Intrapersonal and relationship characteristics: the importance of partner-specific measures in sexual health research

Collecting partner-specific data about multiple sexual partners is resource intensive. However, many variables that have been measured with generalized questions may, in fact, vary across different partnerships. Few studies have examined the need for data from all partners. The goal of this study was to examine if measuring intrapersonal and relationship constructs among high-risk individuals with multiple sexual partners benefitted from the use of partner-specific measures. We used data from a study that examined relationship dynamics among women and men aged 18–30 from the Los Angeles area. We assessed seven partner-specific measures of intrapersonal characteristics and relationship qualities/dynamics. We estimated multilevel mixed-effects linear regression models for each partner-specific outcome with random intercepts for individual participants and calculated the unconditional intraclass correlation (ICC). The similarity of partner-specific responses was very low or low for three measures (perceived vulnerability to HIV/STIs, relationship commitment, and relationship satisfaction); moderate for three measures (perceived vulnerability to pregnancy, sexual decision-making, and relationship power); and high for one measure (condom use self-efficacy). When studying populations with multiple sexual partners, relationship qualities are likely to vary across partners. In order to fully understand partnership dynamics, including influences on health behaviors, investing in partner-specific measurement is crucial.