ENDS use and nicotine exposure among adults who use ENDS alone or with cigarettes: The PATH Study 2013-2019.

Abstract

Introduction: Evaluating nicotine exposure (total nicotine equivalents-2; TNE-2) changes over time can provide data on the public health impact of electronic nicotine delivery systems (ENDS). This study describes TNE-2 levels of those who use ENDS with or without cigarettes from 2013-2019, and models how changing ENDS use behavior impacts change in TNE-2.

Methods: Creatinine-corrected TNE-2 was assessed for exclusive ENDS use and dual ENDS and cigarette use from Waves (W) 1-5 of the Population Assessment of Tobacco and Health Study. Exploratory analyses using generalized estimated equations modeled how changing ENDS use (i.e., frequency of use, flavor use, device type) between wave pairs (W1-W2, W2-W3, etc.) impacted changes in TNE-2.

Results: For exclusive ENDS use at each wave, TNE-2 levels increased from 10.1 µmol/g at W1 to 18.4 µmol/g at W5, a positive linear trend (p=0.03). Among those who exclusively used ENDS at all waves, TNE-2 levels peaked at W3 and then decreased at W5, exhibiting a significant quadratic trend (p=0.02). Switching from non-daily to daily use (n=15) was associated with a greater increase in TNE-2 than continued daily use (n=304). For dual use, TNE-2 levels remained relatively flat, and there were no significant effects of changing ENDS behavior on TNE-2.

Conclusions: For exclusive ENDS use, TNE-2 levels over time differs when looking within-subjects vs. repeated longitudinal assessments, and frequency of use was the only significant predictor of change in TNE-2. TNE-2 from dual use did not significantly change from 2013-2019 and was not impacted by change in ENDS use behavior.

Implications: Exclusive ENDS use was associated with a positive linear trend in nicotine exposure between 2013-2019, which may reflect how newer generations of ENDS are better at delivering nicotine. When limiting analysis to within-subject use at all waves the trend was quadratic, with nicotine exposure peaking at W3 and returning toward W1 levels by W5. This may be related to people trying to titrate their nicotine exposure in response to changes in ENDS characteristics. Dual ENDS and cigarette use had more consistent levels of exposure over time, which could be due to greater ease of nicotine titration via cigarettes.