{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T06:10:27Z","timestamp":1792131027335,"version":"4.4.0"},"reference-count":29,"publisher":"BMJ","issue":"4","license":[{"start":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T00:00:00Z","timestamp":1776211200000},"content-version":"unspecified","delay-in-days":14,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100009023","name":"Precursory Research for Embryonic Science and Technology","doi-asserted-by":"publisher","award":["JPMJPR23R1"],"award-info":[{"award-number":["JPMJPR23R1"]}],"id":[{"id":"10.13039\/501100009023","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open"],"accepted":{"date-parts":[[2026,3,20]]},"published-print":{"date-parts":[[2026,4]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>To examine trends and demographic characteristics of syphilis incidence in Japan using a large nationwide claims database with family linkage, with particular focus on differences by sex, age, HIV status and family relationships.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Design<\/jats:title>\n                    <jats:p>Retrospective cohort study.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Setting<\/jats:title>\n                    <jats:p>JMDC claims database (JMDC Inc, Tokyo, Japan), a nationwide administrative claims database in Japan, using data from 2016 to 2023.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Participants<\/jats:title>\n                    <jats:p>Individuals aged 16\u201359 years enrolled in the JMDC database, including employees of medium-to-large companies and their dependents (n=12.5\u2009million).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Outcome measures<\/jats:title>\n                    <jats:p>Syphilis cases were defined by International Classification of Diseases, 10th Revision (ICD-10) codes (A50\u2013A53) with concurrent treatment with relevant antibiotics. We determined syphilis incidence rates per 100\u2009000 person-years, stratified by sex, age, HIV status and family relationships. We also investigated within-couple concordance patterns and reinfection rates.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Among 16.4\u2009million individuals, 9357 syphilis infections were identified among 8881 individuals. Incidence increased markedly during the pandemic, reaching 48.2 (men) and 12.9 (women) per 100\u2009000 person-years in 2023. Men showed consistently high incidence in their 20s\u201350s, whereas female incidence peaked in the 10s\u201320s. Among 2\u2009294\u2009184 married couples, dependent women (ie, housewives) showed comparably high incidence to age-matched men (10\u201320 per 100\u2009000 person-years). In 1286 couples with at least one syphilis case, 12.4% of wives in their 20s were also diagnosed, compared with 2%\u20133% in older groups. In 20s couples, the proportion of syphilis among wives only and husbands only was similar. Subgroup analysis revealed notably high incidence among unmarried female dependent youths (2022: 66.7 per 100\u2009000 person-years). Individuals living with HIV had substantially elevated incidence (3000\u201315\u2009000 per 100\u2009000 person-years) and reinfection rates.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Using a large claims database with family linkage, we found that while male syphilis incidence remained dominant, high rates were also observed among dependent women and youths. These findings suggest that syphilis risk may extend beyond traditionally recognised high-risk populations and emphasise the need for targeted screening and preventive strategies in broader demographic groups.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjopen-2025-114337","type":"journal-article","created":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T16:40:54Z","timestamp":1776271254000},"page":"e114337","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Trends and characteristics of syphilis incidence in Japan: a nationwide claims-based analysis of working-age populations and their dependents, 2016\u20132023"],"prefix":"10.1136","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1677-3369","authenticated-orcid":false,"given":"Kazuhiko","family":"Ikeuchi","sequence":"first","affiliation":[{"name":"Department of Infectious Diseases, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kazuya","family":"Okushin","sequence":"additional","affiliation":[{"name":"Department of Infection Control and Prevention, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"},{"name":"Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuki","family":"Arisato","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Toshiyuki","family":"Kishida","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shinya","family":"Matsumoto","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"},{"name":"Department