ObjectiveTo analyze the age distribution characteristics of breast cancer incidence and mortality across countries and regions worldwide, and to explore the association between the human development index (HDI) and the average age of onset and death of breast cancer, to provide a scientific basis for developing breast cancer prevention and control strategies. MethodsData on female breast cancer incidence and mortality for 185 countries and regions worldwide were obtained from the GLOBOCAN 2022 database, which released by the International Agency for Research on Cancer. This study systematically analyzed the distribution characteristics of the age of onset and death of breast cancer in China and different regions of the world with different levels of HDI and different geographical regions, and explored the relationship between HDI and the average age of onset and death of breast cancer. ResultsIn 2022, there were approximately 2.30 million new cases of female breast cancer worldwide, with an age-standardized incidence rate of 46.80 per 100 000, and approximately 665 300 deaths, with an age-standardized mortality rate of 12.64 per 100 000. The incidence rate was highest in very high HDI regions (75.63 per 100 000), while the mortality rate was highest in low HDI regions (19.11 per 100 000). The average age of breast cancer incidence globally was 58.7 years, and the average age of death was 63.2 years. Both the average age of onset and death of breast cancer increased with the improvement of HDI levels. Specifically, in low HDI regions, the average age of incidence was 51.0 years, and the average age of death was 53.7 years; whereas in very high HDI regions, the average age of breast cancer incidence reached 62.7 years, and the average age of death was 70.0 years. The average age of breast cancer incidence and death in China was slightly lower than the global average level, at 56.0 years and 62.7 years, respectively. From different regions, developed areas such as European regions, North America, and Australia / New Zealand had a relatively higher average ages of incidence, exceeding 61 years; whereas in less-developed areas such as various African regions (excluding South Africa) and Armenia had relatively lower average ages of incidence, as low as under 53 years, especially with the average age of incidence in Central Africa being as low as 50.6 years. The HDI showed a significant positive correlation with both the average age of incidence and death, with correlation coefficients of 0.77 and 0.82, respectively (P<0.001). After adjusting for population age structure, the correlation between the age-standardized average age of incidence and death and HDI slightly decreased, with correlation coefficients of 0.41 and 0.73, respectively (P<0.001). ConclusionsThere were significant regional differences in the age distribution of breast cancer incidence and mortality worldwide, which are closely associated with HDI level. High-HDI regions have a high incidence rates but relatively low mortality rate, while low-HDI regions face a double burden of earlier onset and higher mortality. The age onset of breast cancer in Chinese women is earlier than that in European and American countries, and there are significant regional differences in the age distribution of incidence and mortality compared to other countries. Therefore, the development of prevention and control strategies such as screening should consider the characteristics of breast cancer incidence and mortality distribution by age in China.