Continuous associations of the brief Wisconsin Inventory of Smoking Dependence Motives with transitions between cigarette and e-cigarette use

INTRODUCTION: Measures of cigarette and e-cigarette dependence may predict product transitions, and they could be used to inform tailored messaging for cigarette cessation. METHODS: We used data from a longitudinal cohort study of 353 adults who smoked cigarettes daily, with or without e-cigarettes, with product dependence assessed at baseline and year one and follow-up visits every two months (enrolled 2015-17 in Madison and Milwaukee, WI). We estimated continuous, non-linear associations between the brief Wisconsin Inventory of Smoking Dependence Motives scores for cigarettes (WISDM) and e-cigarettes (e-WISDM) with transition rates using a multistate transition model. RESULTS: Lower WISDM scores were associated with lower rates of transitioning from cigarette-only to dual use; only 3.5% (95% CI: 1.4%, 9.3%) of those at the 10th WISDM percentile were predicted to transition to dual use compared with 25.0% (95% CI: 14.0%, 39.1%) at the 50th percentile. Higher e-WISDM scores were associated with lower rate of transitioning from dual use to either cigarette-only or e-cigarette-only use, with 50.7% (95% CI: 31.9%, 65.7%) of those who used both products predicted to continue to do so at the 50th percentile of e-WISDM compared with 91.1% (95% CI: 78.7%, 96.1%) predicted to continue both products at the 90th percentile. Ratios of e-WISDM:WISDM above 1 were associated with an increased likelihood of transitioning from dual to e-cigarette-only rather than cigarette-only use. CONCLUSIONS: Product dependence scores were non-linearly associated with transition rates between cigarette and e-cigarette use, which may help to guide the development of personalized, adaptive cigarette cessation recommendations.