Functionally important respiratory symptoms and continued cigarette use versus e-cigarette switching: population assessment of tobacco and health study waves 2-6.

Background: Substitution of noncombustible tobacco products for cigarettes could improve respiratory symptoms. We hypothesized that complete cigarette-to-e-cigarette switching would improve respiratory symptoms compared to continued smoking. Methods: Longitudinal analysis of data from waves 2-6 (W2-W6; 2014-2021) of the Population Assessment of Tobacco and Health (PATH) Study, an observational cohort study that surveyed 5653 US adults ≥18 years without COPD/chronic bronchitis/emphysema. We compiled 14,947 two-wave (1-2 year) observations with persons who smoked cigarettes at baseline and compared the relation between functionally important respiratory symptoms and switching to exclusive e-cigarette use or quitting tobacco versus continued cigarette use (reference). A 9-point wheezing/nighttime cough index was dichotomized based on index scores of ≥2 or ≥3, previously associated with poorer functional health. Multivariable models assessed how changes in cigarette use predicted worsening/improvement of symptoms. Findings: Among those with an index score <2, 3.5% switched to e-cigarettes, and 11.1% quit all tobacco. Functionally important respiratory symptoms worsened (≥2 at follow-up) in 15.4%, 10.0% and 10.1% of those who continued cigarettes, switched to e-cigarettes, and quit, respectively. Adjusted relative risk (RR) for respiratory symptom worsening was 0.69 (95% confidence interval (CI), 0.52, 0.91) for e-cigarette switching and 0.73 (95% CI, 0.54, 0.97) for quitting. Of persons with index score ≥2, 2.8% switched to e-cigarettes, and 6.7% quit. Respiratory symptoms improved (<2 at follow-up) in 27.7%, 45.8% and 42.1% of those who continued cigarettes, switched to e-cigarettes, and quit, respectively. The RR for improving was 1.31 (95% CI, 1.05, 1.64) for e-cigarette switching and 1.36 (95% CI, 1.15, 1.62) for quitting. The RRs for exclusive e-cigarette use with a cutoff of ≥3 for respiratory symptom worsening and improvement were not significant (0.74 [0.53, 1.05] and 1.20 [0.95, 1.51] respectively) but were significant in an unweighted analysis that included partial data for individuals lost to follow-up (0.74 [0.57, 0.95] and 1.21 [1.06, 1.39] respectively). Interpretation: Switching completely from past 30-day use of cigarettes to e-cigarettes had short-term beneficial associations with functionally important respiratory symptoms similar to quitting tobacco completely. Funding: This manuscript is supported with Federal funds from the National Institute on Drug Abuse (NIDA) at the National Institutes of Health (NIH), and the Center for Tobacco Products (CTP) at the Food and Drug Administration (FDA), Department of Health and Human Services, under contract to Westat (contract nos. HHSN271201100027C and HHSN271201600001C), and through an interagency agreement between NIH NIDA and FDA CTP. Heather L. Kimmel was substantially involved in the scientific management of and providing scientific expertise for contract nos. HHSN271201100027C and HHSN271201600001C.