E-cigarette switching in COPD: reduced cardiovascular events without improvement in respiratory outcomes

The impact of switching to e-cigarettes in smokers after a chronic obstructive pulmonary disease (COPD) diagnosis on long-term health outcomes has not been widely evaluated. This nationwide cohort included 23,262 adults aged 40–80 years who were current smokers at the time of COPD diagnosis between 2016 and 2023. Based on follow-up health screening data, patients were categorized as continued smokers, quitters, or e-cigarette users (including dual users). The outcomes included lung cancer, COPD exacerbations, major adverse cardiac and cerebrovascular events (MACCE), and all-cause mortality. Adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs) were estimated using Cox proportional hazards model. Among 23,262 patients with COPD, 14,899 (64.0%) continued smoking, 7,047 (30.3%) quit, and 1,316 (5.7%) switched to e-cigarettes. During follow-up, quitters had significantly lower risks of lung cancer (adjusted HR [aHR], 0.85; 95% CI, 0.72–0.99), COPD exacerbations (aHR, 0.90; 95% CI, 0.84–0.97), MACCE (aHR, 0.85; 95% CI, 0.79–0.93), and all-cause mortality (aHR, 0.90; 95% CI, 0.82–0.99) compared with continued smokers. Switching to e-cigarettes was not associated with a lower risk of lung cancer (aHR, 0.94; 95% CI, 0.65–1.37) or COPD exacerbations (aHR, 0.98; 95% CI, 0.84–1.14) but was associated with a reduced risk of MACCE (aHR, 0.80; 95% CI, 0.66–0.97). Complete smoking cessation was associated with lower risks of lung cancer, COPD exacerbations, MACCE, and all-cause mortality. In contrast, switching to e-cigarettes was associated with a reduced risk of MACCE but did not provide comparable respiratory benefits.