E-cigarettes and smoking cessation in the United States according to frequency of e-cigarette use and quitting duration: analysis of the 2016 and 2017 National Health Interview Surveys.

INTRODUCTION: The study purpose was to examine the association between electronic cigarette (e-cigarette) use and smoking cessation among United States (US) adults. Duration of smoking cessation was taken into consideration since e-cigarette awareness and use were low in the US before 2010.

METHODS: Pooled analysis of the 2016 and 2017 National Health Interview Surveys on current (N=9935) and former smokers (N=14754) was performed. Adjusted prevalence ratios (aPRs), adjusted for sociodemographic factors, were calculated.

FINDINGS: Current e-cigarette use was reported by 10.5% (95%CI:9.8-11.3%) of current smokers and 4.5% (95%CI:4.0-5.0%) of former smokers. Prevalence was high in former smokers of <1 year (16.8%, 95%CI:13.9-20.2%), 1-3 years (15.0%, 95%CI:13.0-17.3%) and 4-6 years (10.5%, 95%CI:8.6-12.7%) and very low in former smokers of >6 years (0.7%, 95%CI:0.5-0.9%). Similar patterns were observed for daily e-cigarette use. Current e-cigarette use was negatively associated with being a former smoker when quit duration was ignored (aPR:0.64, 95%CI:0.59-0.69) but was positively associated with being a former smoker of <1 year (aPR:1.44, 95%CI:1.12-1.84) and 1-3 years (aPR:1.21, 95%CI:1.03-1.42). Daily e-cigarette use was not associated with being a former smoker when quit duration was ignored but was positively associated with being a former smoker of <1 year (aPR:3.44, 95%CI:2.63-4.49), 1-3 years (aPR:2.51, 95%CI:2.13-2.95) and 4-6 years (aPR:1.84, 95%CI:1.49-2.26).

CONCLUSIONS: Daily e-cigarette use is strongly associated with recent smoking cessation (< 6 years) among US adults. Frequency of e-cigarette use and smoking cessation duration are important parameters when analyzing the effects of e-cigarettes in population surveys.