Global Inequalities in Female Breast Cancer Burden by Decomposition and Age-Period-Cohort Analysis, 1990-2021

Our objective was to analyze temporal trends and geographic disparities in the burden of female breast cancer from 1990 to 2021, focusing on age, period, cohort effects, and socioeconomic inequalities.

Using data from the 2021 Global Burden of Disease (GBD) study, we quantified disability-adjusted life years (DALYs) and deaths. Analyses included socio-demographic index (SDI) stratification, temporal decomposition, and an age-period-cohort (APC) model to estimate net drifts. The slope index of inequality (SII) and the concentration index were determined to measure cross-country inequalities, and a Bayesian APC model was used to predict the burden in 2050.

From 1990 to 2021, the DALYs and deaths associated with breast cancer increased worldwide, largely because of population growth and aging. Countries with high SDI values had the highest absolute burden, especially among older women, whereas burdens increased faster among younger groups in regions with low or low-middle SDI values. APC models revealed an increased risk in postmenopausal women and period-related decreases in high SDI countries. In contrast, risks increased or plateaued in low SDI regions. Cohort analysis revealed decreasing risks in high SDI countries but increasing risks in younger cohorts elsewhere. Furthermore, inequality shifted, with greater burdens in low SDI countries. Projections indicate continued global increases, especially after 2040.

The global burden of female breast cancer continues to increase with marked regional and age disparities, highlighting the urgent need for region-specific interventions, such as geriatric care in high SDI areas and improved access to screening and treatment in low SDI regions.