{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,21]],"date-time":"2026-10-21T00:52:58Z","timestamp":1792543978691,"version":"4.5.0"},"reference-count":40,"publisher":"BMJ","issue":"1","license":[{"start":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T00:00:00Z","timestamp":1771459200000},"content-version":"unspecified","delay-in-days":49,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open Sport Exerc Med"],"accepted":{"date-parts":[[2026,1,27]]},"published-print":{"date-parts":[[2026,1]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>To explore the epidemiology, incidence and distribution of sports-related concussion (SRC) among middle- and high-school students from Japan sustained during extracurricular sports.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      We conducted a retrospective observational analysis of the Injury and Accident Mutual Aid Benefit System database from April 2012 to March 2020. Cases of SRC diagnosed by healthcare providers were extracted, with club membership numbers obtained from external sources to calculate sport-specific incidence per 1000 members. Data were stratified by sex, school type, grade, injury timing and sport. Statistical analyses included the \u03c7\n                      <jats:sup>2<\/jats:sup>\n                      test and descriptive statistics.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Among over 8 million injuries, 12 158 SRC cases were identified. Of these, 11 660 cases occurred across 24 sports based on available membership data. Boys accounted for 84% of SRCs in these 24 sports, with the highest rates in contact sports. Second-year students in both middle and high school were most affected. Rugby exhibited the highest SRC incidence (8.10 per 1000 members), followed by judo and karate, highlighting traditional Japanese martial arts as previously under-recognised high-risk activities. Concussions were more frequent in competition (49%) than in training (44%), particularly in contact sports. SRC incidence rose from 2012, peaking in the late-2010s (0.28\/1000 in middle school; 0.82\/1000 in high school).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>SRC risk varied by sex, grade and sport, with contact sports and traditional martial arts showing an elevated incidence. These findings underscore the need for targeted concussion prevention, education and safety guideline revisions for high-risk groups. Further research should explore sport-specific risk factors to enhance prevention.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjsem-2025-002943","type":"journal-article","created":{"date-parts":[[2026,2,19]],"date-time":"2026-02-19T13:20:17Z","timestamp":1771507217000},"page":"e002943","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":1,"title":["Epidemiology of sport-related concussions among middle- and high-school students in Japan: a nationwide analysis using insurance registry data"],"prefix":"10.1136","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-2004-628X","authenticated-orcid":false,"given":"Kazutaka","family":"Fukushima","sequence":"first","affiliation":[{"name":"Department of Sport Medicine, Japan Institute of Sports Sciences, Kita, 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