Breast density is a risk factor for breast cancer. This study explored distribution of mammographic density quantitatively and qualitatively in a wide age range of Taiwanese women. Subjects with negative and benign mammographic findings were included. According to the Breast Imaging Reporting and Data System, the proportion of extremely dense breasts declined from 58.0% in women < 30 years to 1.9% in women > 74 years. More than 80% of mammograms in women < 55 years old were classified as extremely or heterogeneously dense, while the proportion of dense breasts was still high in women aged 60-64 years (59.3%). The absolute dense area of the breast declined from 35.8% in women < 30 years to 18.5% in women > 74 years. The correlation between breast density and age was significant, with and without controlling for the effect of body composition (p < 0.001), implying that the relationship between breast density and age was not wholly related to body composition. In conclusion, the higher breast density in Taiwanese women aged 60-64 years was comparable to that of Western women aged 40-44 years in the literature. This suggests that breast cancer screening using mammography may be more challenging for Asian women than for Western women of the same age.
Keywords: age; breast composition; mammographic density; mammography.