Impact of electronic cigarette and heated tobacco product on conventional smoking: an Italian prospective cohort study conducted during the COVID-19 pandemic.

Objective: Debate continues about whether electronic cigarettes (e-cigarettes) and heated tobacco products (HTP) reduce or increase the probability of smoking, with many studies compromised by stated or unstated conflicts of interest. We undertook a longitudinal study in Italy.

Methods: 3185 Italian participants aged 18-74 years provided baseline (April-May) and follow-up (November-December) responses in 2020, reporting smoking status and use of e-cigarettes and HTP. We tracked transitions over that period and reported risk ratios (RR) and corresponding 95% CIs for changes in smoking in relation to baseline use of e-cigarettes and HTPs.

Results: Never cigarette smokers who used e-cigarettes at baseline were much more likely to start smoking (compared with never users, RR 8.78; 95% CI: 5.65 to 13.65) and current HTP users (RR 5.80; 95% CI: 3.65 to 9.20). Among ex-smokers, relapse (17.2%) at follow-up was more likely among e-cigarette (RR 4.25; 95% CI: 2.40 to 7.52) and HTP users (RR 3.32; 95% CI: 2.05 to 5.37). Among current smokers at baseline, those who had continued smoking at follow-up were 85.4% overall. These were more frequently current novel product users (compared with non-users, RR 1.10; 95% CI: 1.02 to 1.19 for e-cigarette users; RR 1.17; 95% CI: 1.10 to 1.23 for HTP users).

Conclusions: Both e-cigarette and HTP use predict starting smoking and relapse, and appear to reduce smoking cessation. Due to the limited sample size within specific strata, the association with quitting smoking should be confirmed by larger prospective studies. These findings do not support the use of e-cigarettes and HTPs in tobacco control as a consumer product, at least in Italy.