title: Sexually Transmitted Infections and First Sexual Intercourse Age in Adolescents: The Nationwide Retrospective Cross-Sectional Study.
abstract: BACKGROUND
  Sexually transmitted infections (STIs) are major causes of medical and psychological problems globally, while adolescents in South Korea have recently shown rapid changes in sexual behaviors.
  
  
  OBJECTIVE
  We aimed to examine the association between the age of first sexual intercourse and the experience of STIs among adolescents. Additionally, in which specific time period would more likely to get infected from sexual intercourse.
  
  
  METHODS
  We used data from the 2007-2013 Korea Youth Risk Behavior Web-based Survey. Only adolescents with sexual intercourse experience (N = 22,381) were included, and multiple logistic regression analysis was performed.
  
  
  METHODS
  One dichotomized measure and one continuous measure were assessed: (i) STIs experience (defined as having had STIs); and (ii) association between STIs experience and absolute age gap (defined as temporal differences between secondary sexual character emergence age and first sexual intercourse age).
  
  
  RESULTS
  Approximately 7.4% of boys and 7.5% of girls reported had STI. For both boys and girls, the chance of experiencing STIs increased as the age of first sexual intercourse decreased (boys: before elementary school [age 7 or under]: odds ratio [OR] = 10.81, first grade [age 7 or 8]: OR = 4.44, second grade [age 8 or 9]: OR = 8.90, fourth grade [age 10 or 11]: OR = 7.20, ninth grade [age 15 or 16]: OR = 2.31; girls: before elementary school: OR = 18.09, first grade: OR = 7.26, second grade: OR = 7.12, fourth grade: OR = 8.93, ninth grade: OR = 2.74). The association between the absolute age gap and STI experience was examined additionally (boys: OR = 0.93, girls: OR = 0.87).
  
  
  CONCLUSIONS
  This study shows that earlier initiation of sexual intercourse increases the odds of experiencing STIs. Also as the age gap gets shorter, the odds of experiencing STIs increase. Our study suggests that it is important to consider the time period of first sexual intercourse and to reinforce a monitoring system along with the development of other preventive strategies.
authors.affiliation: Department of Health Policy and Management, Graduate School of Public Health, Yonsei University, Seoul, South Korea.|Institute of Health Services Research, Yonsei University, Seoul, South Korea.
authors.forename: Seo Yoon
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, South Korea.|Department of Public Health, Graduate School, Yonsei University, Seoul, South Korea.
authors.forename: Hyo Jung
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, South Korea.|Department of Public Health, Graduate School, Yonsei University, Seoul, South Korea.
authors.forename: Tae Kyoung
authors.initials: TK
authors.lastname: Kim
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, South Korea.|Department of Hospital Management, Graduate School of Public Health, Yonsei University, Seoul, South Korea.
authors.forename: Sang Gyu
authors.initials: SG
authors.lastname: Lee
authors.affiliation: Institute of Health Services Research, Yonsei University, Seoul, South Korea.|Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, South Korea.
authors.forename: Eun-Cheol
authors.initials: EC
authors.lastname: Park
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000067697:Adolescent Health; D000367:Age Factors; D003075:Coitus / Q000523:psychology*; D003430:Cross-Sectional Studies; D005260:Female; D006266:Health Education; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008297:Male; D016017:Odds Ratio; D000067074:Peer Influence; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D012309:Risk-Taking; D012725:Sexual Behavior / Q000523:psychology*; D012749:Sexually Transmitted Diseases / Q000517:prevention & control / Q000523:psychology*; D055815:Young Adult
keywords: Adolescent; Sexual Health; Sexually Transmitted Infection; Timing