Women in this age group are 43% more likely to get chlamydia than women aged 20-24, according to data from England's National Chlamydia Screening Programme.
The numbers are based on more than 16,400 men and women younger than 25 screened for chlamydia, a bacterial infection that is the most commonly reported sexually transmitted disease in England and the U.S.
Unfortunately chlamydia infection is underreported because it can remain silent in many cases. However complications can arise from the untreated infection. Chlamydia can damage a women's reproductive organs leading to pelvic inflammatory disease, ectopic pregnancy, and infertility. In men, untreated infection has also been linked to infertility.
Screening programs are used to detect silent infections in sexually active people and treat those with an undiagnosed infection and their sexual partners.
Overall, the researchers show that 10% of women and almost 13% of men under 25 tested positive for chlamydia at screening in nonspecialized clinics.
Similar numbers have been reported in Sweden and the U.S., say researcher D. Scott LaMontagne, MPH, FRIPH, CS, of the Communicable Disease Surveillance Centre of England's Health Protection Agency, and colleagues.
The researchers also found that youth was a risk factor for women, but not men. Slightly older men -- aged 20-24 --- were more than twice as likely to test positive as men younger than 20.
Behavior also impacted men and women differently.
Behavioral risks were common among men but were not associated with the risk of infection. Fifty-six percent of the men reported having a new sex partner within the last three months and 60% reported having two or more partners within the past year.
"Women of black Caribbean ethnicity were nearly twice as likely to test positive," LaMontagne and colleagues report.
"Similar to women, black Caribbean or mixed ethnicity males were also more than twice as likely to be infected," the researchers say.
Less Risk With Age
The finding that older women are less likely to get chlamydia is supported in a second British survey.
Elisabeth Adams, also of the Communicable Disease Surveillance Center of England's Health Protection Agency, worked with colleagues to review 357 studies on women and chlamydia.
Nearly 8% of women under age 20 screened by general practitioners had chlamydia infection.
Among women aged 25-29, the number with chlamydia dropped to 2.6%. Only 1.4% of women in their 30s tested positive.
Specialized medical clinics had higher numbers, say Adams and colleagues.
For instance, rates edged above 17% among women under 20 at clinics specializing in genital/urinary medicine.
Still, all clinics saw an age-related drop in chlamydia prevalence.
Both studies appear in the October issue of the journal Sexually Transmitted Infections.