Global, Regional, and National Burden of Breast Cancer Attributable to Low Physical Activity in Women of Reproductive Age: Historical Trends from 1990 to 2021 and Projections to 2035

Background: This study analyzes the global patterns and trends of breast cancer attributable to low physical activity (LPA) among women of reproductive age (1990–2021) using Global Burden of Disease (GBD) data, providing quantitative evidence for prioritizing physical-activity interventions to reduce LPA-attributable breast-cancer burden, specifically among women of reproductive age. Methods: This study used data from the GBD Study 2021. We analyzed the changes in the burden of LPA-related breast cancer in women of reproductive age at the global, regional, and national levels from 1990 to 2021. The Bayesian age-period-cohort (BAPC) model was used to predict future trends. Decomposition analysis using Das Gupta’s framework explored the factors driving changes in LPA-attributable breast-cancer burden among reproductive-age women. Results: From 1990 to 2021, in high sociodemographic index (SDI) regions, deaths and disability-adjusted life years (DALYs) of breast cancer in women of reproductive age attributable to LPA showed a decreasing trend, with corresponding estimated annual percentage change (EAPC) values of -1.20 (95% CI: -1.29, -1.10) and -1.05 (95% CI: -1.14, -0.96), respectively. Globally, deaths increased by 68% and DALYs by 69% between 1990 and 2021, while low-SDI countries showed the steepest relative rise in age-standardized mortality (EAPC=1.04, 95 % CI: 0.83–1.25) and DALY rates (EAPC=1.08, 95 % CI: 0.87–1.29). Decomposition analysis indicated that population growth was the main driver of the increasing global breast cancer burden. The BAPC model predicted that from 2022 to 2035, the global burden of breast cancer in women of reproductive age attributable to LPA would continue to rise, with age-standardized mortality rates (ASMRs) projected to increase by 7.1 % (to 0.15 per 100,000) and age-standardized DALY rates (ASDRs) by 4.2 % (to 7.3 per 100,000 ) by 2035. Conclusion: Globally, the burden of breast cancer in women of reproductive age attributable to LPA has shown an increasing trend, with significant regional disparities. Our findings underscore the importance of physical activity in controlling the burden of breast cancer among reproductive-age women.