Changes in sexual behaviors, network attributes, and STI testing among 15–44-year-olds by marital/cohabiting status and partner number: National Survey of Family Growth, 2008-19

BACKGROUND: Relationships and recent sexual experience can impact sexual behaviors, networks, and STI testing. How they affect trends in these factors and increasing STI rates is understudied. METHODS: We analyzed data from 28,027 females and 23,479 males ages 15-44 from the National Survey of Family Growth, 2008-2010 through 2017-2019. We used survey-weighted linear or logistic regression to evaluate linear trends in self-reported sexual behaviors with opposite-sex partners; sexual network attributes; and STI testing, stratified by sex and, separately, by marital/cohabiting status and number of past-year vaginal sex partners (1 vs. ≥ 2). Trends p < 0.050 reported below. RESULTS: From 2008-2019, condom use at last vaginal sex decreased among never-married females (51.9% in 2008-10 to 42.9% in 2017-19), never-married males (61.9%-56.3%), and individuals with ≥2 partners (females = 45.3%-34.9%; males = 54.0%-45.7%). Mean number of vaginal sex acts in past 4 weeks decreased among cohabiting females (9.46-7.40), never-married males (4.11-3.40), and males with 1 partner (7.25-6.62). The proportion of never-married females reporting sex with males with male partner(s) increased from 2.5% to 5.1%; similarly, percentages of never-married males (3.8%-5.5%) and males with ≥2 partners (4.6%-6.3%) reporting sex with males increased. Racial/ethnic homophily with current vaginal sex partners decreased among cohabiting females (86.5%-80.4%) and married and never-married males (married = 88.9%-85.9%; never-married = 81.2%-72.3%). Past-year chlamydia testing increased among females who were married (13.0%-17.1%), previously-married (27.6%-45.8%), or had 1 partner (21.7%-25.4%). CONCLUSIONS: Changes in sexual behaviors, network attributes, and STI testing from 2008-2010 through 2017-2019 varied by marital/cohabiting status and number of past-year opposite-sex partners in complex ways, most commonly among never-married females and males and males with multiple partners. While these changes' combined potential impact on STI transmission is uncertain, understanding trends in sexual behaviors, networks, and testing by marital/cohabiting status and partner number can contextualize their contributions to the STI epidemic and support sexual health services tailoring and prioritization.