Associations between dual use of e-cigarettes and smoking cessation: a prospective study of smokers in England.

BACKGROUND: It has been claimed that use of e-cigarettes in combination with cigarettes outside of a quit attempt ('dual use') reduces quitting among smokers. This study aimed to assess whether dual e-cigarette users have lower smoking cessation rates than (i) exclusive cigarette smokers or (ii) dual users of nicotine replacement therapy (NRT) and cigarettes. METHODS: Prospective cohort study of 1,498 smokers in England. The independent variable was dual use of e-cigarettes (n = 292), dual use of NRT (n = 117), or exclusive smoking (n = 1089), assessed at baseline. Outcomes were overall quit rate, past-year quit attempts, and success of quit attempts at 12-month follow-up. Baseline sociodemographic and smoking-related covariates were included. RESULTS: Overall quit rates were not lower in dual e-cigarette users than exclusive smokers (OR = 1.31, 0.90-1.89). Dual users of e-cigarettes were more likely than exclusive smokers to make a quit attempt, but this difference was not significant after adjustment for covariates (OR = 1.27, 95%CI 0.95-1.69). Among those attempting to quit, success rates did not differ significantly. Dual users of e-cigarettes were less likely to make a quit attempt than dual users of NRT (OR = 0.61, 95%CI 0.38-0.98) but the success rate of quit attempts and overall quit rates did not differ significantly. CONCLUSIONS: In England, dual use of e-cigarettes is not associated with reduced overall quit rates compared with exclusive smoking or dual use of NRT. However, dual use of e-cigarettes is associated with a slightly higher quit attempt rate than exclusive smoking but lower than dual use of NRT