Transitions from Exclusive Cigarette Smoking to Dual or Exclusive ENDS Use: Changes in Nicotine Dependence and Use...

Electronic nicotine delivery systems (ENDS) can aid cigarette cessation in trials; however, in real-world cohorts, dual use is more common than switching to exclusive ENDS, raising questions about harm-reduction potential. We examined changes in Tobacco Dependence Index (TDI), smoking behavior, and ENDS use among exclusive smokers who transitioned to dual or exclusive ENDS use.

Adults in the Population Assessment of Tobacco and Health Study (Waves 1-7) contributed adjacent wave-pair episodes (baseline and follow-up). Outcomes included change in TDI (defined as the maximum of the cigarette- or ENDS-TDI for dual users), follow-up cigarette- and ENDS-TDI, non-daily smoking, ≥50% cigarettes-per-day (CPD) reduction, daily ENDS use, and pickups/day and puffs/pickup. Weighted generalized estimating equations adjusted for baseline TDI, wave, and demographics.

Relative to remaining smokers, adjusted change in overall TDI was -6.26 for dual users and -10.81 for exclusive ENDS switchers (both p < .0001). Reductions in cigarette-TDI were small and nonsignificant for dual users (-1.72) but substantially larger for exclusive ENDS switchers (-33.90). However, dual users were more likely than remaining smokers to become non-daily smokers (RR 3.85) and achieve a ≥50% CPD reduction (RR 2.65). At follow-up, exclusive ENDS switchers scored higher on ENDS-TDI (+18.49 points) but lower on cigarette-TDI (-33.97 points) than dual users, alongside higher daily ENDS use (RR 2.08) and pickups/day (IRR 1.47), with similar puffs/pickup.

Exclusive ENDS switchers reported the largest dependence reductions, whereas dual users showed moderate overall reductions but little change in cigarette dependence, consistent with a behavioral pattern of supplementation.