The Role of Flavor in the Substitutability of E-cigarettes for Combustible Cigarettes Among Persistent Smokers

This between-subjects study aims to evaluate the effect of flavor on initial and sustained switching from combustible cigarettes to e-cigarettes among 210 cigarette smokers. After measuring baseline cigarette smoking rate, participants will be randomized to a six-week regimen of fruit-flavored, tobacco-flavored, or menthol-flavored e-cigarettes and be instructed to switch (versus smoking cigarettes) over a 6-week period. Flavor-associated subjective reward and the reinforcing value of flavored e-cigarettes relative to combustible cigarettes will be assessed as mechanisms.

The average smoker will attempt to quit smoking at least 30 times before abstaining for 12 months or longer. These attempts typically occur over decades of smoking, carcinogen and toxicant exposure, resulting in 480,000 deaths annually. As highlighted in the Surgeon General's Report, helping smokers who cannot quit smoking switch to less harmful non-combustible nicotine-containing products, such as e-cigarettes, has the potential to reduce this health burden dramatically. Substituting e-cigarettes for combustible cigarettes might only be possible for persistent smokers if e-cigarettes are accessible and appealing. Harm reduction proponents have advocated for the continued availability of e-cigarette flavors to appeal to and aid cigarette smokers unable to quit with traditional methods. Yet, there are no prospective studies of the effect of flavor on initial and sustained switching from combustible to electronic cigarettes. Converging laboratory, epidemiological, and clinical research suggests that fruit-flavored e-cigarettes with nicotine may be a viable substitute for combustible cigarettes among persistent smokers. The proposed study seeks to answer two novel questions relevant to public health and the regulation of e-cigarette flavoring. First, do persistent smokers substitute fruit-flavored e- cigarettes more readily than traditional-flavored e-cigarettes (tobacco or menthol) for combustible cigarettes? Second, are fruit-flavored e-cigarettes more rewarding and reinforcing than traditional-flavored e-cigarettes, and do these effects facilitate switching? The proposed research will fill these gaps in the evidence base by randomizing 210 persistent cigarette smokers to a six-week regimen of fruit-flavored (FF: watermelon and blueberry, n=70), tobacco-flavored (TF n=70) or menthol-flavored (MF n=70) e-cigarettes in a between-subjects design. Baseline smoking rate will be established during days 1-5. After biochemically verified overnight cigarette smoking abstinence, laboratory visits on days 6 and 7 will assess flavor-associated subjective reward and the reinforcing value of flavored e-cigarettes relative to combustible cigarettes. Participants will then switch from cigarette smoking to e-cigarette use for six weeks. Participants will collect spent cigarette filters daily to assess cigarettes smoked per day (cpd) if they smoke. The primary outcome measure is the longitudinal daily count of cigarettes from baseline to the end of the six-week switch period, with cigarettes per day at a 6-month follow-up as a secondary endpoint.