Breast Cancer Risk Factors: What Increases Your Risk?

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

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 are diagnosed with the disease every day.

The most significant risk factors for breast cancer include age, sex at birth, inherited gene mutations (such as BRCA1 and BRCA2), family history, and high breast density. Other lifestyle factors can also play a role, such as alcohol use, excess body weight (particularly after menopause), certain forms of menopausal hormone therapy, and reproductive and menstrual history.

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 modifiable 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 research tells us about the things that can increase a person’s risk of breast cancer.

Uncontrollable risk factors for breast cancer

While some risk factors for breast cancer are simply beyond your control, knowing about them can help you make more informed decisions about screening, monitoring, and preventive care.

Biological and Demographic Factors

These factors are rooted in your biology. Research has consistently identified some population groups at higher risk of breast cancer.

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.

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. However, breast cancer rates are rising faster in Asian Americans than in any other racial or ethnic group in the U.S. 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.

Genetic and Family Factors

Your DNA and family history can significantly shape your breast cancer risk—and in some cases, an inherited gene mutation can dramatically increase the likelihood of a diagnosis.

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 lifetime risk of 13 percent).

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 because of certain hereditary factors.

Personal history: Previous diagnoses of DCIS, invasive breast cancer, or another cancer can increase chances of developing a new, different cancer. 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 Tissue Factors

The physical composition of your breast tissue is something many people don’t think about—but it can actually influence breast cancer risk.

Breast density: Research has shown that having dense breasts (more glandular and fibrous than fatty tissue) elevates your risk of breast cancer—partly because dense breasts are more difficult to screen. 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. The only way to know if you have dense breasts is by getting a mammogram.

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

What are the risk factors for breast cancer by age?

Hormonal exposure across a woman’s life can also influence her overall breast cancer risk, specifically when menstruation begins and when menopause ends.

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 as well.

Breast cancer risk factors you can control

While no lifestyle choice can guarantee you won’t develop breast cancer, certain factors within your control can influence your overall risk—and making informed choices is one of the most proactive things you can do.

Weight, Diet, and Exercise

Body weight, diet, and exercise are closely connected—and research suggests that together, they can be meaningful levers for reducing breast cancer risk.

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. Learn more about the connection between diet and breast cancer and how nutrition plays a role in managing risk. Relatedly, exercise has been shown to not only help people lose weight or maintain a healthy weight but potentially reduce breast cancer risk.

Substance Use

Research has linked certain substances to increased breast cancer risk, though the strength of that evidence varies.

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, especially hormone receptor (HR)-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: Studies indicate that current smokers have a higher risk of developing breast cancer compared to lifetime non-smokers, with estimates varying across studies depending on duration and intensity of smoking.

Reproductive and Hormonal Factors

Lifetime hormonal exposure—shaped by menstrual history, pregnancy, breastfeeding, and hormone-based medications—can also play a role in breast cancer risk.

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. Giving birth later (after 30) or not having children can both increase a person’s breast cancer risk because each could mean a longer exposure to estrogen. But a person’s breast cancer risk is determined by a combination of factors and not just these choices.

Breastfeeding: Did you know that breastfeeding may offer a small protective benefit? For every 12 months a woman breastfeeds, her relative risk of breast cancer declines by about 4 percent.

Hormone use: Hormone replacement therapy (HRT), also known as menopausal hormone therapy (MHT) increases users’ breast cancer risk, especially for HR-positive tumors. But the degree of increase varies depending on years of use and whether the HRT is estrogen-only or estrogen in combination with progesterone. A woman taking estrogen and progesterone HRT for five to 14 years, for example, has double the breast cancer risk compared to a woman who didn’t. Comparatively, a woman taking estrogen-only HRT 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 generally take estrogen-only HRT.

Oral hormone-based contraceptives may slightly increase risk, but the absolute increase is small and some studies have shown no association. For many women, the benefits (contraception, reduced ovarian and endometrial cancer risk, menstrual health) outweigh the modest risk.

Understanding Your Breast Cancer Risk

Breast cancer risk is not a single number or a single factor. It’s the product of many variables working together, some of which you were born with and some of which shift over a lifetime. Having risk factors doesn’t mean a diagnosis is inevitable and not having them doesn’t mean you’re in the clear. What matters most is staying informed, keeping up with recommended screenings, and having an honest conversation with your doctor about your personal risk profile.

If you’re concerned about your breast cancer risk, a formal risk assessment can help clarify your picture and guide decisions about screening frequency, preventive options, and monitoring. BCRF-funded researchers are working every day to improve how we identify, assess, and reduce risk—so that one day, prevention will be within everyone’s reach.

Every dollar raised by BCRF goes toward the scientists and studies that are changing what we know about breast cancer risk, detection, and prevention. Your support helps fund that progress—and brings us closer to a world where fewer people face this disease at all. Donate, start a fundraiser, or explore more ways to give today.