Distant Family History
Breast cancer in more distant relatives can slightly raise your breast cancer risk. These may include aunts, grandmothers and cousins. This risk is not nearly as high as when the cancer is found in a first-degree relative.
Hormone Replacement Therapy (HRT)
Long-term use of estrogen and progesterone raises the risk of breast cancer. These hormones are used as hormone replacement therapy, or HRT. The level of risk returns to normal after stopping HRT for five years or more.
Previous Benign Breast Biopsy
Women who had a biopsy showing any of the following have a slightly higher risk:
- Solid, noncancerous breast tumors (fibroadenomas) with complex features
- Hyperplasia without atypia
- Sclerosing adenosis
Early Menstruation and Late Menopause
Women who began menstruating before age 12 are at a higher risk. Women who went through menopause after the age of 55 face a slightly higher risk.
Delayed Childbirth or Not Having Children
Having your first child after age 35 or never having children puts you at slightly higher risk. The reason may be because you are exposed to more estrogen and progesterone over your lifetime.
Drinking more than seven alcoholic drinks a week has been linked to a higher risk of breast cancer. This is particularly true for women under age 30. Women who drink more than one alcoholic drink a day have a slight increase in risk. Those who consume two to five drinks each day have about 1.5 times the risk of women who drink no alcohol. For these women, reducing alcohol intake can help to lower the risk.
Dense breast tissue may slightly increase the risk for breast cancer. Dense tissue can also make the cancer more difficult to detect on mammograms.
The insulin resistance associated with diabetes is believed to raise the risk of breast cancer.
An inactive lifestyle, particularly before age 40, may increase your breast cancer risk. Regular exercise can reduce the risk.
Exposure to some chemicals and pesticides may increase the risk for cancer in general. The level of this risk is not well understood.
Other Cancer in the Family
A family history of certain cancers may increase the risk of breast cancer. This includes cancer of the:
Women descended from Eastern and Central European Jews (Ashkenazi) may be at higher risk. This is because changes in BRCA1 and BRCA2 genes are more common in this population
Changes in the BRCA genes are also more common in certain other ethnic groups. This includes French Canadians and those from Iceland.
Caucasian women are at a slightly higher risk of developing breast cancer. However, women of color (i.e., African-American and Latinos) under 40 are more likely to develop breast cancer than Caucasian women under 40.