Association between mammographic breast density and lifestyle in japanese women

A high mammographic breast density is considered to be a risk factor for breast cancer. However, only a small number of studies on the association between breast density and lifestyle have been per- formed. A cross-sectional study was performed using a survey with 29 questions on life history and lifestyle. The breast density on mammography was classified into 4 categories following the BI-RADS criteria. The subjects were 522 women with no medical history of breast cancer. The mean age was 53.3 years old. On multivariate analysis, only BMI was a significant factor determining breast density in premenopausal women (parameter estimate, 0.403; p value, 0.0005), and the density decreased as BMI rose. In postmenopausal women, BMI (parameter estimate, 0.196; p value, 0.0143) and number of deliveries (parameter estimate, 0.388; p value, 0.0186) were significant factors determining breast density; breast density decreased as BMI and number of deliveries increased. Only BMI and number of deliveries were identified as factors significantly influencing breast density. BMI was inversely cor- related with breast density before and after menopause, whereas the influence of number of deliveries on breast density was significant only in postmenopausal women in their 50 and 60s.