Club Activity, Study Groups, and Academic Achievement: A Nationwide Study of Japanese Medical Students' Extracurricular Life.

Background: Student involvement in extracurricular activities (ECAs) possesses multiple benefits and has attracted substantial interest in medical education. Most studies on ECAs have been conducted in Western contexts, and findings on the association between ECAs and academic achievement are mixed. We examined the current status of ECA, particularly club activities and study groups, the most representative ECAs in Japan, among medical trainees. Methods: This was a nationwide cross-sectional study from April to May 2025 in Japan, using an online anonymous self-administered questionnaire. Potential participants were takers of the General Medicine In-Training Examination postgraduate "Year-0" (GM-ITE PGY-0). We asked the participants about their participation in club activities and study groups during their medical school life and evaluated their medical knowledge using their GM-ITE PGY-0 test score. The data were analyzed by descriptive statistics and multivariable linear regression analysis with adjustment for possible confounders. Results: We enrolled 437 of 748 medical trainees. 398 (91.1%) were involved in club activities, predominantly those involving music, while 156 (35.7%) participated in study groups, with clinical reasoning emerging as the most popular. On multivariable linear regression analysis, weekly or more frequent participation in club activities was associated with lower medical knowledge compared with no participation. In contrast, study group participation was positively and dose-dependently associated with medical knowledge test score. Conclusions: Medical schools should consider strategies to encourage academic ECAs such as study groups while promoting balanced engagement with nonacademic ECAs to optimize both their potential benefits and learning outcomes.