title: Initiation of Electronic Cigarette Use by Age Among Youth in the U.S.
abstract: BACKGROUND
  The rapid increase in electronic cigarette (e-cigarette) smoking among U.S. youth requires data regarding the age pattern of initiation risk for effective tobacco use prevention.
  
  
  METHODS
  Data from the 2014 National Youth Tobacco Survey (N=20,680, aged 11-19 years, 50.6% male) were analyzed using survival analysis in 2016 to quantify the likelihood of e-cigarette use initiation by age, overall and by gender and racial/ethnic groups.
  
  
  RESULTS
  The estimated mean age of e-cigarette initiation was 17.50 (95% CI=17.47, 17.52) years. The estimated hazards of e-cigarette use initiation were 0 up to age 6 years, increased slowly from age 7 to 11 years, and continued with an accelerated increase up to age 17 years before it slowed down. There were significant gender (male > female) and racial/ethnicity (from high to low: multiracial, white, Hispanic, African, and Asian) differences in the age pattern.
  
  
  CONCLUSIONS
  E-cigarette smoking is initiated as young as age 7 years. Different from conventional cigarette smoking with peak initiation risk at age 14-15 years, the likelihood of initiating e-cigarette smoking continues to increase up to age 18 years. The unique age pattern and significant gender and racial/ethnic differences provide useful data to support further research to strengthen tobacco use prevention in the U.S.
authors.affiliation: Department of Epidemiology, University of Florida, Gainesville, Florida.
authors.forename: Xinguang
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Epidemiology, University of Florida, Gainesville, Florida.
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.affiliation: Department of Epidemiology, University of Florida, Gainesville, Florida. Electronic address: ywang48@phhp.ufl.edu.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000208:ethnology; D000367:Age Factors; D002648:Child; D066300:Electronic Nicotine Delivery Systems / Q000706:statistics & numerical data*; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D009749:Nutrition Surveys / Q000706:statistics & numerical data*; D044469:Racial Groups / Q000706:statistics & numerical data; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology* / Q000639:trends; D064424:Tobacco Use / Q000453:epidemiology / Q000517:prevention & control* / Q000639:trends; D014481:United States / Q000453:epidemiology; D055815:Young Adult