title: E-cigarettes, conventional cigarettes, and dual use in Korean adolescents and university students: Prevalence and risk factors.
abstract: To examine risk factors associated with use of e-cigarettes only, conventional cigarettes only, and dual use in Korean adolescents and young adults.
  
  
  
  In a cross-sectional study, anonymous questionnaires were completed between April-May, 2015 among 1) 2744 middle and high school students, aged 13-18, from Seoul, Incheon, Gyeonggi, and Cheongju, Korea and 2) 2167 university students, aged 19-29, from fourteen universities in Korea.
  
  
  
  The results show that 12.6% of adolescents and 21.2% of university students reported having ever tried e-cigarettes at least once. Among the ever e-cigarette users, 95.1% and 96.3% of adolescents and university students also tried conventional cigarettes, respectively. Dual users were more likely to be male (adolescents: OR 2.63, 95% CI 1.93-3.57; university students: 4.28, 3.21-5.70), have any close friends who smoke (adolescents: 11.56, 7.63-17.53; university students: 11.29, 5.52-23.10), have any siblings who smoke (adolescents: 3.17, 2.25-4.46; university students: 1.78, 1.30-2.43), and have observed teachers smoke cigarettes at school (adolescents: 1.45, 1.05-2.01).
  
  
  
  A majority of e-cigarette users were dual users. Friends' and siblings' smoking status were significantly associated with dual product use in adolescent and young adult populations. Surveillance of e-cigarette use and implementation of evidence-based behavioral interventions targeting adolescents and young adults are necessary.
authors.affiliation: Department of Epidemiology and Health Promotion, Institute for Health Promotion, Graduate School of Public Health, Yonsei University, Seoul 120-752, Republic of Korea; Department of Public Health, Graduate School, Yonsei University Seoul 120-752, Republic of Korea.
authors.forename: Christina
authors.initials: C
authors.lastname: Jeon
authors.affiliation: Department of Epidemiology and Health Promotion, Institute for Health Promotion, Graduate School of Public Health, Yonsei University, Seoul 120-752, Republic of Korea; Department of Public Health, Graduate School, Yonsei University Seoul 120-752, Republic of Korea.
authors.forename: Keum Ji
authors.initials: KJ
authors.lastname: Jung
authors.affiliation: Department of Epidemiology and Health Promotion, Institute for Health Promotion, Graduate School of Public Health, Yonsei University, Seoul 120-752, Republic of Korea.
authors.forename: Heejin
authors.initials: H
authors.lastname: Kimm
authors.affiliation: National Evidence-based Healthcare Collaborating Agency, Seoul, Republic of Korea.
authors.forename: Sungkyu
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Preventive Medicine, University of Southern California, Los Angeles, CA, United States.
authors.forename: Jessica L
authors.initials: JL
authors.lastname: Barrington-Trimis
authors.affiliation: Department of Preventive Medicine, University of Southern California, Los Angeles, CA, United States.
authors.forename: Rob
authors.initials: R
authors.lastname: McConnell
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, Institute for Global Health, University of Southern California, Los Angeles, CA, United States.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Samet
authors.affiliation: Department of Epidemiology and Health Promotion, Institute for Health Promotion, Graduate School of Public Health, Yonsei University, Seoul 120-752, Republic of Korea; Department of Public Health, Graduate School, Yonsei University Seoul 120-752, Republic of Korea. Electronic address: jsunha@yuhs.ac.
authors.forename: Sun Ha
authors.initials: SH
authors.lastname: Jee
mesh_terms: D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D066300:Electronic Nicotine Delivery Systems / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D015995:Prevalence; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology*; D013334:Students; D011795:Surveys and Questionnaires; D062789:Tobacco Products / Q000706:statistics & numerical data*; D014495:Universities; D055815:Young Adult
keywords: Adolescents; Dual use; Electronic cigarettes; University students