Modeling the impact of changing sexual behaviors with opposite-sex partners and STI testing among women and men ages 15–44 on STI diagnosis rates in the United States 2012–2019

Objective

To estimate the potential contributions of reported changes in frequency of penile-vaginal sex (PVS), condom use and STI screening to changes in gonorrhea and chlamydial diagnoses from 2012 to 2019.

Methods

An agent-based model of the heterosexual population in the U.S. simulated the STI epidemics. Baseline was calibrated to 2012 diagnosis rates, testing, condom use, and frequency of PVS. Counterfactuals used behaviors from the 2017-2019 NSFG, and we evaluated changes in diagnosis and incidence rates in 2019.

Results

Higher testing rates increased gonorrhea and chlamydia diagnosis by 14% and 13%, respectively, but did not reduce incidence. Declining frequency of PVS reduced the diagnosis rate for gonorrhea and chlamydia 6% and 3% respectively while reducing incidence by 10% and 9% respectively. Declining condom use had negligible impact on diagnosis and incidence.

Conclusion

Understanding how changing behavior drives STI incidence is essential to addressing the growing epidemics. Changes in testing and frequency of PVS likely contributed to some, but not all, of the changes in diagnoses. More research is needed to understand the context within which changing sexual behavior and testing are occurring.