Advanced Search Abstract The authors examined the relation between age at first vaginal intercourse and a positive nucleic acid amplification test for sexually transmitted infection STI. A nationally representative sample of 9, respondents aged 18—26 years was tested for chlamydial infection, gonorrhea, and trichomoniasis in wave 3 — of the National Longitudinal Study of Adolescent Health. The authors used multiple logistic regression to assess the relation between age at first sexual intercourse and these STIs and to examine variation by current age, sex, race, and ethnicity.
Younger ages at first intercourse were associated with higher odds of STI in comparison with older ages, but the effect diminished with increasing current age. Thus, earlier initiation of sexual intercourse is strongly associated with STIs for older adolescents but not for young adults over age 23 years. Early initiation of sexual intercourse has been linked to increased risk of sexually transmitted infections STIs and pregnancy during adolescence 2 , 3.
The increased STI risk is due, in part, to a biologic predisposition of the immature cervix to infection if exposed 4 — 6 and to the increased likelihood of engaging in riskier sexual behaviors among persons who initiate sexual intercourse at younger ages 3 , 7 — 9. Over the past several years, substantial funding has been directed toward programs designed to delay first sexual intercourse among adolescents i.
Little is known about the long-term consequences of early sexual intercourse. Life-course theory proposes that societal expectations exist regarding the appropriate times for important transitions, and there can be consequences if life events do not meet these normative expectations 10 — With regard to sexual behavior, adolescents develop elaborate sets of ideas concerning sexuality and their sexual roles well before they actually engage in sexual activity Nonnormative sexual scripts and early first sexual intercourse an off-time event may represent a life-course transition that increases the likelihood of a longitudinal pattern of risky sexual activity.
Negative consequences may accumulate to affect sexual functioning and relationship skills 16 , The subsequent sexual trajectory may produce adverse adult outcomes, such as elevated risk of STI. Whether delaying first sexual intercourse among adolescents influences risk of STI in young adulthood is unknown.
This is an important question, because contracting STIs during young adulthood can have significant adverse consequences for reproductive health. STIs can cause complications such as pelvic inflammatory disease, infertility, ectopic pregnancy, preterm birth, and fetal abnormalities 18 , STIs may also increase the risk of transmission of human immunodeficiency virus 19 , Young adults aged 18—24 years report much higher annual rates of STI than older adults and carry a heavy disease burden 15 , If delaying sexual intercourse in adolescence carries a lasting benefit of reduced STIs in young adulthood, this would represent a potentially huge impact for such a strategy in terms of long-term health benefits in the population.
Alternatively, if the benefits of delaying intercourse do not last into adulthood, different strategies addressing the health education and service needs of young adults should be emphasized.
Most studies that have investigated the link between age at first sexual intercourse and risk of STI among young adults have focused only on females and have used convenience samples, self-reports of STI, or both. Results have been mixed. In Europe, women aged 16—44 years visiting family planning centers who reported first having intercourse at age 16 or younger did not have a greater prevalence of Chlamydia trachomatis In contrast, women visiting Planned Parenthood clinics in Pennsylvania who reported first having sex before age 15 were more likely to self-report having an STI in the past 5 years In the National Survey of Family Growth, women who reported earlier first intercourse were also more likely to report a history of bacterial STI Little is known about the relation between age at first sexual intercourse and longitudinal risk of STI by sex, race, or ethnicity.
These demographic factors have been associated with variation in mean age of first sexual intercourse and with extremely wide variation in STI prevalence 21 , 24 — Early sexual intercourse may be more normative in some socioeconomic, racial, ethnic, or sex groups and thus may not be tied to nonnormative risk behaviors or to longitudinal risk of STI 27 — Therefore, the long-term impact of programs aimed at prolonging virginity may vary among groups of young adults and may mitigate or exacerbate current disparities.
In this study, our goal was to clarify the long-term sexual health consequences of the timing of first sexual intercourse and to elucidate how such consequences might vary by characteristics of the individual. We examined the following research questions: Add Health was designed to examine the determinants of health and health-related behaviors of adolescents who were enrolled in the study in grades 7—12 during the — school year.
For construction of the original wave 1 sample, which was representative of all US schools with respect to region, urbanicity, school size, school type, and ethnicity, 80 high schools and 52 middle schools were selected using systematic sampling methods and implicit stratification.
Wave 1 included an in-home questionnaire that was administered to over 20, adolescent students from the sample schools. In wave 3, conducted from August through April , 15, of the original wave 1 respondents were reinterviewed. Add Health respondents ranged in age from 18 years to 26 years at wave 3.
Of the 14, respondents with assigned sampling weights in wave 3, 12, reported ever having had intercourse. Of those, 9, had complete data on our variables of interest, with almost all of the missing data being attributable to respondents' lacking results for the biologic STI laboratory tests approximately 8 percent of respondents chose not to provide a specimen; approximately 2 percent were unable to provide a specimen at the time of the interview; 3 percent of specimens could not be processed because of shipping and laboratory problems; and 6 percent of the N.
The 9, persons with complete data made up our study sample. Measures Respondents were asked at wave 3 to provide a urine specimen for STI testing. These specimens were analyzed for the presence of C. A ligase chain reaction assay was used to detect the presence of C.
We chose this composite measure because of the low prevalence of N. Furthermore, although the sexual network structures may have differed somewhat between these infections, the sexual behavioral risks were likely to have been similar. This composite measure provided us with a more comprehensive measure of each respondent's sexual health status.
Analyses using chlamydial infection alone as the outcome not shown produced results similar to those for all three STIs combined. During the in-home interviews, a questionnaire containing sensitive questions on sexual activity was administered using computer-assisted self-interviewing technology.
Age at first sexual intercourse was used as a continuous variable. Current age was defined as the respondent's age at the time of wave 3 questionnaire administration and was also used as a continuous variable. Other variables included the sex of the respondent male referent vs. Latino , race White referent vs. Black or other , and parental education highest level of education attained by either parent, categorized as less than high school referent , completion of high school, some additional training, and college graduation.
Data analysis We used Stata software version 7. All estimates were standardized to US Census data on the demographic characteristics of the adolescent population, as recommended by the Add Health research team In preliminary analyses, we examined the frequency distributions of the variables of interest for the entire sample and for persons testing positive for STIs.
We used simple logistic regression to obtain adjusted estimates of the prevalence odds ratios for having an STI at wave 3. Respondent's sex, race, ethnicity, and parental education, which are associated with contracting an STI, were controlled for in multiple logistic regression analyses. Inclusion of both current age and age at first sexual intercourse in these models controlled for the length of time a participant had been sexually active.
Therefore, our measure of age at first sexual intercourse does not represent the effects of exposure time. In addition to controlling for potential confounding in our models, we also examined whether the relations between early sexual intercourse and STIs were the same for different groups of respondents. We included interaction terms in the full logistic regression model to determine whether the association between age at first intercourse and STI prevalence varied by the sex, race, ethnicity, parental education, or current age of the respondent.
In the initial full model, all variables and terms for interaction with age at first sexual intercourse were entered simultaneously. The majority of respondents were White and non-Latino table 1. The mean current age in our study sample at wave 3 was Age at first sexual intercourse ranged from 10 years through 25 years, with a mean of Approximately one third of participants had had intercourse by age 15 years, and over 90 percent had had intercourse by age 19 years.
Age at first sexual intercourse was not associated with being dropped from the sample due to incomplete data. A total of participants almost 7 percent of the weighted sample tested positive for at least one STI at wave 3. When examined in 1-year age increments, the STI prevalence for all current ages was above 5 percent.