Moderators of the impact of e-cigarette provision on smoking cessation: secondary analyses from a large naturalistic randomized clinical trial in the US

BACKGROUND AND AIMS: Growing evidence suggests that e-cigarettes can facilitate smoking cessation among adults who smoke (AWS). Whether these effects differ by characteristics of individuals with varying demographic or smoking related histories is unclear. This study uses data from a recently completed RCT testing e-cigarette sampling among AWS to evaluate moderators of smoking behavior outcomes. METHODS: Analyses are based on a large, naturalistic RCT conducted across the US, in which AWS (N = 638) were randomized (2:1) to receive a 4-week supply of e-cigarettes, or not. Provision of e-cigarettes included minimal guidance on use and emphasized participants' self-determined decisions and patterns of use. Outcomes were tracked through week 24 follow-up. Secondary analyses focus on group-by-moderator (demographic, smoking history) interactions on three principal outcomes: 1) incidence of 24hr quit attempts, 2) incidence of reducing smoking (cigarettes per day; CPD) by ≥ 50%, and 3) 7-day point prevalence abstinence (PPA), each captured at week 4 and week 24. RESULTS: Among 10 + demographic and smoking history variables assessed at baseline, none of the group by moderator interactions were significant, for any outcome at either timepoint. Raw cessation outcomes were higher among AWS with higher motivation to quit (MTQ), but the relative risk (RR) for achieving ≥ 50% reduction in CPD after 4 weeks was similar across MTQ levels. DISCUSSION AND CONCLUSIONS: The effects of e-cigarettes on smoking cessation outcomes were similar across multiple demographic and smoking history subgroups. The absence of any significant moderating variables is unlikely attributable to limited power since the vast majority of subgroup differences were < 10%.