Factors That Affect Breast Cancer Risk

Some factors affect breast cancer risk a great deal and others by only a small amount.

Understanding which factors may affect your risk of breast cancer 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 that affect breast cancer risk are listed below alphabetically.

Age is a risk factor for breast cancer in both women and men. The older a person is, the more likely they are to get breast cancer.

Learn more about age and breast cancer risk.  

Both the age when a woman gives birth to her first child and the number of children a woman has affect her risk of breast cancer.

Women who give birth to their first child at age 35 or younger tend to get a protective benefit from pregnancy [6-11].

In general, the more children a woman has given birth to, the lower her risk of breast cancer tends to be [6-11].

Learn more about age at first childbirth, number of childbirths and breast cancer risk.

Starting menstrual periods at a young age is linked to a small increase in breast cancer risk [10,14-18].

For example, women who begin their periods before age 11 have about a 15-20 percent higher breast cancer risk compared to those who begin their periods at age 15 or older [17].

Learn more about age at first period and breast cancer risk.

Going through menopause at a later age is linked to an increased risk of breast cancer [10,15,18,20].

For example, women who go through menopause after age 55 have about a 40 percent higher risk of breast cancer than women who do so at age 45 or younger [17].

Learn more about age at menopause and breast cancer risk.

Drinking alcohol is linked to an increased risk of breast cancer [21].

For example, women who have 2-3 alcoholic drinks per day have about a 20 percent higher risk of breast cancer than women who don’t drink alcohol [21].

Learn more about alcohol and breast cancer risk.

Learn about alcohol and breast cancer survival.

Anti-Müllerian hormone (AMH) is produced in the ovaries. It’s important in the development of reproductive organs.

Women with higher blood levels of AMH may have a higher risk of breast cancer compared to women of the same age who have lower levels of AMH [389-392].

Learn more about AMH hormone levels and breast cancer risk.

In the U.S., Jewish women have a slightly higher risk of breast cancer than other women [27].

This increased risk is likely due to the high prevalence of BRCA1 and BRCA2 inherited gene mutations in Jewish women of Eastern European descent (Ashkenazi Jews).

Learn more about Ashkenazi Jewish heritage, BRCA1/2 inherited gene mutations and breast cancer risk.

Being born female is the main risk factor for breast cancer. Although men can get breast cancer, it’s about 100 times more common in women [35].

Learn more about being born female and breast cancer risk.

Learn more about breast cancer in men.

Current or recent use of birth control pills is linked to a slight increase in breast cancer risk [10,36-39].

For example, women who take birth control pills (or recently used them) have a 20-30 percent higher risk of breast cancer than women who’ve never used the pill [35,38-39].

Learn more about birth control pills and breast cancer risk.

Learn about other types of contraceptives that contain hormones (including Depo Provera, the birth control patch and the vaginal ring) and breast cancer risk.

Women with a higher birthweight (a woman’s weight when she was born) have an increased risk of breast cancer, especially before menopause [48-53].

Learn more about birthweight and breast cancer risk.

Learn more about early life exposures and breast cancer risk

Androgens (such as testosterone) are natural hormones. They are important in sexual development.

Higher amounts of androgens in the blood may be linked to an increased risk of breast cancer in women [59-62].

Learn more about blood androgen levels and breast cancer risk.

Estrogens are natural hormones. They are important in sexual development and other body functions.

After menopause, higher amounts of estrogen in the blood are linked to an increased risk of breast cancer in women [19].

Researchers are studying a possible link to breast cancer before menopause.

Learn more about blood estrogen levels and breast cancer risk.

Being overweight or obese affects the risk of breast cancer differently before and after menopause.

  • Before menopause, women who are overweight or obese have a modestly decreased risk of breast cancer [66-70].
  • After menopause, women who are overweight or obese have an increased risk of breast cancer [66-68,70].

Gaining weight in adulthood is linked to an increased risk of breast cancer before and after menopause [80-84].

Learn more about body weight, weight gain and breast cancer risk.

Learn about body weight and breast cancer survival

Women with high bone density have about a 60-80 percent higher risk of breast cancer compared to women with low bone density [102].

Learn more about bone density and breast cancer risk

Breast density is a measure used to describe the proportion of the different tissues that make up a woman’s breasts. It compares the area of breast and connective tissue seen on a mammogram to the area of fat.

Women with dense breasts are 4-5 times more likely to get breast cancer than women with fatty breasts [104-105].

Learn more about breast density and breast cancer risk.

Women who breastfeed have a lower risk of breast cancer than women who don’t, especially before menopause [11,18,115-118].

Learn more about breastfeeding and breast cancer risk.

Women who get regular exercise (physical activity) have about a 10-20 percent lower risk of breast cancer than women who are not active [126-132].

Learn more about exercise and breast cancer risk.

Learn about exercise and breast cancer survival.

People with a family history of breast, ovarian cancer or prostate cancer have an increased risk of breast cancer. The increased risk is likely due to genetic factors but may also be due to shared lifestyle factors or other family traits.

Learn more about a family history of breast, ovarian or prostate cancer and breast cancer risk.

Learn more about inherited gene mutations and breast cancer risk.  

Fruits and vegetables

Eating vegetables may be linked to a lower risk of some breast cancers [160-162]. Eating fruits may also be linked to a lower breast cancer risk [159].

