Abstract
INTRODUCTION: The pattern and trajectory of dual use are critical to differentiating it as a health benefit versus harm. METHODS: Based within a large, naturalistic randomized controlled trial of e-cigarette in the United States, adults who smoke were given a 1-month sample of tank-style e-cigarette to use as they wish (n = 427) or not (n = 211). Analyses are restricted to participants from the e-cigarette group who became dual users by one month (DU; n = 315) versus participants in control group who exclusively used combustible cigarettes (EUCC; n = 182). Primary outcomes are based on changes in combustible cigarette smoking (cigarettes per day; CPD) across daily diaries within sampling period, and at 3- and 6-month follow-up. RESULTS: DUs reported significantly more diary days of large smoking reduction (smoking 1-50% of baseline CPD: 23.1% of all diary days) and not smoking (5.6% of all diary days) than did EUCCs (6.8% and 1.4%, respectively) during sampling period (ps < .001). Among DUs, 18.4% reported smoking 1-50% of baseline CPD and 9.5% were not smoking at Week 12; 17.5% reported smoking 1-50% of baseline CPD and 9.2% were not smoking at Week 24. In contrast, among EUCCs, 7.1% reported 1-50% of baseline CPD at Week 12 and 1.7% were not smoking. At Week 24, 8.2% reported 1-50% of baseline CPD and 7.1% were not smoking. Among DUs, e-cigarette use days were associated with greater probability of non-smoking days (8%) than non-e-cigarette use days (3%, p < .001). CONCLUSION: Compared to continued cigarette smoking, initiating dual use reduced smoking and increased cigarette-free days.