Number of Sexual Partners and Relationship Status Are Associated With Unprotected Sex Across Emerging Adulthood

Abstract

Sex with multiple partners, consecutively or concurrently, is a risk factor for contracting sexually transmitted infections (STIs) as multiple partner-partner contacts present increased opportunity for transmission. It is unclear, however, if individuals who tend to have more partners also use protection less reliably than those with sexual histories of fewer partners. Longitudinal data can elucidate whether an individual shows a consistent pattern of sex with multiple partners. We used latent class growth analyses to examine emerging adult survey data (N = 2244) spanning 10 waves of assessment across 6 years. We identified three trajectory classes described with respect to number of partners as (a) Multiple, (b) Single, and (c) Rare. Trajectory group, relationship status, and their interactions were tested as predictors of using protection against STIs and pregnancy at each wave. The Multiple Partners class had the greatest odds ratio of reporting sex without protection against STIs and pregnancy, followed by the Single and Rare classes. Exclusive relationship status was a risk factor for unprotected sex at earlier waves, but a protective factor at most later waves. There was no significant interaction between relationship status and trajectory class in predicting use of protection. The Multiple Partners class reported more permissive values on sex and an elevated proportion of homosexual behavior. This group overlaps with an already identified at-risk population, men who have sex with men. Potential mechanisms explaining the increased risk for sex without protection, including communication, risk assessment, and co-occurring risk behaviors are discussed as targets for intervention.

Keywords: Emerging adults; Multiple sex partners; Sexual risk behavior; Trajectory analysis; Unprotected sex.

Fig. 1

Latent class growth analysis model. Structural equation model used to assess longitudinal classes based on number of sex partners over 3 months. Included are data from waves 1 through 10, with relationship status (exclusive or some nonexclusivity) as a time-varying predictor of the number of sexual partners. Variables used as predictors of trajectory class membership (C) included gender, ethnicity, family income, and highest level parental education, personal values, and homosexual behavior

Fig. 2

Predicted number of partners by sexual trajectory. Presented are the predicted number of partners in a 3-month period as determined by sexual trajectory class membership and the time-varying predictor of relationship status. Results showed three classes: a Rare partner class (blue square), a Single partner class (green circle), and a Multiple partner class (orange triangle). The effect of relationship status is indicated by the solid (some non-exclusive) versus dotted (exclusive) lines, which show that an exclusive relationship predicts values closer to one partner regardless of sexual trajectory (Color figure online)

Fig. 3

Prevalence of sex acts by sexual trajectory. Trajectory classes showed distinct prevalence of different sexual acts collapsed across time. The single and multiple classes reported more vaginal sex than did the rare partners class. Although there was a main effect of class on oral sex, pair-wise comparisons did not survive correction for multiple comparisons. The Multiple trajectory class reported the most anal sex, followed by the Single and Rare trajectories, with all means being significantly different in post hoc tests. Error bars are standard error of the mean