Nicotine and tobacco transitions among US youth using electronic nicotine delivery systems (ENDS): Associations with frequency, nicotine dependence, and biomarkers of exposure

INTRODUCTION: Vaping nicotine is the most prevalent mode of nicotine use among US youth. Research is needed to understand youth use over time, including transitions to or away from dual use. How these transitions are related to frequency of use, nicotine dependence, and biomarkers of nicotine and tobacco toxicant exposure provides key information on the public health impact of ENDS use among US youth. METHODS: Longitudinal data from Waves 4 and 5 (2016/18 - 2018/19) of the Wave 4 Biomarker Core sample (ages 12-17 at Wave 4) of the Population Assessment of Tobacco and Health (PATH) Study were used. Eight Wave 4 to 5 transitions in ENDS and combustible tobacco use were examined among youth reporting current ENDS use at Wave 4 (n=419). Past 30-day ENDS use frequency, nicotine dependence, and biomarkers of nicotine and tobacco toxicant exposure at Wave 4 and Wave 5 were compared across transition groups. RESULTS: Youth who maintained dual use and youth who transitioned from dual use to ENDS-only use reported the highest estimated days of ENDS use (M=22.12 days and 23.86 days, respectively) and the highest mean nicotine dependence (M=2.75 and 2.74, respectively). Those who maintained dual use had significantly greater increases in nicotine exposure (GMR=3.87; 95% CI=1.67, 8.98) and tobacco-specific nitrosamine exposure (GMR=3.53; 95% CI=2.19, 5.70) compared to youth who maintained ENDS-only use. CONCLUSIONS: We found significant heterogeneity by transition group among US youth using ENDS. Dual use, particularly persistent dual use, represents a significant concern for the health of youth.