Young adults often have misconceptions about whether a new sexual partner has other partners, and those with such misconceptions may be at increased risk of being infected with a sexually transmitted disease (STD).1 In a clinic-based sample of 18–30-year-olds in California, 74% of men and women whose partner had had another partner at some time during their relationship were not aware of this; the odds of being infected with trichomonas or chlamydia were 4.5 times as high in this group as among individuals who correctly believed that their partner had been monogamous. The odds of infection were similarly elevated among the 14% of men and women who incorrectly believed that their partner had had sex outside their relationship.
The sample consisted of 96 heterosexual couples attending STD and family planning clinics in San Diego in 2000–2001, who had begun a sexual relationship within the previous three months. In a one-hour computer-assisted interview, participants provided information about their demographic characteristics, sexual behavior (including whether they had had other partners since the beginning of the current relationship) and perception of whether their partner had had other partners during their relationship; members of each couple were interviewed simultaneously but separately. All participants were tested for chlamydia, gonorrhea and trichomonas infection.
Nearly half of the sample were white; the median age was 22, and the median number of years of education was 13. On average, both men and women had begun having intercourse at age 16, had had 4.3 partners during the previous year and had had 1.4 partners during the previous month. Men had had a lifetime average of 20.2 partners, and women had had 13.9; the difference, when adjusted for age, was not statistically significant. One-quarter of participants reported consistent condom use in the month before the interview, and three in 10 reported no use. None were infected with gonorrhea, but 12% tested positive for chlamydia or trichomonas.
Thirty-two percent of participants said that they had had another partner since beginning the current relationship; 16% believed that their partner had done so. Thirty-one percent were wrong about their partner: Seventy-four percent of those whose partner reported sexual activity outside their relationship believed that their partner had been monogamous, and 14% of those whose partner reported no concurrent partnerships thought that he or she had had sex outside their relationship.
Results of univariate analyses using chi-square and t-tests suggested that the likelihood of STD infection was not elevated among men and women who had had concurrent partners, but it was increased among the partners of such individuals. Furthermore, the odds appeared to be elevated for participants who were unaware that their partner had been nonmonogamous and for those who said that the sexual relationship had begun within one week after the couple met. Other sexual risk factors, recent condom use and demographic characteristics (except residence in south San Diego) were not related to the likelihood of having an STD.
Each of three multivariate logistic regression models included a different measure of concurrent partnerships: whether the respondent had had sex outside the relationship, whether the respondent thought his or her partner had done so and the accuracy of the respondent's perception of his or her partner's behavior. The first model confirmed that individuals who had been nonmonogamous did not have an increased likelihood of being infected with chlamydia or trichomonas. The second showed that men and women whose partner had had another partner had significantly elevated odds of infection (odds ratio, 3.6). The third indicated that for those who incorrectly thought either that their partner had been monogamous or that their partner had had a concurrent partner, the likelihood of infection was increased (4.5 and 4.7, respectively). In all three models, those who reported having begun the sexual relationship within a week after meeting their partner were at increased risk (6.6–9.1), as were residents of south San Diego (3.8–5.1); commitment to continuing the relationship was associated with an increased likelihood of infection in the second and third models.
The researchers conclude that although their study could be limited by reporting biases and the small sample, it demonstrates that young people's "poor ability to assess a partner's behavior is associated with increased risk" of STD infection. They note the need for larger studies, which should involve couples and be designed to permit detailed examination of condom use by motivations for concurrent partnerships or by which partner has had sex outside the relationship.
1. Drumright LN, Gorbach PM and Holmes KK, Do people really know their sex partners? concurrency, knowledge of partner behavior, and sexually transmitted infections within partnerships, Sexually Transmitted Diseases, 2004, 31(7):437–442.