Associations of exclusive e-cigarette use and dual use of e-cigarettes and combustible cigarettes with prevalent and incident hypertension: A systematic review and meta-analysis.

Introduction: The relationship between electronic cigarette (e-cigarette) use and hypertension remains uncertain. Existing evidence is difficult to interpret because of differences in exposure classification, smoking history, dual use, study design, and hypertension ascertainment. We systematically reviewed and meta-analysed population-based observational studies examining associations between exclusive e-cigarette use, dual use of e-cigarettes and combustible cigarettes, and prevalent and incident hypertension. Methods: Following PRISMA, we searched PubMed/MEDLINE, Embase, Scopus, and Web of Science from inception to 31 May 2026. Eligible cross-sectional or longitudinal observational studies reported exposure-specific associations with prevalent or incident hypertension. Exclusive e-cigarette use was defined as current or recent e-cigarette use without concurrent combustible-cigarette use, and dual use as concurrent use of both products. Hypertension was ascertained through self-reported or clinician diagnosis, electronic health records, antihypertensive medication use, or a study-defined measured blood-pressure threshold. Acute experiments, studies reporting only continuous blood-pressure outcomes, interventional switching studies, and reports without extractable estimates were excluded. Adjusted estimates were pooled using random-effects restricted maximum likelihood models. Risk of bias was assessed using ROBINS-E, and certainty of evidence was evaluated using GRADE. Results: Of 3988 records identified, 10 studies were included: six cross-sectional or pooled cross-sectional studies and four longitudinal studies. For prevalent hypertension, the pooled estimate for exclusive e-cigarette use included the null (OR 1.09, 95% CI 0.88-1.36; I² = 68.1%), whereas dual use was associated with higher odds of hypertension (OR 1.41, 95% CI 1.16-1.72; I² = 80.9%). Three non-overlapping longitudinal cohorts contributed to the primary incident analyses, with reported follow-up ranging from 3.7 to 6.0 years. For incident hypertension, the estimate for exclusive e-cigarette use also included the null (HR 1.17, 95% CI 0.83-1.64; I² = 64.3%), whereas dual use was associated with a higher risk of incident hypertension (HR 1.35, 95% CI 1.03-1.76; I² = 77.3%). In separate secondary analyses, cigarette-only smoking was associated with prevalent hypertension (OR 1.25, 95% CI 1.10-1.41) and incident hypertension (HR 1.20, 95% CI 1.15-1.25). Certainty of evidence was very low because of risk of bias, heterogeneity, and imprecision. Conclusions: No statistically clear association was observed between exclusive e-cigarette use and prevalent or incident hypertension; however, the very low-certainty and imprecise evidence does not exclude a potentially important association. Dual use was associated with higher odds of prevalent hypertension and a higher risk of incident hypertension, although causal interpretation is limited by observational study designs, heterogeneity, residual confounding, and exposure misclassification.