when compared to non-smokers.

CONCLUSION

Nicotine-containing EC use in young individuals is associated with modest, predominantly acute and dose-dependent, cardiovascular effects, including transient increases in BP and HR. While initially less harmful than CT, the evidence is largely from cross-sectional studies and acute use, so ECs cannot be considered safe and their use warrants caution in youth.