What are the risk factors for breast cancer?

Having even several of these risk factors doesn't mean you'll get breast cancer. There are different types of risk factors. Some you can't do anything about, such as your age, genes and gender. Others, like drinking alcohol and watching your weight, are risk factors over which you have some measure of control.

If you have concerns about your own risk factors, discuss them with your physician.


  • gender
  • age
  • genes
  • family history
  • personal history of breast cancer
  • ethnicity
  • dense breast tissue
  • certain precancerous breast conditions
  • previous chest radiation
  • exposure to radiation
  • recent oral contraceptive use
  • post-menopausal hormone therapy
  • alcohol use
  • being overweight or obese
  • exposure to certain carcinogens
  • lack of physical activity
  • exposure to secondhand smoke
Dr. Audrey K. Chun, MD
Geriatric Medicine Specialist

Unfortunately, the most significant risk factors for breast cancer are beyond our control, such as gender, age, family history and genetics. However, a study that analyzed data from more than 85,000 postmenopausal women suggests that regular exercise may be associated with a reduced risk, along with maintaining a normal body weight and consuming less alcohol, regardless of whether you have a family history of breast cancer.

The research on lifestyle behaviors and breast cancer risk is very vague; some data does support lifestyle choices as risk factors, while other studies do not. However, there is convincing data on alcohol; heavy drinking, at any age, is a risk factor for breast cancer development. I advise a common-sense approach. Getting regular exercise, eating healthy and avoiding obesity provide many health benefits.

Risk factors for breast cancer include:

  • Family history: Hereditary breast cancers account for approximately 5 to 10 percent of all breast cancers. While having a first-degree relative with breast cancer increases a woman's chances, specific predispositions for breast cancer, such as inheriting a mutation in either the BRCA1 or BRCA2 gene, can raise breast cancer risk to 80 percent. Women of Ashkenazi Jewish heritage are about five times more likely than other women to have a BRCA gene mutation. Women who have tested positive for either of the BRCA genes may want to discuss options for risk reduction, including surgical removal of the ovaries (if premenopausal), bilateral mastectomy or use of the drug tamoxifen.
  • Estrogen exposure: Because estrogen fuels breast cell growth, the longer your ovaries were producing estrogen, the greater your risk of breast cancer. Menstruation before age 12, menopause after 55, pregnancy after 35 or no pregnancies at all mean greater estrogen exposure. Postmenopausal hormone therapy also adds to the risk.
  • Breast history: Dense breast tissue on mammograms, which can indicate a propensity for tissue to proliferate, is associated with increased risk, as are prior breast biopsies, especially those that revealed precancerous changes, such as lobular carcinoma in situ. Previous treatment for breast cancer also raises the risk of another cancer.
  • Radiation therapy: Chest radiation to treat cancer increases the lifetime risk, especially if delivered during puberty. In women who have a BRCA gene mutation, the risk is amplified, especially by chest x-rays received before age 20.
  • Obesity: Probably because estrogen is produced by body fat in addition to the ovaries, obesity raises the risk of breast cancer, especially after menopause.
  • Alcohol use: Alcohol has also been shown to increase circulating estrogen levels, so breast cancer risk increases with every drink taken. Although the risk is slight for women who limit their daily consumption to one drink, it mounts steadily with greater intake.
  • Lack of exercise: Growing evidence is implicating inactivity as a contributing factor.

Being a woman is the greatest risk factor for breast cancer. While men can and do develop breast cancer, there are only about 1,000 new cases of male breast cancer diagnosed annually in the United States—1 percent of all breast cancers. Age, as well as family, personal and reproductive history, may also affect a woman's chance of developing breast cancer.

  • Age: The risk of developing breast cancer increases with age. About 80 percent of all breast cancers occur in women over the age of 50. The disease is uncommon in women under the age of 35.
  • Family history: A woman whose mother, sister or daughter has had breast cancer is at higher risk. The risk is increased if the family member's cancer affected both breasts or was diagnosed before menopause. That's when a form of breast cancer that tends to run in families is more common. Women who carry certain inherited genes are at higher risk than other women of developing breast cancer in their lifetime. The most common genes identified so far are BRCA 1 and BRCA 2, but there are some less common genes, and others are being studied. This "hereditary" type of breast cancer accounts for approximately 5 to 10 percent of all breast-cancer cases.
  • Personal history: Women who have had breast cancer in one breast, or who have had certain types of benign (noncancerous) breast disease—such as atypical cells on a breast biopsy—are also at greater risk.
  • Reproductive history: The risk of breast cancer is slightly greater among women who started their periods before age 12, who went through menopause after the age of 50 or who did not have children before the age of 30.
Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)

