E-cigarette use is associated with pulmonary inflammation, functional respiratory changes, and chronic lung disease. Most population-level E-cigarette research has utilized point-in-time measures of E-cigarette exposures, which may not generalize to adults who transition between cigarettes and E-cigarettes.

Data obtained from the Population Assessment of Tobacco and Health study were collected from 2013 to 2019 and analyzed in 2022. Three observations were created per respondent, with exposure intervals assessed over Waves 1–2, 2–3, and 3–4. Each wave of the exposure interval was classified as nonuse, exclusive E-cigarette use, exclusive smoking, or dual use, producing 16 possible cigarette‒E-cigarette transitions. The association between transitions and both dry nighttime cough and wheeze symptom development during follow-up were assessed using mixed-effects Poisson models.

Among 33,231 observations from 13,528 unique participants, transitioning from nonuse to exclusive E-cigarette use was associated with 1.62 times higher incidence rate of wheeze (incident rate ratio=1.62; 95% CI=1.12, 2.34) than persistent nonuse. There was no change in reported dry nighttime cough (incident rate ratio=0.84; 95% CI=0.52, 1.35) or wheeze (incident rate ratio=0.87; 95% CI=0.52, 1.46) in individuals who switched from cigarettes to E-cigarettes, whereas transitioning from dual use to E-cigarette use was associated with large reductions in both symptoms (incident rate ratio=0.58; 95% CI=0.39, 0.87 and incident rate ratio=0.36; 95% CI=0.20, 0.63, respectively).

E-cigarette initiation among nonusers is associated with increased respiratory morbidity. Further research should assess the risks and benefits of E-cigarette‒assisted cigarette cessation given the reduction in symptom development rates among dual use to E-cigarette switchers.