Background: The aim of this study was to assess the prevalence of women reporting ever having genital chlamydia, genital herpes, Trichomonas vaginalis, and gonorrhea, and to identify factors associated with each of these sexually transmitted infections (STIs).
Methods: The study was based on a large cross-sectional survey conducted in 2004-2005 among randomly sampled women (18-45 years) from the computerized population registries in Denmark, Iceland, Norway, and Sweden. A total of 69,567 women were included in the study.
Results: The overall prevalence in Denmark, Iceland, Norway, and Sweden was 1.5% for reporting ever having had Trichomonas vaginalis, 1.9% for gonorrhea, 4.8% for genital herpes, and 17.0% for genital chlamydia. The prevalence of each of these STIs varied with birth cohort and country. In addition, they were strongly associated with lifetime number of partners and having a previous diagnosis of another sexually transmitted infection. Moreover, a diagnosis of genital chlamydia or gonorrhea was associated with early age at first intercourse and smoking initiation. Finally, reporting genital chlamydia was associated with early age at drinking initiation, and ever use of hormonal contraceptives and condoms.
Conclusion: Genital chlamydia occurs frequently among women in the Nordic countries. Risk-taking behavior, particularly sexual behavior, is strongly associated with STIs, which suggest that further information is needed about STIs and their consequences, targeting high-risk groups. There is also a need for continued monitoring of STIs in order to follow the prevalence and to gain further knowledge about risk factors.