E-cigarette Duration and Incident COPD Among Adults Aged 40 Years and Older with a Smoking History

ImportanceChronic obstructive pulmonary disease (COPD) remains a leading cause of morbidity and mortality in the United States (US), largely driven by cigarette smoking and characterized by progressive lung injury. While e-cigarettes are promoted as a less harmful alternative to cigarette smoking, their long-term health effects, including the impact of prolonged use on COPD incidence among adults who have smoked, are not well understood. ObjectiveTo evaluate the prospective association between duration of e-cigarette use and incident COPD among US adults aged 40 years or older with a history of cigarette smoking, and to determine whether baseline respiratory symptoms modify this association. Design, Settings, and ParticipantsWe used data from Waves 4 to 7 (2017-2022) of the Population Assessment of Tobacco and Health (PATH) Study, a nationally representative US longitudinal cohort study. Our analysis included adults aged 40 years or older who currently or formerly smoked cigarettes. Main Outcomes and MeasuresThe outcome was incident, self-reported COPD diagnosis. The main exposure was the time-varying duration of e-cigarette use. Baseline functionally important respiratory symptoms were defined by a validated index. Multivariable models adjusted for demographics, COPD risk factors, and detailed tobacco use history, including cigarette smoking status, time since quitting, and pack-years. ResultsAmong 4,895 adults aged 40 year or older who currently or formerly smoked cigarettes, 408 reported an incident COPD diagnosis. Among individuals with baseline respiratory symptoms, longer e-cigarette use duration was associated with increased COPD risk (adjusted hazard ratio [AHR]: 1.28, 95% CI: 1.16, 1.40), whereas no significant association was observed among those without baseline respiratory symptoms (AHR: 1.01, 95% CI: 0.92, 1.12). Results were consistent after adjusting for cumulative cigarette exposure and other risk factors and remained robust across multiple sensitivity analyses. Conclusion and RelevanceProlonged e-cigarette use may increase COPD risk among individuals with pre-existing respiratory vulnerabilities. Although switching from combustible cigarettes remains an important harm reduction strategy, behavioral counseling and pharmacotherapy should be prioritized for those at high risk for COPD, with e-cigarette cessation support available to high-risk former smokers. Continued surveillance and research are warranted as e-cigarette products and use patterns evolve. Key PointsO_ST_ABSQuestionC_ST_ABSDoes longer e-cigarette use increase COPD risk in adults with a smoking history? FindingsIn this national cohort study of U.S. adults aged 40+ who currently or formerly smoked, e-cigarette duration was associated with higher self-reported COPD incidence among individuals with respiratory symptoms at baseline (adjusted hazard ratio [AHR] 1.28, 95% CI 1.16, 1.40) but not among those without symptoms (AHR 1.01, 95% CI 0.92, 1.12). MeaningProlonged e-cigarette use may increase COPD risk among individuals with respiratory vulnerabilities. While cigarette cessation should remain the priority, evidence-based e-cigarette cessation strategies are needed to prevent long-term use in this population.