Adverse symptoms attributed to e-cigarettes over 6 months among participants of a randomized controlled trial testing nicotine free-base e-cigarettes for smoking cessation: secondary analysis of the ESTxENDS trial.

introductionPeople smoking tobacco cigarettes and switching to e-cigarettes report adverse symptoms attributed to e-cigarettes. We aimed at assessing the proportions and changes over 6 months in self-reported symptoms among participants of a large randomized controlled trial testing e-cigarettes for smoking cessation.

methodWe included participants from the intervention group of the Efficacy, Safety and Toxicology of ENDS (ESTxENDS) randomized controlled trial. They received e-cigarettes, freebase nicotine e-liquids and smoking cessation counseling, phone follow-up at 1-, 2-, 4-, 8-week, and a visit at 6 months after target quit date. A set of predefined adverse symptoms experienced while vaping or smoking were systematically assessed at each contact. We used descriptive statistics and mixed models to report proportion of symptoms over time in exclusive e-cigarette users. We assessed the effect of symptoms on smoking re-initiation and the effect of duration of exclusive e-cigarette use on the resolution of symptoms in marginal structural models.

resultsThe intervention group included 622 participants, with a mean age of 40 (SD: 14) and 53% identified as men. After 1 week, the most commonly reported adverse symptoms among the 405 exclusive e-cigarette users were dry mouth (34%, 95 CI: 29%-39%), mouth/throat irritation (23%, 19%-27%), and cough (25%, 21%-29%). After 6 months, 256 exclusive e-cigarette users reported dry mouth (18%, 14%-23%), mouth/throat irritation (11%, 7%-15%), and cough (12%, 8%-16%). Marginal structural model revealed mouth/throat irritation led to smoking re-initiation, but continuing exclusive e-cigarette use resolved dry mouth in many.

conclusionsAdverse symptoms attributed to e-cigarettes are reported by fewer exclusive e-cigarette users over time. While continued e-cigarette use led to less dry mouth, mouth/throat irritation symptoms seemed to resolve because people experiencing symptoms switched back to smoking tobacco, while continuous exclusive e-cigarette users had less symptoms. IMPLICATIONS: E-cigarette use for smoking cessation can lead to adverse symptoms, such as dry mouth, mouth/throat irritation, and cough. The proportion of these symptoms, especially of dry mouth, was lower in participants still exclusively using e-cigarettes after 6 months than in people after one week of use. These findings are crucial for health care professionals who recommend e-cigarettes for smoking cessation, as they offer practical guidance on how to inform their patients about the possibility of these symptoms when shifting to e-cigarettes.