Identification of key risk factors for syphilis among high-risk populations in urban areas of Japan.

INTRODUCTION

We aimed to identify high-risk factors for syphilis infection in metropolitan areas, specifically Tokyo, to guide effective strategy development against syphilis epidemics.

METHODS

From July 20, 2023, to January 26, 2024, a REDCap survey was administered to individuals tested for syphilis at three Tokyo clinics. Consent was obtained through an agreement option at initiation of the questionnaire permitting individuals to decline participation. By selecting the consent option and completing the survey, individuals agreed to participate in the study. This research was supported by a Ministry of Health, Labor and Welfare research grant (JPMH23HA2011) and approved by the Kochi University School of Medicine Ethics Committee (Approval No. 2023-44).

RESULTS

A total of 215 participants were analyzed after excluding 13 from the initial cohort. Of these, 48.4 % tested positive for syphilis. Positive cases were more frequently individuals with a history of sexually transmitted infections (STIs) undergoing their first syphilis test. Symptoms strongly correlated with syphilis positivity (60.5 % among symptomatic participants). Multivariate analysis identified casual sexual relationships and a history of STIs as significant risk factors for syphilis positivity. The presence of symptoms was also significantly associated with syphilis positivity. Engagement in sex work and anal intercourse trended toward increased risk. Age, men having sex with men, and use of matchmaking apps exhibited no significant association.

CONCLUSION

This study identified risks related to sexual partners, sex industry involvement, and sexual activities. Promoting preventive measures among sex industry workers and patrons is crucial. Increased syphilis testing opportunities may aid in reducing disease prevalence.