Objective:

Electronic cigarettes (e-cigarettes) are often presented as a less harmful alternative to combustible cigarettes (hereinafter, cigarettes). This study updates an earlier meta-analysis of 107 population studies of e-cigarette disease risks.

Methods:

We pooled data from studies in PubMed, EMBASE, Web of Science, and PsychINFO from January 1, 2005, through January 1, 2025, in a random-effects meta-analysis if we identified ≥5 studies for a disease outcome.

Results:

We identified 142 odds ratios (ORs) (107 [75%] from cross-sectional studies and 35 [25%] from longitudinal studies) from 124 articles, including 18 new articles. Comparing e-cigarette use with cigarette use, the ORs (95% CIs) for metabolic dysfunction (1.00 [0.91-1.09]) and oral disease (0.89 [0.78-1.02]) were not different from 1.0. The ORs (95% CIs) for cardiovascular disease (0.76 [0.58-0.99]), stroke (0.62 [0.47-0.82]), asthma (0.84 [0.74-0.95]), chronic obstructive pulmonary disease (0.55 [0.40-0.76]), and fetal growth (0.64 [0.44-0.92]) were ≤1.0. Pooled ORs for dual use versus cigarette use were increased for all outcomes (range, 1.22-1.42) except fetal growth (0.99). Pooled ORs for e-cigarette use, compared with nonuse of e-cigarettes, were increased for all outcomes (e-cigarette range, 1.24-1.53) except fetal growth (1.20). Dual use was associated with increased ORs for all outcomes (1.49-3.17). Studies had a low risk of bias. Results were generally not sensitive to study characteristics. Confidence in conclusions was mostly moderate to high except for stroke, where confidence was low for some outcomes, and fetal growth, for which confidence was very low for all outcomes.

Conclusion:

The growing literature increases confidence that e-cigarette use is associated with disease outcomes indistinguishable from or approaching cigarette use, with dual use associated with higher ORs. E-cigarettes should not be promoted as a safer alternative to cigarettes.