Respiratory Health Consequences Of Vaping In Healthy Adults: A Systematic Review

Abstract

Background: Electronic cigarettes are widely promoted as a reduced-harm alternative to combustible tobacco, yet whether their aerosol is respiratorily safe for healthy adults particularly those who have never smoked—remains contested. Existing syntheses largely pool clinically heterogeneous populations, obscuring the effect attributable to vaping itself. This review synthesises the respiratory health consequences of e-cigarette use specifically in healthy adults.

Methods: Following PRISMA 2020 guidelines, PubMed/MEDLINE was searched for original human studies published between January 2021 and July 2026 reporting respiratory symptoms, lung function, respiratory disease, or airway biomarkers in adults (≥18 years) without significant pre-existing respiratory disease. Screening, extraction, and risk-of-bias appraisal (Newcastle–Ottawa Scale and Joanna Briggs Institute checklists) were conducted by a single reviewer. Findings were synthesised narratively across four outcome domains.

Results: Thirty-four studies were included. Respiratory symptoms were the most consistently reported outcome; large, well-adjusted cohorts found elevated symptom risk among e-cigarette users that persisted in never-smokers (adjusted odds ratio for wheezing up to 1.51, 95% CI 1.06–2.14; adjusted asthma-symptom score ratio up to 1.44 in never-smokers). Conventional spirometry was frequently preserved, whereas more sensitive measures lung clearance index, cardiopulmonary exercise testing, exhaled nitric oxide, and exhaled lipid biomarkers detected subclinical peripheral-airway and inflammatory abnormalities in young, otherwise healthy vapers. Across domains, risk was greatest among dual users, while effects of exclusive e-cigarette use were smaller but frequently non-null. Studies reporting minimal effects were disproportionately affected by conflicts of interest.

Conclusions: In healthy adults, e-cigarette use is associated with increased respiratory symptoms and subclinical airway and inflammatory changes, even among never-smokers. Preserved spirometry appears to reflect the insensitivity of that measure rather than an absence of harm. The evidence does not support characterising vaping as respiratorily safe, though residual confounding by combustible tobacco, cross-sectional designs, and young-adult–dominated samples preclude firm causal conclusions. Large, prospective, independently funded cohorts using sensitive airway measures are needed.