Harm Reduction Associated with Dual Use of Cigarettes and e-Cigarettes in Black and Latino Smokers: Secondary Analyses from a Randomized Controlled e-Cigarette Switching Trial

Introduction: Most adult cigarette smokers who use e-cigarettes are dual cigarette and e-cigarette (CC-EC) users, yet little is known about relative consumption of cigarettes to e-cigarettes and any associated harm reduction. Methods: Rate of substitution from cigarettes to e-cigarettes at week 6 and change in biomarkers of exposure and potential harm were examined among dual dual cigarette and e-cigarette users [64/114 (56%); 35 Black, 29 Latino] in an e-cigarette switching randomized trial. Results: Dual users averaged 79% substitution of cigarettes for e-cigarettes at week 6, resulting in a reduction from baseline of 70.0 +/- 54.1 cigarettes per week (p < .001).Total nicotine consumption remained stable (baseline: 1160.5 +/- 1042.1 pg/mL of cotinine, week 6: 1312.5 +/- 1725.9 pg/ mL of cotinine, p = .47), while significant reductions were seen in the potent lung carcinogen 4-(methylnitrosamino)-1-(3-pyridul)-1-butanol (NNAL) (-55.9 t 88.6 ng/ml, p < .001), carbon monoxide (-6.3 +/- 8.6 ppm, p < .001), and self-reported respiratory symptoms (-3.3 +/- 8.0, p= .002). No significant changes were found in blood pressure or spirometry. Greater substitution from cigarettes to e-cigarettes was associated with larger reductions in NNAL (r= -.29, p= .02). Conclusions: The predominant dual-use pattern was characterized by regular e-cigarette and intermittent cigarette use. Findings demonstrate the short-term harm reduction potential of this dual-use pattern in Black and Latino smokers and suggest that the greatest benefit, aside from cessation of both products, is achieved by higher substitution of e-cigarettes for cigarettes. Findings need confirmation in a larger sample with longer follow-up in dual users with greater variability in the rate of substitution.