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High Prevalence and Incidence of Sexually Transmitted Diseases in Urban Adolescent Females Despite Moderate Risk Behaviors

Original article by: Bunnell R., Dahlberg L., Rolfs R. et al

Each year, an estimated three million teenagers in the United States acquire a sexually transmitted disease (STD). Of those teens, females are at greatest risk due to physiologic and social factors. Physiologically, the innermost cells of the cervix of an adolescent female are more exposed than those of an adult woman, making the cervix more vulnerable to STD infection. Socially, teens often lack the power and skill to refuse sexual involvement or demand safer sex.

Researchers Bunnell et al recently conducted a study that attempted to: (1) assess the prevalence and incidence of STDs in adolescent females attending teen clinics, (2) describe risk behaviors and partner characteristics in that population, and (3) identify risk behaviors for STDs among teenage females.

Methods

The participants for the study came from four neighborhood teen health clinics in a large Southeastern U.S. city that provided family planning, HIV and STD testing, and general exam services. Participants ages 14-19 who had had sexual intercourse at least once and were visiting the clinic for a service that included a pelvic exam were selected for the study.

Participants were given a face-to-face interview by trained African-American female interviewers who were not part of the clinics' staff. The interview included demographic information, sexual and reproductive history, contraceptive practices, STD knowledge and history, drug and alcohol use, and information on current and past sexual partners.

Each participant was then given a physical exam which included endocervical samples for chlamydia and gonorrhea, serum samples for syphilis, hepatitis B and C and HSV-2, wet mounts and trichomoniasis cultures, and a urine sample for pregnancy. HPV (human papilloma virus) infection was not assessed. Any STD found at the enrollment visit was labeled a "prevalent infection."

Teens found to have a curable STD were treated and urged to inform their partners for screening and treatment. Teens were followed up six months later and given a repeat interview and exam. All STDs diagnosed at follow-up were labeled "incident infections."

Results

Of the 691 teens who were eligible, 650 participated in the study. Of those, only 501 returned for their follow-up visits, and 484 had complete STD specimens and results available. Participants' median age was 16 years old; 93% were African-American, 53% were supported only by their biologic mother, and 93% were enrolled in school. Teens who returned for follow-up had similar characteristics to those who didn't return.

At enrollment, 39% of the participants visited the clinic for an annual exam, 29% to start birth control, 12% for an infection check, and 9% for a pregnancy test. The remaining 11% visited for a variety of other reasons, such as a sports physical. It is notable that 87% of the young women diagnosed with a prevalent infection at enrollment came to the clinic for reasons other than a suspected infection.

Of the 484 teens who completed specimens at both visits, 257 (53%) had more than one STD either at enrollment or follow-up. More than 38% were infected with chlamydia, 17% with HSV-2, 9% with gonorrhea, and 6% with trichomoniasis.

Few demographic and behavioral factors were significantly associated with acquiring an STD. Engaging in sexual intercourse prior to 15 years of age, acquiring a new sex partner in the month prior to the follow-up visit, having an STD at the time of enrollment and having more than one partner during the six months between enrollment and follow-up were all factors that contributed to the likelihood of contracting an STD. Teens with more than five lifetime partners were more than twice as likely to have an STD than those with only one lifetime partner. The education level and employment status of the participant's primary provider were only marginally significant.

In a multivariate analysis, only a few factors remained significantly associated with having an STD. Having a new sex partner in the month prior to the follow-up visit more than doubled the likelihood of having an STD compared with those who didn't have a new partner. Having friends who sold cocaine was associated with higher risk, while believing that condoms were effective against STDs was associated with lower risk (although the significance for both factors was marginal).

Discussion

The authors note that the STD burden among their sample population was extremely high. While there was a high prevalence and incidence of STDs among teens who had more than one partner, the same was true for those with only one lifetime partner. Since over 50% of this population had more than one STD in a six-month period, and STDs increase the risk of HIV transmission, this group is at high risk for HIV infection.

The authors also note that socioeconomic status was only weakly correlated with STD infection and caution against stereotyping this group as an inner-city population with limited resources. They argue that the high incidence of STD infection despite only moderate risk behaviors suggests the need for policy- and community-level interventions in addition to the more common interventions focused on individual behavior changes.

The authors recommend:

  • widespread, frequent screenings for all sexually active teens as the majority who had an STD were asymptomatic,

  • school-based interventions as the vast majority of the study participants were attending school full-time,

  • routine hepatitis B vaccination,

  • contraceptive promotion and education on adverse pregnancy outcomes associated with STDs,

  • improved methods for promoting protective behaviors that are both culturally and behaviorally relevant, recognizing that many of today's teens may be sexually active,

  • improved education on asymptomatic HSV-2 transmission,

  • theoretical and practical skills-building training that is creative and culturally relevant,

  • more intervention targeted towards men which is indicated by the high rate of chlamydia re-infection seen in the study, suggesting that partner follow-up strategies are insufficient,

  • interventions that include targeting teens connected to social and sexual networks of drug users and who do not identify themselves as users as there was a high prevalence of STDs within populations where drug selling is common.

Furthermore, the authors indicate that -- since many of the participants in this study were asymptomatic at enrollment -- the rates of STD infection found in their study may be higher than studies based on findings from STD clinics. Yet they also suggest that because the young women in this study had access to health care clinics and STD rates are typically higher in areas where access is limited, their findings may underrepresent actual infection rates.

The study had some notable limitations. First, there was a weak association between condom use and STD incidence, possibly due to the following:

  • Answers given by teens about condom use may have been influenced by their perceptions of social desirability or the face-to-face nature of the questionnaire.

  • Researchers did not know if teens were correctly using condoms or engaging in oral sex, body rubbing, or other sexual activities.

  • Those who reported condom use may have selected partners with an increased risk for STD infection.

These findings suggest that in order to utilize self-reported condom use as a measure of risk or to evaluate the success of prevention programs for this population, researchers need to know how, when, and with whom condoms are used.

Other limitations to consider include:

  • a lack of sufficient power to detect all associations between incident infection and risk and protective factors,

  • the use of a composite variable for all incident STDs, which may have hid disease-specific risk factors,

  • changes over time in sexual behaviors and other factors affecting incidence as the data were collected from 1991 to 1993,

  • possible inaccurate information on male partners as it was obtained by participant reports,

  • possible underreporting of total infections as analysis was done only on teens who had complete specimens at both baseline and follow-up,

  • the absence of HPV assessment in the study as it has been suggested by other studies that HPV may be the most prevalent STD in the US.

In closing, the authors note that the burden of STDs in this population is high despite condom use rates and partner characteristics similar to those in a national representative survey. They speculate that monogamy practiced by females alone is insufficient for STD prevention. It is probable that male partners in this population have high rates of STDs and possible that they have numerous adolescent female partners.

Finally, they suggest that "for these sexually active teens, the social environment in which they are having sex may be a more important determinant of their risk of STDs than their own behaviors and that engaging in moderate risk behaviors may have very different consequences in different settings."

Bunnell R., Dahlberg L., Rolfs R. et al, (1999). "High Prevalence and Incidence of Sexually Transmitted Diseases in Urban Adolescent Females Despite Moderate Risk Behaviors." The Journal of Infectious Diseases, 1999; 180: 1624-1631. 

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