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What Are the Major Risk Factors for Breast Cancer?

By BCRF | December 27, 2022

BCRF highlights the top known risk breast cancer risk factors for the disease based on research

We know that multiple risk factors contribute to a person’s overall breast cancer risk, and through research, we will potentially uncover more.

A risk factor is something that increases a person’s chance of getting a disease like breast cancer. Having a breast cancer risk factor—or several of them—doesn’t guarantee that you’ll be diagnosed in your lifetime: Some people with several risk factors never experience breast cancer, and others with no known risk factors get diagnosed with the disease every day.

Some risk factors for breast cancer are completely out of your control and can’t be changed. Others, particularly those associated with certain lifestyle choices, can. There’s no way to completely prevent breast cancer through lifestyle choices alone, and unfortunately, people can do everything “right” when it comes to controllable risk factors and still be diagnosed. But you may be able to reduce your risk of breast cancer by making certain healthy choices.

Below, we give an overview of what can increase a person’s risk of breast cancer according to research. To read about BCRF-supported research on risk, learn more here.

Major risk factors for breast cancer that you can’t control:

Age: Breast cancer risk increases with age, and most people diagnosed are over 50 years old.

Sex at birth: Although men can be diagnosed with breast cancer and one in 1,000 will be, the disease overwhelmingly impacts people who are born female.

Inherited gene mutations: Certain genetic mutations such as BRCA1, BRCA2, PALB2, CHEK2, and others can increase a person’s risk of breast cancer to varying degrees. A person with a BRCA1 mutation, for example, has an up to 72 percent chance of being diagnosed with breast cancer (compared to the average woman’s 13 percent risk).

Race and ethnicity: Based on current incidence rates, Black and white women are more likely to be diagnosed with breast cancer than Asian Americans, Pacific Islanders, Hispanic women, Latinas, and Native Americans. Race is also associated with a higher risk of certain types of breast cancer. Black women, for example, are more likely to be diagnosed with triple-negative breast cancer. Certain ethnic groups are also at a higher risk, such as Ashkenazi Jews, who have far higher rates of BRCA gene mutations than the general population.

Family history: Having first- and second-degree relatives on either side of your family who have been diagnosed with breast cancer can increase your risk.

Personal history: Previous experience with DCIS, invasive breast cancer, or another cancer can increase chances of being diagnosed with a new, different diagnosis. Radiation therapy, particularly when it’s given to children, teens, and younger adults with cancer, can also increase a person’s risk of a second diagnosis.

Breast density: Research has shown that breast density (more glandular and fibrous than fatty tissue) elevates your risk of breast cancer—partly because dense breasts are more difficult to screen (see how BCRF is aiming to improve screening here). The denser a person’s breasts the higher the risk: Women with more than 75 percent breast density have a four-to-six-fold increased risk, and BCRF research has shown there may be a correlation between breast density and family history.

Age at first menstrual period: Girls who get their periods before age 12 are at a slightly higher risk of breast cancer later in life, possibly because they have been exposed to estrogen and progesterone for longer.

Age at start of menopause: Similarly, women who begin menopause later—after 55—also have a slightly higher risk of breast cancer, likely because of longer hormone exposure.

Benign breast conditions: Certain non-cancerous breast conditions including fibroadenomas, cysts, hyperplasia, papilloma, and lobular carcinoma in situ (LCIS) can also increase risk.

Major risk factors for breast cancer that you can potentially control:

Weight: Studies have shown that excess weight and obesity—in childhood, adolescence, and after menopause—can elevate a woman’s risk of breast cancer later in life. Research has also shown that losing weight or avoiding future weight gain can decrease risk. Relatedly, exercise has been shown to not only help people lose weight or maintain a healthy weight but potentially reduce breast cancer risk.

Alcohol use: Alcohol consumption has been linked to cancer diagnoses and deaths. Even moderate use—one drink per day for women and up to two drinks a day for men—is associated with a higher risk of breast cancer and especially hormone receptor–positive disease. Women who drink more—consuming between two and three drinks per day—have a 20 percent higher risk of breast cancer over women who don’t drink.

Smoking: There’s no consensus that smoking increases a person’s risk of breast cancer specifically like there is for lung and other cancers, but according to the U.S. Surgeon General’s Office, evidence of a link between smoking and breast cancer is “suggestive but not sufficient.”

Timing of pregnancy: Decisions about pregnancy timing and whether to have children at all are highly personal, and there are no right and wrong answers. While giving birth later (after 30) or not having children can both increase a person’s breast cancer risk, it’s also important to acknowledge many different factors influence these choices.

Breastfeeding: Breastfeeding may offer a small protective benefit: For every 12 months a woman breastfeeds, her relative risk of breast cancer declined by about 4 percent.

Hormone use: Menopausal hormone therapy (MHT) increases users’ breast cancer risk (especially for HR-positive tumors) to varying degrees depending on years of use and whether the MHT is estrogen-only or estrogen and progesterone in combination. A woman taking estrogen and progesterone MHT for five to 14 years, for example, has double the breast cancer risk compared to a woman who didn’t use MHT. Comparatively, a woman taking estrogen-only MHT for the same amount of time sees a lower risk compared to non-users—but it’s important to note that only women who have had a hysterectomy can take estrogen-only MHT.

Oral hormone-based contraceptives may slightly increase risk, but some studies have shown no association and for many women, contraception’s benefits far outweigh risk.

Further Reading:
Selected References:

2014 SGR: The Health Consequences of Smoking—50 Years of Progress. (2021, June 2). Centers for Disease Control and Prevention.

Alcohol and Cancer Risk Fact Sheet. (2021, July 14). National Cancer Institute.

BRCA Gene Mutations: Cancer Risk and Genetic Testing Fact Sheet. (2020, November 19). National Cancer Institute.

Breast Cancer Prevention (PDQ®)–Health Professional Version. (2022, November 18). National Cancer Institute.

Breast Cancer Risk in American Women. (2020, December 16). National Cancer Institute.

Cancer of the Breast (Female) – Cancer Stat Facts. (n.d.). SEER.

Jewish Women and BRCA Gene Mutations | Bring Your Brave | CDC. (n.d.).

Second Cancers Related to Treatment. (n.d.).