Switching from cigarettes to IQOS: the relative importance of IQOS-associated reward, reinforcement and abstinence relief.

Introduction: This study investigated whether IQOS, a heated tobacco product, can fully substitute for combustible cigarettes and the factors that promote substitution.

Methods: Adults who smoked cigarettes daily (N=90; 21-65 years) completed a baseline ad-lib smoking period (days 1-5), two laboratory visits (days 6-7) and a 2-week period where they were instructed to switch from smoking cigarettes to using IQOS 3.0 (days 8-21). Mixed-effect modelling estimated the changes in cigarettes per day (CPD) and the percentage of baseline CPD substituted by HeatSticks during the switch period. Predictors included IQOS-associated subjective reward, relative reinforcing value, craving relief and withdrawal relief.

Results: Participants reduced their CPD to about 30% of their baseline smoking rate by the end of the 14-day switch period (p<0001). A lower versus higher reinforcing value of smoking relative to IQOS (RRV; break point <5 vs ≥5) predicted greater reductions in CPD (β=-1.31 (95% CI -2.35 to -0.27) p=0.013). Initially, IQOS use was 72% of the baseline smoking rate (β=71.64 (95% CI 42.79 to 100.48) p<0.0001) and climbed by 0.8% per day (β=0.82 (95% CI 0.01 to 1.64) p=0.05), for an average substitution rate of 83%. The subjective reward of IQOS was the only predictor of a higher substitution rate (β=4.26 (95% CI 1.03 to 7.50) p=0.01).

Conclusions: IQOS fully substituted for cigarettes in ~20% of people who were not immediately interested in quitting smoking while the remainder significantly reduced their smoking. Positive reinforcing effects of IQOS foster use and the transition away from combustible cigarettes.

Trial registration number: NCT05076708.