Carotenoids

Carotenoids are natural orange-red food pigments found in fruits and vegetables (like melons, carrots and sweet potatoes). Beta-carotene is an example of a carotenoid.

Women with higher blood levels of carotenoids have a reduced risk of breast cancer compared to women with lower levels of carotenoids [167].

Learn more about fruits, vegetables, carotenoids and breast cancer risk.  

Taller women have a higher risk of breast cancer than shorter women [10,66,90,175-182].

Learn more about height and breast cancer risk

Benign breast conditions (also called benign breast diseases) are non-cancerous breast disorders.

Some benign breast conditions are linked to an increased risk of breast cancer and others are not. For example, women who have hyperplasia have an increased risk of breast cancer [183-187].

Learn more about hyperplasia and other benign breast conditions and breast cancer risk.

Learn more about different types of benign breast conditions.  

Insulin-like growth factor 1 (IGF-1) is a natural hormone that plays a role in growth and development.

Women with higher levels of IGF-1 in the blood may have a higher risk of breast cancer than women with lower levels of IGF-1 [249-253].

Learn more about IGF-1 and breast cancer risk.

Some inherited gene mutations have been linked to breast cancer.

These include mutations in the following genes (in alphabetical order):

  • ATM
  • BARD1
  • BRIP1
  • BRCA1
  • BRCA2
  • CDH1
  • CHEK2
  • NBN
  • NF1
  • PALB2
  • PTEN
  • RAD51C
  • RAD51D
  • STK11
  • TP53

Other genes are under study and may also play a role in breast cancer.

Learn more about inherited gene mutations and breast cancer risk.

Find information for people who have a BRCA1 or BRCA2 inherited gene mutation.

Women who routinely work night shifts for many years have a small increased risk of breast cancer [254-256]. One possible reason for the increased risk among these workers is their exposure to light at night.

More research is needed to understand which aspects of shift work may impact breast cancer risk.

Learn more about light at night, shift work and breast cancer risk

When abnormal cells grow inside the lobules of the breast, but have not spread to nearby tissue or beyond, the condition is called lobular carcinoma in situ (LCIS).

Although the term LCIS includes the word “carcinoma,” LCIS is not invasive breast cancer. However, LCIS increases the risk of invasive breast cancer.

Compared to women without LCIS, those with LCIS are 7-11 times more likely to develop invasive breast cancer [259-260].

Learn more about LCIS and breast cancer risk

Menopausal hormone therapy (MHT) is FDA-approved for the short-term relief of menopausal symptoms [268]. MHT is also called postmenopausal hormone therapy and hormone replacement therapy (HRT).

The main types of MHT are:

  • Estrogen plus progestin
  • Estrogen alone

Women who use estrogen plus progestin MHT have an increased risk of breast cancer [20,269-273].

Some studies have shown women who use estrogen alone may also have an increased risk of breast cancer [20,271-273]. However, one large study found these women had a decreased risk [276].

MHT is not usually given to women who’ve been treated for breast cancer because it may be linked to an increased risk of recurrence [279-280].

Learn more about MHT and breast cancer risk

Learn more about MHT and breast cancer recurrence.  

Women who’ve had breast cancer in the past have a higher risk of getting a new breast cancer compared to women who’ve never had breast cancer [281-283].

Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer. Women who’ve had DCIS in the past have an increased risk of DCIS recurrence and an increased risk of invasive breast cancer [292-299].

A personal history of Hodgkin’s disease, ovarian cancer and certain other cancers may be also linked to an increased risk of breast cancer [28,155,300-306].

Learn more about a personal history of breast cancer or other cancers and breast cancer risk.  

Prolactin is a natural hormone that plays a role in breast growth and the production of milk during breastfeeding.

Women with higher blood levels of prolactin have a slightly higher risk of breast cancer than women with lower levels [308-309].

Learn more about prolactin and breast cancer risk

Rates of breast cancer in the U.S. vary by race and ethnicity.

White women and Black women have the highest incidence of breast cancer (rate of new breast cancer cases) overall [317]. American Indian and Alaska Native women have the lowest incidence [317].

Learn more about race, ethnicity, and breast cancer risk.

People exposed to large amounts of radiation early in life, such as radiation treatment to the chest area for childhood cancer, have an increased risk of breast cancer [302-303,310-311].

For example, women treated with radiation therapy to the chest area for Hodgkin’s at a young age have about 3-7 times the risk of breast cancer compared to women who had Hodgkin’s disease at a young age, but were never treated with radiation therapy [302].

People exposed to very low doses of radiation (such as from X-rays) don’t have much, if any, increase in breast cancer risk [232,312-313].

Learn more about radiation treatment in youth and breast cancer risk.

Learn more about radiation exposure from mammography and other medical imaging and breast cancer risk.

Learn about occupational exposure to radiation and breast cancer risk.

Women who smoke for many years appear to have a slightly increased risk of breast cancer [500,504,533-540].

Women who are current smokers and have been smoking for more than 10 years appear to have about a 10 percent higher risk of breast cancer than women who’ve never smoked [504,535,538].

Learn more about smoking and breast cancer risk.

Learn about smoking and breast cancer survival.

Updated 03/01/21

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