The association between e-cigarette use and dyslipidemia: A systematic review and meta-analysis of observational studies

Background: E-cigarette use, also known as vaping, has rapidly increased in recent years, often marketed as a safer alternative to traditional smoking. While the cardiovascular risks of vaping are increasingly being recognized, its relationship with dyslipidemia remains unclear. This systematic review and meta-analysis evaluated the association between e-cigarette use and serum lipid levels, specifically total cholesterol (TC), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and triglycerides (TG). Methods: A search of PubMed, Scopus, EMBASE, CENTRAL, CINAHL, medRxiv, and Google Scholar was conducted up to May 31,2025. Eligible studies included adult populations and assessed the association between exclusive e-cigarette use and lipids. Study quality was assessed using the Methodological Standards for Epidemiological Research (MASTER) scale. Meta-analysis of adjusted odds ratios (aOR) for dyslipidemia and unadjusted weighted mean differences (uWMD) for each lipid was conducted using a bias-adjusted inverse-variance heterogeneity method. Heterogeneity was assessed using the I2 statistic, and publication bias using Doi plots and the LFK index, with the LFK index used as the primary quantitative criterion. Planned subgroup analyses by age group and sex could not be performed due to insufficient stratified reporting in included studies. The overall quality of evidence for each lipid outcome was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework, Results: Of 4,160 identified data sources, seven observational studies from the U.S.A., South Korea, Romania, and Iraq with a total of 25,690 participants met the inclusion criteria. Meta-analysis showed that vaping was associated with higher odds of hypertriglyceridemia (aOR 3.10, 95% CI 1.18 to 8.16, I2 = 80.1%, LFK = 1.34), and higher odds of low HDL (aOR 3.26, 95% CI 2.28 to 4.65, I2 = 3.1%, LFK = 1.41). In studies with unadjusted mean lipid levels, the primary quality-effects model showed no statistically significant difference in TC (unadjusted weighted mean difference (uWMD) +3.66 mg/dL, 95% CI -13.89 to 21.20, I2 = 86.9%, LFK = 9.44) but showed higher LDL (uWMD +12.40 mg/dL, 95% CI 7.91 to 16.88, I2 = 29.1%, LFK = 1.05), and VLDL (uWMD +3.23 mg/dL, 95% CI 1.43 to 5.02, I2 = 0.0%, publication bias not assessed). For all outcomes, the GRADE certainty of evidence was very low. Conclusion: This synthesis suggests that e-cigarette use may be associated with adverse lipid profiles, but the evidence remains observational and of very low certainty, limiting causal inference. Further well-designed longitudinal studies, using validated smoking-status assessment, detailed vaping exposure measures, fasting lipid panels, repeated lipid measurements, and adjustment for key cardiometabolic confounders, are needed to clarify these associations.