Introduction: Understanding the relationship between ENDS use and chronic obstructive pulmonary disease and other respiratory conditions is critical. However, most previous studies have not fully adjusted for cigarette smoking history.

Methods: Using Waves 1-5 of the U.S. Population Assessment of Tobacco and Health study, the association between ENDS use and self-reported incident chronic obstructive pulmonary disease was examined among adults aged 40+ years using discrete-time survival models. Current ENDS use was measured as a time-varying covariate, lagged by 1 wave, defined as established daily or some days of use. Multivariable models were adjusted for baseline demographics (age, sex, race/ethnicity, education), health characteristics (asthma, obesity, exposure to second-hand smoke), and smoking history (smoking status and cigarette pack years). Data were collected between 2013 and 2019, and the analysis was conducted in 2021-2022.

Results: Incident chronic obstructive pulmonary disease was self-reported by 925 respondents during the 5-year follow-up. Before adjusting for other covariates, time-varying ENDS use appeared to double chronic obstructive pulmonary disease incidence risk (hazard ratio=1.98, 95% CI=1.44, 2.74). However, ENDS use was no longer associated with chronic obstructive pulmonary disease (adjusted hazard ratio=1.10, 95% CI=0.78, 1.57) after adjusting for current cigarette smoking and cigarette pack years.

Conclusions: ENDS use did not significantly increase the risk of self-reported incident chronic obstructive pulmonary disease over a 5-year period once current smoking status and cigarette pack years were included. Cigarette pack years, by contrast, remained associated with a net increase in chronic obstructive pulmonary disease incidence risk. These findings highlight the importance of using prospective longitudinal data and adequately controlling for cigarette smoking history to assess the independent health effects of ENDS.