Dual Users Compared to Smokers: Demographics, Dependence, and Biomarkers.

Introduction The availability of e-cigarettes has profoundly changed the tobacco product landscape. In the US, almost 6 million adults use both combustible and electronic cigarettes (i.e., dual users). The goal of this study is to understand how smokers and dual users differ in terms of demographics, cigarette dependence, and exposure to carcinogens. Methods An observational cohort (smokers, n=166, ≥5 cigarettes/day for 6 months and no e-cigarette use in 3 months; dual users, n=256, smoked daily for 3 months and used e-cigarettes at least once/week for the past 3 months) completed baseline assessments of demographics, tobacco use, and dependence. They also provided breath samples for carbon monoxide (CO) assay and urine samples for cotinine, 3-hydroxycotinine (3HC), and 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) assays. Results Compared to smokers, dual users (mean e-cigarette use=5.5 days/week [SD=1.9]) were significantly younger and more likely to be white, have more education, report a history of psychiatric co-morbidity, and smoke fewer cigarettes/day. There were no differences in CO, cotinine, or 3HC levels; however, dual users had significantly lower levels of NNAL than did smokers. Most smokers and dual users had no plans to quit smoking within the next year; 91% of dual users planned to continue using ECs for at least the next year. Conclusions In this community sample, dual users are supplementing their smoking with e-cigarette use. Dual users, versus smokers, smoked fewer cigarettes per day and delayed their first cigarette of the day, but did not differ in quitting intentions. Implications This comparison of a community sample of established dual users and exclusive smokers addresses key questions of dependence and health risks of dual use in real-world settings. Dual users were more likely to be white, younger, have more than a high school education and have a psychiatric history. Dual users also smoked significantly fewer cigarettes and had lower levels of NNAL (a carcinogen), but they did not differ from exclusive smokers in carbon monoxide or cotinine levels, suggesting that they supplemented their nicotine intake via e-cigarettes.