Objective To analyze the disease burden, temporal trends, and attributable risk factors of early-onset female breast cancer (EOBC) in China and globally from 1990 to 2021.

Methods Data on the absolute numbers and crude rates of incidence, mortality, and disability-adjusted life years (DALYs) for EOBC (diagnosis age < 50 years) in China and globally were extracted from the Global Burden of Disease (GBD) 2021 database. Attributable DALY proportions for five risk factors (smoking, alcohol use, physical inactivity, high red meat consumption, elevated fasting plasma glucose) and all combined risk factors were obtained. Joinpoint regression analysis was performed to assess temporal trends in age-standardized rates, quantified by annual percentage change (APC) and average annual percentage change (AAPC).

Results From 1990 to 2021, age-standardized incidence rates of EOBC increased significantly in both China (AAPC=2.25%) and globally (AAPC=0.64%; pairwise comparison, P < 0.001). In contrast, age-standardized mortality rates (China: AAPC=-0.82%; global: AAPC=-0.26%; P < 0.001) and DALY rates (China: AAPC=-0.63%; global: AAPC=-0.18%; P=0.004) showed overall declines. In 2021, China's age-standardized incidence and mortality rates were 13.49 and 1.99 per 100 000, respectively, compared to global rates of 13.61 and 3.14 per 100, 000. Notably, China's age-standardized mortality (APC=0.78% since 2014) and DALY rates (APC=1.38% since 2015) exhibited gradual upward trends in recent years. High red meat consumption accounted for the highest proportion of attributable DALYs for EOBC in both China (13.55%) and globally (11.20%) in 2021.

Conclusions China's age-standardized EOBC incidence is rising rapidly and approaching global levels, while mortality and DALY rates have increased over the past decade, underscoring persistent challenges in disease control. Future efforts should prioritize expanding the coverage of breast cancer screening programs, optimizing screening protocols, and enhancing public awareness of cancer prevention to mitigate the growing burden of EOBC in China.