Osamu Ishida, Shotaro Yoshida, Koji Tsutsumi
BACKGROUND: Despite the increasing number of female medical graduates in Japan, women remain underrepresented in cardiovascular surgery. METHODS: Using complete registry data from the Japanese Board of Cardiovascular Surgery (2004-2025), we examined annual proportions of female board-certified cardiovascular surgeons and newly certified surgeons. Linear regression was performed to assess trends and extrapolate future proportions. International benchmarking utilized published data from the United States, Europe, and global surveys. RESULTS: = 0.973; P < 0.001). Among newly certified surgeons, the proportion was more variable, reaching 9.0% in 2025. Linear extrapolation projected the overall proportion to reach 5.6% in 2030 (95% prediction interval 5.0-6.1%) and 7.6% in 2040 (95% prediction interval 7.0-8.2%). The current Japanese proportion of 4.8% is approximately half the global average of 8.0% (from the 2024 EACTS global workforce analysis based on CTSNet data across 146 countries) and 42-47% of the United States (11.5%) and Europe (10.3%) in the same report. CONCLUSIONS: Over two decades, female representation in Japanese cardiovascular surgery has risen steadily to 4.8%, driven by increasing female new certifications. Japan's current level corresponds to Western proportions from the mid-2000s, reflecting a persistent international disparity. The recent physician work-style reform and ongoing efforts to improve retention may influence future trends, but longitudinal data are needed to evaluate their impact.