During adolescence, youth explore their sexuality by pursuing romantic interests, exploring their sexual identity, and engaging in sexual relationships. As adolescents transition into young adulthood, the exploration of sexuality becomes less restricted prior to settling into stable relationships such as marriage (Arnett, 2000), yet their healthy sexual development may be limited by risks and vulnerabilities present in their social contexts (Aggleton, 2004; Alan Guttmacher Institute [AGI], 2005). Youth from disadvantaged backgrounds (i.e., racial and ethnic minorities and/or from a lower socioeconomic position) are more likely to be exposed to social, physical, and economic risks that may limit their safer sex decision making and increase vulnerability to HIV, AIDS, sexually transmitted infections (STIs), and unintended pregnancies. In the United States, African Americans have approximately ten times greater risk for HIV infection than their White counterparts (Centers for Disease Control [CDC], 2007). These racial differences are even greater when stratified by sex. African American men are eight times more likely to contract HIV than their White male counterparts. Among women, African Americans are 25 times more likely to be infected than their White counterparts. HIV infection is also patterned by socioeconomic status, with adolescents' and young adults' HIV and STI incidence decreasing as parents' socioeconomic status increases and youth complete their high school education (Ford & Lepkowski, 2004). These disparities highlight the importance of developing effective HIV and STI prevention and sex education messages that are informed by empirical research exploring how sexual risk-taking behavior occurs among youth and their sexual partners.
Sex Partners' Age and Sexual Risk-Taking Behaviors
As youth pursue and engage in sexual relationships during adolescence and young adulthood, they may develop sexual relationships with younger or older partners. While researchers and policymakers have suggested that age differences between youth and their sex partners may serve as a marker of sexual power imbalances, the association between partners' age and sexual risk-taking behavior has focused on the detrimental relationship between older partners and youth. Researchers have found older sex partners are associated with increased sex risk behaviors including earlier sexual debut (Rich & Kim, 2002), lower condom and contraceptive use (DiClemente et al., 2001), STI history (Ford & Lepkowski, 2004), and intimate partner violence (Gielen, McDonnell, & O'Campo, 2002). Nonetheless, these findings are inconsistent across studies. Kissinger and colleagues (2002), for example, found no evidence to suggest that older partners were associated with recurrence of chlamydia.
The variability across study findings may be attributable to sample characteristics, including the age and gender of participants, the measurement and operationalization of partner age, and the study design. Concerning age, for example, Kaestle, Morisky, and Wiley (2002) found that the magnitude of the association between partner's age and sex risk decreased as youth grow older. In addition, most studies have focused solely on females; as a result, we do not know how partner age differences vary across sex, as well as by other demographic characteristics (i.e., socioeconomic status and education) associated with HIV and STI risk. As we know relatively little regarding what predicts sex partners' age differences across adolescence and young adulthood, we explored whether sex partners' age differences vary by youth's sex, mother's educational attainment, or high school dropout.
Most researchers studying sex partners' age have operationalized sex partner age as a categorical variable (i.e., partner is two or more years younger, partner is of same age or less than two years apart, partner is two or more years older). Limiting sex partners' age to these arbitrary categorical values, however, masks the relationship between sex partners' age and sex risk behaviors and limits our ability to identify a threshold where age differences between youth and their partners may become deleterious. In an attempt to rectify this measurement concern, Kaestle and colleagues (2002) proposed an age gap measure that accounted for the difference in age between female respondents and their romantic sex partners (e.g., positive values in their measure indicated having an older sex partner). Their results suggest that female participants with older partners were more likely to report sexual intercourse than participants with younger or same-aged partners. Unfortunately, the age gap measure used in their analyses was truncated in the left tail of the distribution, as they chose to group participants with partners of similar age (i.e., age gap is close to zero) and participants with partners of a younger age (i.e., age gap is a negative value). While this operationalization of age differences is noteworthy, it assumes that youth with partners of a similar or younger age are homogeneous and limits our ability to assess any potential risks or benefits that may result when youth have a younger partner. Consequently, we follow Kaestle et al.'s approach to study sex partners' age differences as a continuous variable without truncating the distribution so that positive values represent older sex partners and negative values reflect younger sex partners.
