Declining antibiotic consumption and changing sexually transmitted infection dynamics in Japan: a national ecological time-series analysis, 2013-2024.

Publication date: May 16, 2026

We examined whether declining antibiotic consumption in Japan coincided with changes in sexually transmitted infection (STI) indicators. We conducted a national ecological time-series analysis using annual data from 2013 to 2024. Antibiotic consumption was measured as defined daily doses per 1,000 inhabitants per day. Outcomes were syphilis from all-case surveillance and chlamydia and gonorrhea from sentinel surveillance. Log-linear regression models with appropriate offsets estimated incidence rate ratios (IRRs) per 10% increase in antibiotic consumption. Sensitivity analyses excluded the COVID-19 pandemic period. Overall antibiotic consumption declined substantially during the study period, whereas syphilis notifications increased markedly. Chlamydia increased gradually, and gonorrhea fluctuated. In primary analyses, a 10% increase in antibiotic consumption was associated with lower incidence of chlamydia (IRR 0. 964, 95% CI 0. 949-0. 978) and gonorrhea (0. 836, 0. 758-0. 922). The association with syphilis was imprecise and not statistically significant (0. 836, 0. 643-1. 087). Sensitivity analyses excluding 2020-2022 yielded similar directional findings. Declining antibiotic consumption coincided with changes in some STI indicators in Japan, but associations were heterogeneous across infections. These ecological findings are hypothesis-generating and require further evaluation using more granular data.

Semantics

Original Article