Author(s): FUKUSHIMA, K., NAKATA, Y., NAGAO, M., AKAGI, R., OTOMO, M., DOHI, M., Institution: JAPAN INSTITUTE OF SPORTS SCIENCES, Country: JAPAN, Abstract-ID: 1667

INTRODUCTION:
Sport-related concussion (SRC) in professional women's football is increasingly monitored, yet evidence from Japan remains limited. Incidence and median time-loss describe frequency and typical recovery, but season-level impact may be underestimated when rare prolonged recoveries inflate cumulative time-loss. Injury burden (days lost per exposure) may therefore better reflect team-level consequences. This study described SRC incidence, time-loss, and injury burden across two seasons in Japanese professional women's football and examined how an exceptionally prolonged case influenced burden estimates.
METHODS:
Prospective injury surveillance was conducted during the 2022 and 2023 seasons among participating league teams with complete exposure recording. Match and training exposure were measured as player-hours. SRC events were recorded when diagnosed by qualified medical staff, in accordance with contemporary consensus definitions. Incidence rates were calculated per 1,000 player-hours with exact 95% Poisson confidence intervals (CI). Time-loss was defined as the days from injury to full return to unrestricted participation. Injury burden was calculated as the total days lost per 1,000 player-hours. A sensitivity analysis was performed, excluding one case in 2023 with exceptionally prolonged time-loss (554 days).
RESULTS:
Total exposure was 24,449 player-hours in 2022 (match 2,238; training 22,211) and 29,342 in 2023 (match 3,062; training 26,280). Four SRCs occurred in 2022 and nine in 2023. Overall incidence was 0.16 per 1,000 player-hours (95% CI, 0.04–0.41) in 2022 and 0.31 (0.14–0.58) in 2023. Match incidence exceeded training incidence in both seasons (2022: match 0.89 [0.11–3.22] vs training 0.09 [0.01–0.33]; 2023: match 0.98 [0.20–2.86] vs training 0.23 [0.08–0.50]), all per 1,000 player-hours. Median time-loss was 9.5 days (interquartile range [IQR], 8–17.5; range 7–24) in 2022 and 9.0 days (IQR, 5–11.5; range 5–554) in 2023. Overall injury burden in 2023 was 21.03 days lost per 1,000 player-hours; excluding the single 554-day case, the burden decreased to approximately 2.15 days lost per 1,000 player-hours (about 63 total days lost over 29,342 player-hours).
CONCLUSION:
Concussion incidence was comparable to rates reported in elite women’s club football (approximately 0.2 per 1,000 hours) [1]. In Japanese professional women’s football, typical time-loss was about one week and incidence was higher during matches than training. However, injury burden was highly sensitive to rare prolonged recoveries, indicating that a single severe case can substantially increase season-level impact despite stable median time-loss. Reporting injury burden alongside incidence and time-loss may better capture team-level consequences and support medical planning and return-to-play management in professional women’s football.

References
1. Hallen A, et al. Br J Sports Med 2024;58:128-135.