title: Risk Factors for Incident and Redetected Chlamydia trachomatis Infection in Women: Results of a Population-Based Cohort Study.
abstract: OBJECTIVE
  To investigate risk factors for incident and redetected Chlamydia trachomatis (CT) infection in women, including the role of high-risk human papillomavirus (HPV).
  
  
  METHODS
  In this population-based, prospective cohort study conducted in Copenhagen, Denmark, 10,729 women aged 20 to 29 years were tested for CT and HPV DNA and provided information on sexual and health behavior at baseline. Of these, 7998 (74.5%) participated in a follow-up visit 2 years later with identical data collection. We used logistic regression to investigate risk factors for incident and redetected CT infection at follow-up.
  
  
  RESULTS
  Among CT DNA negative women at baseline (n = 7529), 106 (1.4%) were CT DNA positive at follow-up (incident infection). Increasing number of sexual partners during follow-up (odds ratio [OR], 1.07 per partner; 95% confidence interval (CI), 1.02-1.11), low educational level (OR, 1.69; 95% CI, 1.11-2.56; for basic education vs. high school or higher), and high-risk HPV positivity at baseline (OR, 1.66; 95% CI, 1.06-2.58) were risk factors for incident infection, whereas older age (OR, 0.86 per year increase; 95% CI, 0.80-0.93) and condom use (OR, 0.60; 95% CI, 0.38-0.94) were associated with reduced risk. Among CT DNA positive women at baseline (n = 469), 108 (23.0%) tested positive at follow-up (redetected infection). We found no statistically significant associations between age, educational level, sexual behavior, smoking, or high-risk HPV status and the risk for redetected CT.
  
  
  CONCLUSIONS
  Young age, low educational level, high number of sexual partners, failure to use condoms, and high-risk HPV positivity are associated with increased risk for incident CT infection. These findings may guide the development of targeted CT prevention strategies, including screening and information campaigns.
authors.affiliation: From the Departments of *Virus, Lifestyle and Genes, and †Statistics, Bioinformatics and Registry, Danish Cancer Society Research Center, Copenhagen, Denmark; ‡Division Experimental Virology, University Hospital of Tübingen, Tübingen, Germany; §Laboratory for Molecular Diagnostics, Departments of Medical Microbiology and Pathology, Jeroen Bosch Hospital, 's-Hertogenbosch, the Netherlands; and ¶Department of Gynecology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Elise
authors.initials: E
authors.lastname: Harder
authors.forename: Louise T
authors.initials: LT
authors.lastname: Thomsen
authors.forename: Kirsten
authors.initials: K
authors.lastname: Frederiksen
authors.forename: Christian
authors.initials: C
authors.lastname: Munk
authors.forename: Thomas
authors.initials: T
authors.lastname: Iftner
authors.forename: Adriaan
authors.initials: A
authors.lastname: van den Brule
authors.forename: Susanne K
authors.initials: SK
authors.lastname: Kjaer
mesh_terms: D000328:Adult; D002690:Chlamydia Infections / Q000175:diagnosis / Q000453:epidemiology*; D002692:Chlamydia trachomatis / Q000235:genetics / Q000302:isolation & purification*; D015331:Cohort Studies; D017280:Condoms / Q000706:statistics & numerical data; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016015:Logistic Models; D027383:Papillomaviridae / Q000235:genetics / Q000302:isolation & purification*; D030361:Papillomavirus Infections / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors; D012725:Sexual Behavior; D012747:Sexual Partners; D055815:Young Adult