The Risks of Mortality, Cardiovascular Events, and Pulmonary Complications in Cancer Patients Who Smoke Cigarettes and Switch to E-Cigarettes: South Korea, 2015‒2022.

Abstract

<b>Objectives.</b> To evaluate the risks of mortality, cardiovascular events, and pulmonary complications among cancer patients who quit, continued smoking, or switched to e-cigarettes after diagnosis. <b>Methods.</b> Using the Korean National Health Insurance Service database (2015-2022), we identified 46 834 cancer patients who were smoking at diagnosis. Patients were categorized as continued smokers (n = 17 418), quitters (n = 25 909), or e-cigarette users (n = 3507) after diagnosis. We used multivariable Cox proportional hazards models to assess associations. <b>Results.</b> During a median 4.2 years of follow-up, all-cause mortality was significantly lower in quitters (hazard ratio [HR] = 0.92; 95% confidence interval [CI] = 0.86, 0.98) and e-cigarette users (HR = 0.84; 95% CI = 0.72, 0.99) than continued smokers. Both groups also showed lower cardiovascular event risks (HR = 0.64; 95% CI = 0.57, 0.72 and HR = 0.72; 95% CI = 0.53, 0.97, respectively). Compared with quitters, e-cigarette users had increased pulmonary complication risk (HR = 1.26; 95% CI = 1.00, 1.58). <b>Conclusions.</b> E-cigarette use was associated with lower mortality and cardiovascular risks than continued smoking, though complete cessation conferred greater benefits. Elevated pulmonary complications in e-cigarette users warrant caution. (<i>Am J Public Health</i>. Published online ahead of print July 2, 2026:e1-e12. https://doi.org/10.2105/AJPH.2026.308512).