QUEBEC CITY – Chlamydia trachomatis, Neisseria gonorrhoeae, and Trichomonas vaginalis peak at different ages, based on data from 386 young women.
Age-specific incidence rates of these three sexually transmitted infections (STIs) in young women have not been well studied, said Wanzhu Tu, Ph.D., of Indiana University, Indianapolis, and colleagues.
In a longitudinal cohort study, the researchers recruited young women aged 14-17 years from three adolescent medicine clinics. The participants completed questionnaires and face-to-face interviews to determine lifetime and recent sexual activity; cervical and vaginal specimens were collected and tested.
Participants were interviewed and tested for STIs every 3 months. The average length of follow-up was 3.5 years. Any participants with positive tests received treatment, according to the findings presented in a poster session at a congress of the International Society for Sexually Transmitted Diseases Research.
The separate baseline prevalence rates for chlamydia, gonorrhea, and trichomoniasis were 11%, 4%, and 6%, respectively.
The combined peak incidence of any of the three infections was approximately 15% at age 20 years.
When the separate incidence of the three infections was examined as a function of age, chlamydia incidence rose gradually from 7% at age 14 years, peaked at approximately 18 years (11%), and then steadily declined to almost 1% at age 24 years. Gonorrhea rose from 1% at age 14 years, peaked at approximately 19 years (4%), and declined gradually to almost 0% until age 24 years. By contrast, the incidence of trichomoniasis infections started slightly above 1% at age 14 years, peaked at approximately 21 years (6%), and remained steady through age 24 years.
The average age of the participants was 15 years, the average age at the time of sexual debut was 14 years, and the average number of sexual partners at study enrollment was three. A total of 89% of the participants were black.
"The estimated STI incidence rates clearly differ by organism, not only in magnitude but also in peak age," the researchers noted.
"Prevalences of the respective organisms in the partner population are likely contributors to the differential risk of STI acquisition," they added. However, the fact that the differences were seen within the same group of young women with relatively few sexual partners suggests that biologically determined differences in age-related susceptibility may play a large role in STI infections, they said.
The researchers said they had no relevant financial disclosures.
For more information about STIs in teens, check out the latest statistics at the Centers for Disease Control and Prevention website.