Here are some factors that increase breast cancer risk:

  • Having a family history of breast cancer
  • Being taller than 5 feet 7 inches
  • Getting your first period younger than 11, or older than 15
  • Having a first child when older than 35, or younger than 20
  • Currently using birth control pills
  • Using hormone replacement therapy for more than five years
  • Of Jewish ancestry
  • Drinking more than one alcoholic drink a day
  • Having a BMI greater than 27
  • Testing positive for the BRCA1 or BRCA2 gene mutation
  • Having a history of atypical hyperplasia, a type of benign breast disease

Here are some factors that decrease breast cancer risk:

  • Breastfeeding for one year or more
  • Eating a diet that includes monounsaturated fats instead of saturated fats
  • Performing more than three hours of physical activity a week
  • Birthing more than two children
  • Taking drugs that block estrogen (tamoxifen and raloxifene)
  • Taking the vitamin folate if you are a moderate alcohol drinker

Breast cancer risk is higher among women whose close blood relatives have this disease. Having one first-degree relative (mother, sister or daughter) with breast cancer approximately doubles a woman's risk. Having two first-degree relatives increases her risk about five-fold.

Altogether, about 20 to 30 percent of women with breast cancer have a family member with this disease. This means that most (70 to 80 percent of) women who get breast cancer do not have a family history of this disease. And certainly not all women with a family history get breast cancer.

Dr. Stuart A. Linder, MD
Plastic Surgeon

Increased breast-cancer risk factors include:

  1. Age. The older a woman is, especially once over age 60, the greater the risks for breast cancer.
  2. Race. Some studies have shown that African American women may have an increased risk over women of other ethnic backgrounds.
  3. Family history. Family history of breast cancer is a strong indicator of increased risk. If your mother, sister or daughter has breast cancer, there is an increased and more significant chance that you may as well.
  4. Personal history. If you have had a history of breast cancer, there is a greater risk that you may develop it again. There are breast cancer genes that have been shown to increase the risk of cancer as well.
  5. Estrogen. Estrogen is a hormone that occurs in every woman, but at increased levels it may also increase your risk of breast cancer. Increased estrogen situations can include a) having your first period at an early age—before the age of twelve; b) a pregnancy occurring at a later age, after the age of thirty-five; c) having no children, as women who have never been pregnant have increased levels of estrogen throughout their lives; d) taking hormonal replacement therapy; and e) taking oral contraceptives.
  6. Lifestyle changes. These may also increase and/or reduce your risk of cancer. Decreasing your fat intake, increasing your fiber, limiting alcohol, reducing smoking and staying active can all significantly reduce your risk of cancers of the breasts.
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Risk factors for breast cancer include older age, early age of first menstrual period and first pregnancy at an older age or never becoming pregnant. Prolonged use of estrogen replacement medications also increases risk, but birth control pills are not a risk factor. Genetics play a role as well, and there is increased risk if a first degree relative (parent, brother, sister, child) has breast cancer.

Breast cancer is the most common cancer in women. Every woman is at some risk for breast cancer, but there are many factors that can make one woman's risk differ from others.

Risk factors for breast cancer include:

  • Growing older
  • Personal history of breast cancer
  • Breast cancer in the family (especially mother, daughter or sister)
  • Abnormal breast exams or mammograms in the past
  • No children or having children at a late age
  • Eating a diet high in fat or being overweight
  • Prolonged exposure to estrogen (early onset of period, late menopause, long-term birth control, estrogen therapy)

Although the cause of breast cancer is typically unknown, researchers have identified risk factors that make some women more prone to developing it. Hormones are among those factors. Research indicates that breast cancer risk increases when breast tissue is exposed to high levels of hormones for long periods. This can be due to beginning menstruation at an early age, experiencing menopause at a late age, having children later in life or not at all. Studies also indicate that long-term use of birth control methods that contain both estrogen and progestin, a synthetic form of progesterone and long-term use of hormone replacement therapy may increase breast cancer risk slightly. However, the risk from birth control hormones disappears 10 years after stopping usage.

Nonhormonal risk factors include: family history of breast cancer; biopsy-confirmed atypical hyperplasia or atypical lobular hyperplasia; mutation in the BRCA1 or BRCA2 genes; family history of BRCA1 or BRCA2 mutations; radiation to the chest before age 40; lobular carcinoma in situ; and certain other inherited syndromes and genes. You may also be at higher risk if you smoke, drink heavily or are obese.

