Abstract Introduction To examine the relationship between early product substitution and harm reduction (HR) in an ENDS switching trial for adults who smoke. Methods We conducted a longitudinal structural equation analysis of 120 treatment participants who received disposable ENDS for 8 weeks and were assessed every 2weeks. The predictor was w2 ENDS sessions/day. The HR latent construct included 4 binary indicators: cigarettes/day (CPD) ≤5 and carbon monoxide (CO) 10ppm at weeks 6 0.001), mediated through reductions in w2 CPD. The ENDS direct pathway was moderated by w0 CPD (p0.001). For the total (direct + indirect) association, greater w2 ENDS use increased chances of HR for individuals with w0 CPD16, decreased the chances of HR for individuals with w0 CPD7 and had no impact on those in the w0 CPD 7-15. All predictors combined explained 66% of the variance in HR. Conclusions In this study, early ENDS use predicted short-term HR, but only for individuals who smoked more heavily. For those with low smoking intensity, early ENDS use predicted decreased short-term chances of HR and increased dual product use. This is a novel finding limited to a small sample of persons with severe mental illness. Implications If replicated and extended to later HR outcomes, the finding supports a focus on early ENDS use as an intermediate outcome for phase 2 trials of ENDS products, and adaptive treatment designs aimed at early non responders, with a particular focus on persons who smoke heavily.
Stoolmiller et al. (Wed,) studied this question.