The occurrence of breast cancer may be related to estrogen in the body, which can act as a proliferative agent on the breast epithelium, and thus the following conditions may be related to the timing of estrogen action 1. Menstrual period. Women who have their first menstruation before the age of 13 or who have not stopped menstruating by the age of 50 are prone to breast cancer because of the long duration of estrogen’s action on the breast; 2. Marital status. Single unmarried women are more prone to breast cancer than married women, and the older they are, the more pronounced this tendency is; women who marry late or have no children after marriage have a higher incidence of breast cancer than those who have had children; 3. The risk of breast cancer is higher in women who have not breast-fed after childbirth and have not had a full-term birth at the age of 35 or 40. 4. Hormones. The occurrence of breast cancer is closely related to the level of estrogen, and high level of growth hormone is also a contributing factor to breast cancer. Long-term supplementation of exogenous hormones, common hormonal drugs such as oral contraceptives or cosmetics may increase the risk of breast cancer. 5. Heredity and family history. Heredity and family history of breast cancer is one of the risk factors for breast cancer. Women with a family history of breast cancer have a significantly higher chance of developing breast cancer than those without a family history of breast cancer. 6. Diet. High fat, high protein and high calorie diet increases the risk of breast cancer. People who are obese or consume too much fat are prone to breast cancer. 7. Medical history. Atypical hyperplasia of the breast may progress to breast cancer, and a history of unilateral breast cancer can make the incidence of the opposite side two to five times higher than normal. If you have had breast cancer on one side, the chance of having cancer on the opposite side is higher than the chance of not having cancer. 8. Smoking and staying up late. Active or passive smokers have a higher incidence of breast cancer. Women who have reached menopause and have ever smoked have a 3-fold increased risk of breast cancer compared to those who have never actively and passively smoked. Smoking in postmenopausal women is not associated with breast cancer incidence, but premenopausal women who smoke or passively smoke have a 2.6-fold increased risk of developing breast cancer. Some studies have shown that staying up late often increases the risk of breast cancer. 9. Obesity and exercise. Endogenous estrogen is one of the causes of breast cancer. Obesity affects hormone levels, and studies have shown that postmenopausal women who gain weight or increase their body mass index are at increased risk of breast cancer. Exercise may reduce the risk of breast cancer, especially in women who have given birth. Most breast cancers occur in women between the ages of 40 and 60, or around the time of menopause, with the highest incidence especially between the ages of 45 and 49 and 60 and 64.