of Infection Control and Prevention, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Akira","family":"Kado","sequence":"additional","affiliation":[{"name":"Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"},{"name":"Division for Health Service Promotion, The University of Tokyo, Bunkyo-ku, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hiroshi","family":"Yotsuyanagi","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases and Applied Immunology, IMSUT Hospital, The University of Tokyo Institute of Medical Science, Minato-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Takeya","family":"Tsutsumi","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"},{"name":"Department of Infection Control and Prevention, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"239","published-online":{"date-parts":[[2026,4,15]]},"reference":[{"key":"2026041509403164000_16.4.e114337.1","doi-asserted-by":"publisher","DOI":"10.1016\/s0140-6736(22)02348-0"},{"key":"2026041509403164000_16.4.e114337.2","doi-asserted-by":"publisher","DOI":"10.1001\/jama.2014.13259"},{"key":"2026041509403164000_16.4.e114337.3","doi-asserted-by":"publisher","DOI":"10.1172\/JCI57173"},{"key":"2026041509403164000_16.4.e114337.4","doi-asserted-by":"publisher","DOI":"10.1001\/jama.290.11.1510"},{"key":"2026041509403164000_16.4.e114337.5","unstructured":"World Health Organization . Syphilis. 2025. Available: https:\/\/www.who.int\/news-room\/fact-sheets\/detail\/syphilis [Accessed 9 Oct 2025]."},{"key":"2026041509403164000_16.4.e114337.6","doi-asserted-by":"crossref","DOI":"10.3390\/microorganisms13020285","article-title":"The Rise of Syphilis Infections and Reinfections over a Decade (2009-2019) in the Bolognese Area: A Retrospective Analysis","volume":"13","author":"Gaspari","year":"2025","journal-title":"Microorganisms"},{"key":"2026041509403164000_16.4.e114337.7","article-title":"The changing epidemiology of syphilis: new strategies for new challenges in China","volume":"65","author":"Cao","year":"2025","journal-title":"Lancet Reg Health West Pac"},{"key":"2026041509403164000_16.4.e114337.8","unstructured":"Notification Trends Among Syphilis Cases in Japan . Division of infectious disease epidemiology research; center for public health action in applied epidemiology; and department of bacteriology I. 2025. 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Population estimates by age (five-year age groups) and sex \u2013 total population. 2025. 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Labor market heterogeneity and welfare consequences in Japan","volume":"59","author":"Kikuchi","year":"2021","journal-title":"J Jpn Int Econ"},{"key":"2026041509403164000_16.4.e114337.25","doi-asserted-by":"crossref","DOI":"10.1016\/j.jjie.2023.101256","article-title":"COVID-19 and the employment gender gap in Japan","volume":"68","author":"Fukai","year":"2023","journal-title":"J Jpn Int Econ"},{"key":"2026041509403164000_16.4.e114337.26","doi-asserted-by":"crossref","DOI":"10.1017\/S0950268823001772","article-title":"Injection drug use and sexually transmitted infections among men who have sex with men: A retrospective cohort study at an HIV\/AIDS referral hospital in Tokyo, 2013-2022","volume":"151","author":"Ikeuchi","year":"2023","journal-title":"Epidemiol Infect"},{"key":"2026041509403164000_16.4.e114337.27","doi-asserted-by":"publisher","DOI":"10.1016\/j.jiac.2022.07.017"},{"key":"2026041509403164000_16.4.e114337.28","doi-asserted-by":"crossref","DOI":"10.1186\/s12889-026-26209-7","article-title":"Health and social inequities among cisgender gay and bisexual men in Japan: a nationwide cross-sectional study using a large-scale web-based survey","volume":"26","author":"Ikeuchi","year":"2026","journal-title":"BMC Public Health"},{"key":"2026041509403164000_16.4.e114337.29","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pmed.1001885","article-title":"The REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) statement","volume":"12","author":"Benchimol","year":"2015","journal-title":"PLoS Med"}],"container-title":["BMJ Open"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.1136\/bmjopen-2025-114337","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,15]],"date-time":"2026-04-15T16:40:58Z","timestamp":1776271258000},"score":1,"resource":{"primary":{"URL":"https:\/\/bmjopen.bmj.com\/lookup\/doi\/10.1136\/bmjopen-2025-114337"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4]]},"references-count":29,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,4,15]]},"published-print":{"date-parts":[[2026,4]]}},"alternative-id":["10.1136\/bmjopen-2025-114337"],"URL":"https:\/\/doi.org\/10.1136\/bmjopen-2025-114337","relation":{},"ISSN":["2044-6055","2044-6055"],"issn-type":[{"value":"2044-6055","type":"print"},{"value":"2044-6055","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4]]}}}