E-liquid flavors and nicotine concentration choices over 6 months after a smoking cessation attempt with ENDS: Secondary analyses of a randomized controlled trial

Introduction: Many tobacco smokers try to quit with electronic nicotine delivery systems (ENDS or e-cigarettes). We aimed to describe e-liquid flavors and nicotine concentration use over 6 months in a prospective cohort of smokers willing to quit with ENDS. Methods: We included 622 participants from the intervention group of the Efficacy, Safety and Toxicology of ENDS randomized controlled trial. Participants were adult smokers smoking at least five cigarettes a day. They received free ENDS and a choice of 6 e-liquid flavors in 4 nicotine concentrations and smoking cessation counseling. We tracked flavor choice and nicotine concentration at 1, 2, 4, and 8 weeks, and at 6 months, after the target quit date, comparing participants who reported only vaping (exclusive e-cigarette users) to those who vaped and smoked (dual users) over the last 7 days. We applied multivariable regression models to compute adjusted risk ratios (ARR). Results: At Week 1, 66% (n=409) were exclusive e-cigarette users, and 21% (n=129) were dual users. At Month 6, 43% (n=266) were exclusive e-cigarette users, and 16% (n=102) were dual users. While flavor choices were similar at Week 1, at 6 months, exclusive e-cigarette users reported using more fruity flavors than dual users (31% vs 22%, ARR=2.10; 95% CI: 1.21-3.66). The nicotine concentration used initially was similar in both groups and diminished over time. At 6 months, exclusive e-cigarette users used a lower mean nicotine concentration than dual users (6.3 vs 8.2 mg/mL, difference= -1.55; 95% CI: -2.84 - -0.25 mg/mL). Conclusions: After 6 months, exclusive e-cigarette users used more fruity-flavored e-liquids and chose a lower mean nicotine concentration than dual users.