Factors Linked to Breast Cancer Risk

Read our blog, Breast Cancer 101 – Understanding Risk Factors.

Some factors are linked to a small increased (or decreased) risk of breast cancer and others are linked to a larger increased (or decreased) risk.

Understanding which factors are linked to breast cancer risk can help you work with your health care provider to address any concerns you have and develop a breast cancer screening plan that’s right for you.

Our Breast Cancer Risk Factors Table compares risk factors by level of risk and strength of evidence. 

Factors linked to breast cancer risk are listed alphabetically below. Click on the topics below to learn more.

What is a risk factor?

Anything linked to a person’s chance of getting a disease is called a risk factor.

A risk factor can be related to:

• Genetics (such as family history)
• Lifestyle (such as exercise)
• Reproductive history (such as age at your first menstrual period)
• The environment (such as radiation exposure)

Cancer tends to be related to a combination of factors. Some things we may be able to control (such as exercise). Others are out of our control (such as age), and some are still unknown. Since many factors are linked to cancer risk and we can control only some of them, we can’t avoid some amount of risk.

Most breast cancer risk factors we have some control over are linked to only a small increase or decrease in risk. Because the disease process is so complex, it’s hard to know how a certain set of risk factors will work in any one person.

Where do the data come from?

Human studies

The data in this section come from 2 main types of research studies:

• Observational studies (cohort or case-control)
• Randomized controlled trials

The goal of these studies is to give information that helps support or disprove an idea about a possible link between an exposure (such as alcohol use) and an outcome (such as breast cancer) in people.

Although they have the same goal, observational studies and randomized controlled trials differ in:

• The way they’re conducted
• The strength of the conclusions they reach

Learn more about different types of research studies.

Animal studies

Animal studies add to our understanding of how and why some factors may be linked to cancer in people.

However, there are many differences between animals and people, so it’s hard to translate findings directly from one to the other.

Animal studies are also designed differently. They often look at exposures in larger doses and for shorter periods of time than are suitable for people.

While animal studies can lay the groundwork for research in people, we need human studies to draw conclusions for people.

All the data you see in this section of the website come from human studies.

Finding information on risk factors

Susan G. Komen® has up-to-date information on many established, probable and possible risk factors for breast cancer. Komen also has information on many factors not related to risk.

Other health organizations conduct research and/or prepare detailed summary reports of research on certain factors shown to have a link (or no link) to breast cancer and other types of cancer, including:

• International Agency for Research on Cancer (IARC)
• Centers for Disease Control and Prevention (CDC)  
• National Toxicology Program (NTP)  
• U.S. Food and Drug Administration (FDA)  
• World Cancer Research Fund International

IARC is a part of the World Health Organization. The CDC, NTP and FDA are all part of the U.S. Department of Health and Human Services. World Cancer Research Fund International is a non-profit organization.

To learn more about the role of the environment in breast cancer, Susan G. Komen® sponsored a study from the National Academies of Sciences, Engineering, and Medicine (formerly the Institute of Medicine), “Breast Cancer and the Environment, a Life Course Approach.”

SUSAN G. KOMEN®‘S BREAST SELF-AWARENESS MESSAGES

1. Know your risk Talk with both sides of your family to learn about your family health history. Talk with a health care provider about your risk of breast cancer. 2. Get screened Talk with a health care provider about which screening tests are right for you if you’re at higher risk. Have a mammogram every year starting at age 40 if you’re at average risk.* Have a clinical breast exam at least every 3 years starting at age 25, and every year starting at age 40.* * Per National Comprehensive Cancer Network Guidelines 3. Know what is normal for you See a health care provider if you notice any of these breast changes: Lump, hard knot or thickening inside the breast or underarm area Swelling, warmth, redness or darkening of the breast Change in the size or shape of the breast Dimpling or puckering of the skin Itchy, scaly sore or rash on the nipple Pulling in of the nipple or other parts of the breast Nipple discharge that starts suddenly New pain in one spot that doesn’t go away To see illustrations of these warning signs, please visit the Warning Signs of Breast Cancer page. 4. Make healthy lifestyle choices Maintain a healthy weight. Make exercise part of your routine. Limit alcohol intake. Limit menopausal hormone therapy (postmenopausal hormone use). Breastfeed if you can.

Updated 12/20/24

This content is regularly reviewed by an expert panel including researchers, practicing clinicians and patient advocates.