Cigarette smoking and E-cigarette use among young adults in the United States: Findings from the 2016-18 behavioral risk factor surveillance system.

Because there are few proven smoking cessation approaches for young adults, it is critical to consider the potential of e-cigarettes as an option. Evidence from 2012 to 2013 in the United States (U.S.) suggested that current e-cigarette use was associated with a higher probability of daily smoking and a lower probability of quitting among young adults. This study examines the associations between e-cigarette use frequency and cigarette smoking in more recent data. Data on e-cigarette use were available for 32,656 current smokers and 9,565 past-year quitters ages 18-34 in the 2016-2018 U.S. Behavioral Risk Factor Surveillance System. Participants were categorized as "daily", "non-daily", "former", or "never" e-cigarette users. Adjusted prevalence ratios were estimated to test the associations between e-cigarette use and each of daily smoking and past-year cessation. With e-cigarette never-users as the reference: 1) daily e-cigarette users were 30% (95%CI 0.61-0.79) less likely to be daily smokers; non-daily and former e-cigarette users were 8% (95%CI 1.02-1.15) and 16% (95%CI 1.11-1.21) more likely to be daily smokers, respectively; 2) daily e-cigarette users were 54% (95%CI 1.38-1.73) more likely to have quit in the past year; non-daily and former e-cigarette users were 50% (95%CI 0.42-0.59) and 21% (95%CI 0.73-0.86) less likely to have quit in the past year, respectively. The findings suggest that non-daily e-cigarette use was associated with greater frequency of smoking and less quitting whereas daily e-cigarette use was associated with a lower frequency of smoking and more quitting among young adults in 2016-18.