Most studies reporting data on sex partner age differences employ cross-sectional designs (Ford & Lepkowski, 2004), limiting our understanding of the cumulative, long-term effects of age differences on youth's sexual development across adolescence and young adulthood. Recently, Bauermeister, Zimmerman, Gee, Caldwell, and Xue (2009) studied the effects of sex partners' age on various sex risk behaviors (i.e., condom use frequency, sexual intercourse frequency, and number of partners) in a prospective sample of African American male and female youth followed from mid-adolescence to young adulthood. In their study, they found that having older sex partners was associated with decreased condom use frequency, increased sexual intercourse frequency, and greater number of sex partners across adolescence and young adulthood. They did not account, however, for competing arguments that could explain their findings. Youth may increase their HIV and STI risks as they explore their sexuality, yet these increases parallel other developmental changes such as decreases in self-esteem (Galambos, Barker, & Krahn, 2006), increases in alcohol use frequency (Stewart & Power, 2003), and greater exposure to adults as they begin to participate in the labor force (Bauermeister, Zimmerman, Barnett, & Caldwell, 2007). In this study, we modeled sex partners' age differences from middle adolescence to young adulthood and test whether the age difference is associated with predictors of sexual risk-taking behavior (i.e., alcohol use, self-acceptance, and labor force participation) in a prospective sample of African American youth living in an urban city in the Midwest.
Self-Esteem and Sex Risk
Rosenberg (1965) defined self-esteem as the extent to which an individual values and accepts his or her self-worth. The importance of self-esteem in youth's well-being seems to vary as they transition from adolescence into young adulthood. Decreases in self-esteem during adolescence have been associated with greater risk outcomes. Recent evidence, however, suggests that these dips are temporary with most youth regaining their self-esteem as they settle into their social identities during young adulthood (Galambos et al., 2006). In addition, researchers have found that levels of selfesteem vary by race and gender during adolescence and young adulthood. In a nationally representative sample of eighth graders participating in the National Education Longitudinal Study, African American youth had higher self-esteem than White and Latino or Hispanic counterparts across adolescence (Birndorf, Ryan, Auinger, & Aten, 2005). Females also tend to have lower self-esteem than males over adolescence, yet they are more likely to recover their self-esteem at a faster rate than their male counterparts during the young adulthood years (Galambos et al., 2006).
Current public health efforts seeking to mitigate the risk of HIV and STI transmission have focused on decreasing youth's risk by delaying their sexual debut (Sandfort, Orr, Hirsch, & Santelli, 2008) or increasing their consistent condom use (Kirby, Laris, & Rolleri, 2007). In an urban sample of junior high school youth, males with higher self-esteem during early adolescence reported earlier sexual debut than their counterparts with lower self-esteem, while females with higher self-esteem during early adolescence reported later sexual onset than their counterparts with lower self-esteem (Spencer, Zimet, Aalsma, & Orr, 2002). Similarly, increased self-esteem among African American middle to late adolescent females was associated with more positive attitudes toward safer sex behaviors such as condom use, communication with their sex partners, and their self-efficacy to use condoms (Salazar et al., 2005). These results raise questions about whether self-esteem provides males with confidence to become sexually active, or if sexual activity enhances their self-esteem. For females, however, it is unclear if self-esteem helps them negotiate their sexual encounters more safely, or if safe sexual activity enhances their self-esteem.
Self-acceptance, a subcomponent of self-esteem, is a vital element for well-being (Ellis, 1995) and reflects how an "individual fully and unconditionally accepts himself whether or not he behaves intelligently, correctly, or competently and whether or not other people approve, respect, or love him" (Ellis, 1977, p. 101). Greater self-acceptance allows individuals to acknowledge that they are fallible and to reduce the salience of other people's approval when carrying out a behavior (e.g., pressure into not using a condom). Self-acceptance may be a necessary but insufficient condition to improve overall self-esteem (Honey & Durlak, 1998). Nonetheless, youth self-acceptance has been a common component within adolescent HIV and STI prevention efforts as it is posited to be a protective factor against sex risk behaviors (Fergus & Zimmerman, 2005; Salazar et al., 2005; Schulenberg, Maggs, & Hurrelmann, 1997; Zimmerman, Copeland, Shope, & Dielman, 1997). An untested association is whether self-acceptance is associated with sex partner age. For instance, males with lower self-acceptance may seek younger female partners, whereas females with low self-acceptance may pursue older sex partners across adolescence. As male and female youth solidify their adult identity and recover their self-acceptance during the young adulthood years, however, sex partners' age differences may decrease. In this study, we tested this hypothesis by exploring the prospective association between self-acceptance and sex partners' age differences over time and assess whether …