Rich diets, decreasing family size, delayed childbearing, reduced breastfeeding, and increased obesity and alcohol consumption have contributed to the increasing incidence of breast cancer. The main reasons for the rise in incidence: 1. Estrogen use The global rise in breast cancer incidence has been linked to the excessive use of estrogen, which is increasingly used because of changes in fertility and diet. 2. Prolonged menstrual status Improved nutrition means that girls reach puberty earlier and women go through menopause later. One hundred years ago, the age of first menstruation for girls was 16 or 17, but now it is more likely to be 12 to 13 years old. For every year that menopause is delayed, the risk of breast cancer increases by 3% 3. Fertility Factors More and more women are going out to work, resulting in late births, fewer births, and only a few women breastfeeding. for every year that childbirth is delayed around the age of 25, the risk of breast cancer increases by 3%. The more children a woman has, the lower her risk of breast cancer, so the current trend of smaller families is increasing the risk of breast cancer for many women. For every unit of alcohol consumed per day, the risk of breast cancer increases by 7%. The incidence of breast cancer varies greatly around the world. The number of people diagnosed with breast cancer in Japan is 1/5 of that in the U.S. However, Japanese women who move to the U.S. soon face the same risks as American women. Since the 1970s, the incidence of breast cancer in the UK has increased by 84%.