1. Advancing age
2. Female gender (breast cancer occurs 100 times more frequently in women than in men),
3. White race (highest rate of breast cancer occurs among white women, although breast cancer remains the most common cancer among women of every major ethnic group),
4. Weight and body fat (A higher BMI and/or perimenopausal weight gain have been consistently associated with a higher risk of breast cancer among postmenopausal women although an increased BMI is associated with a lower risk of breast cancer in premenopausal women),
5. Tall stature ( In one study, women who were >175 cm (69 inches) tall were 20 percent more likely to develop breast cancer than those <160 cm (63 inches) tall),
6. Estrogen levels (High endogenous estrogen levels increase the risk of breast cancer),
7. Earlier menarche and later menopause (Early age at menarche is associated with a higher risk of breast cancer. In addition, later age at menopause increases breast cancer risk),
8. Nulliparity (Nulliparous women are at increased risk for breast cancer compared with parous women),
9. Increasing age at first full term pregnancy ( Women who become pregnant later in life have an increased risk of breast cancer),
10. Personal history of breast cancer ( A personal history of ductal carcinoma in situ (DCIS) or invasive breast cancer increases the risk of developing an invasive breast cancer in the contralateral breast),
11. Family history of breast cancer (The risk associated with a positive family history of breast cancer is strongly affected by the number of female first-degree relatives with and without cancer and the age at diagnosis),
12. Alcohol (Alcohol consumption is associated with an increased risk of breast cancer development),
13. Smoking (Although results have not been uniform, multiple studies suggest there is a modestly increased risk of breast cancer in smokers),
14. Night shift work (Night-shift work is recognized by the International Agency for Research on Cancer and the World Health Organization as a probable carcinogen, although evidence is mixed).
It is sometimes frustrating to be confronted with a myriad of risk factors, some of which are out of our control. The good news is that there are some demonstrated protective factors that reduce the risk of breast cancer. These include:
1. Breast feeding (A protective effect of breastfeeding has been shown in multiple case-control and cohort studies and meta-analyses),
2. Physical activity (regular physical exercise appears to provide modest protection against breast cancer, particularly in postmenopausal women).
And several factors have been identified that do not influence breast cancer risk, including: abortion, tubal ligation, caffeine, cosmetic breast implants, electromagnetic fields, electric blankets, and hair dyes – these have not been associated with breast cancer risk.