Concurrent E-cigarette Use While Enrolled in a Smoking Cessation Program: Associations Between Frequency of Use, Motives for Use, and Smoking Cessation

Introduction: Trial evidence suggest that e-cigarettes may aid in quitting smoking, while observational studies have found conflicting results. However, many observational studies have not adjusted for important differences between e-cigarette users and non-users. Methods: We aimed to determine the association between e-cigarette use frequency and motivation to use e-cigarettes to quit smoking, and smoking cessation using data from Canada's largest smoking cessation program. Participants who completed a baseline assessment and 6-month follow-up questionnaire were divided post hoc into 4 groups based on their self-reported e-cigarette use during the 30 days before baseline: 1) non-users; 2) users of e-cigarettes not containing nicotine; 3) occasional users; and 4) frequent users. Occasional and frequent users were further divided into two groups based on whether they reported using e-cigarettes to quit smoking. Abstinence at 6-month follow-up (7-day point prevalence abstinence) was compared among groups. Results: Adjusted quit probabilities were significantly higher (both p<0.001) for frequent baseline e-cigarette users (31.6%; 95% CI = 29.3%, 33.8%) than for non-users (25.8%; 25.3%, 26.3%) or occasional users (24.2%; 22.5%, 26.0%). Unadjusted proportions favoured non-users over occasional users (p<0.001), but this was not significant after adjustment (p=0.06). People using e-cigarettes to quit smoking were not likelier than other users to be successful, but were likelier to report frequent e-cigarette use during follow-up. Conclusions: Frequent baseline e-cigarette use predicted successful smoking cessation, compared to occasional and non-users. Use of e-cigarettes to quit did not predict smoking cessation, but was associated with continued use during follow-up, perhaps due in part to planned transitions to e-cigarettes.