title: Sexual and testing behaviour associated with Chlamydia trachomatis infection: a cohort study in an STI clinic in Sweden.
abstract: Genital chlamydia infection (chlamydia) is the most commonly reported sexually transmitted infection (STI) in Sweden. To guide prevention needs, we aimed to investigate factors associated with chlamydia.
  
  
  
  A cohort of visitors aged 20-40 years at an urban STI clinic in Sweden was recruited. Behavioural data were collected using a self-administered questionnaire. Self-sampled specimens were tested for chlamydia by a DNA amplification assay. Statistically significant (p<0.05) and epidemiologically relevant covariates were entered in a multivariate Poisson model adjusted for potential confounders (age and gender). Backward stepwise elimination produced a final model. Multiple imputation was used to account for missing values.
  
  
  
  Out of 2814 respondents, 1436 were men with a chlamydia positivity rate of 12.6% vs 8.9% in women. Lifetime testing for chlamydia and HIV was high (82% and 60%, respectively). Factors significantly associated with chlamydia were: 20-24 years old (adjusted risk ratio (ARR)=2.10, 95% CI 1.21 to 3.65); testing reason: contact with a chlamydia case (ARR=6.55, 95% CI 4.77 to 8.98) and having symptoms (ARR=2.19, 95% CI 1.48 to 3.24); 6-10 sexual partners (ARR=1.53, 95% CI 1.06 to 2.21); last sexual activity 'vaginal sex and oral sex and anal sex and petting' (ARR=1.84, 95% CI 1.09 to 3.10); alcohol use before sex (ARR=1.98, 95% CI 1.10 to 3.57); men with symptoms (ARR=2.09, 95% CI 1.38 to 3.18); tested for chlamydia (ARR=0.72, 95% CI 0.55 to 0.94).
  
  
  
  Risk factors associated with chlamydia were consistent with previous reports in similar settings and suggest no major changes over time. Increased risk for chlamydia infection associated with high-risk behaviour (eg, alcohol use, increased number of sexual partners) supports the need for behavioural interventions in this population such as promotion of safer sex behaviour (condom use) and testing.
authors: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden Unit of Monitoring and Evaluation, Public Health Agency of Sweden, Stockholm, Sweden.
authors: Inga
authors: I
authors: Veličko
authors: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors: Alexander
authors: A
authors: Ploner
authors: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors: Pär
authors: P
authors: Sparén
authors: Department of Clinical Science and Education, Karolinska Institutet, Stockholm, Sweden Section of Obstetrics and Gynaecology, Stockholm South General Hospital, Stockholm, Sweden.
authors: Lena
authors: L
authors: Marions
authors: Section of Clinical Microbiology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
authors: Björn
authors: B
authors: Herrmann
authors: Unit of Monitoring and Evaluation, Public Health Agency of Sweden, Stockholm, Sweden.
authors: Sharon
authors: S
authors: Kühlmann-Berenzon
mesh_terms: D000328:Adult; D002690:Chlamydia Infections / Q000453:epidemiology* / Q000517:prevention & control; D002692:Chlamydia trachomatis; D003267:Contraception / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D016017:Odds Ratio; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D012309:Risk-Taking; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D012747:Sexual Partners; D013548:Sweden; D055815:Young Adult
keywords: EPIDEMIOLOGY; PUBLIC HEALTH