Eric Olsen
Fitness Specialist

Because more women are living longer, it's not surprising that more women are at risk of breast cancer. But there are other factors in addition to age at work as well.

Family history of the disease is a significant and unfortunately unmodifiable risk factor. Thus, a woman is at a much higher risk if her mother or a sister has had breast cancer, and she'll want to be very careful to change other risk factors that can be modified.

Alcohol consumption may also increase the risk. A high-fat diet is thought to be a factor, though Willet Walter's study with nurses says otherwise. Women in countries such as Japan, where they consume much less dietary fat, have a significantly lower risk of breast cancer than American women. Japanese women who move to this country and who, over time, adopt more American-style eating and other habits eventually come to have the same risk as other American women.

Being overweight is also associated with an increased risk of breast cancer, particularly in the menopausal years. Because obesity can be a result of both diet and activity patterns, dietary changes to reduce fats will also likely reduce calories consumed.

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Some common risk factors for breast cancer include the following:

  • Gender - Although nearly 2,000 men will be diagnosed with breast cancer each year, breast cancer is 100 times more common in women. The National Cancer Institute estimates that over 190,000 women will be diagnosed with breast cancer annually.
  • Aging - On average, women over 60 are more likely to be diagnosed with breast cancer. Only about 10 to 15 percent of breast cancers occur in women younger than 45. However, this may vary for different races or ethnicities.
  • Obesity - After menopause, fat tissue may contribute to increases in estrogen levels, and high levels of estrogen may increase the risk of breast cancer. Weight gain during adulthood and excess body fat around the waist may also play a role.
  • Inherited Factors - Some inherited genetic mutations may increase your breast cancer risks. Mutations in the BRCA1 and BRCA2 genes are the most common inherited causes. Other rare mutations may also make some women more susceptible to developing breast cancer. Gene testing reveals the presence of potential genetic problems, particularly in families that have a history of breast cancer.
  • Family History - Having a family history of breast cancer, particularly women with a mother, sister or daughter who has or had breast cancer, may double the risk.
  • Not Having Children - Women who have had no children, or who were pregnant later in life (over age 35) may have a greater chance of developing breast cancer. Breast-feeding may help to lower your breast cancer risks.

Other factors that may affect your risk of developing breast cancer include the following:

  • Having abnormal breast cells (found by looking through a microscope)
  • High breast density
  • Certain breast changes
  • Using oral contraceptives within the past 10 years
  • Starting menstruation at an early age (before age 12) and/or menopause at an older age (after age 55)
  • Combined post-menopausal hormone therapy (PHT)
  • Maintaining a sedentary lifestyle
  • Heavy drinking
  • Radiation exposure
  • Previous use of DES (a drug commonly given to pregnant women from 1940 to 1971)

NOTE: Anything that increases your risk of getting a disease is called a risk factor. Having a breast cancer risk factor does not mean that you will get cancer. Not having risk factors doesn’t mean that you will not get cancer. If you think you may be at risk, you should discuss it with your doctor.

Here are some risk factors for breast cancer that cannot be changed:

  • Gender: Being a woman is the leading risk factor for developing breast cancer. The chance of a woman developing invasive breast cancer sometime during her life is just under one in eight.
  • Aging: Risk of developing breast cancer increases as women age.
  • Menstrual periods: Women who have had more menstrual cycles because they started menstruating at an early age (before age 12) and/or went through menopause at a later age (after age 55) have a slightly higher risk of breast cancer.
  • Genetics: Between 5 and 10 percent of breast cancer cases are thought to be hereditary.
  • Family history: Breast cancer risk is higher among women whose close blood relatives have the disease.
  • Personal history: Women with cancer in one breast have a three- to four-fold increased risk of developing cancer in the other breast or in another part of the same breast.
  • Race and ethnicity: Caucasian women are slightly more likely than African American women to develop breast cancer, but African American women are more likely to die of breast cancer. Asian, Hispanic and Native American women have a lower risk of developing and dying from breast cancer.
  • Dense breast tissue: Women with dense breasts have more glandular tissue and less fatty tissue and are at higher risk of breast cancer. Dense tissue and tumors have similar density, so tumors can be harder to detect in women with denser breasts.
  • Benign breast conditions: Women diagnosed with certain benign breast conditions may have an increased risk of breast cancer. Benign conditions include: Non-proliferative (non-spreading) lesions; Proliferative (spreading) lesions without atypia; Proliferative (spreading) lesions with atypia.
  • Lobular carcinoma in situ (LCIS): Women with LCIS have a 7- to 11-fold increased risk of developing cancer in either breast.
  • Previous chest radiation: Women who had radiation therapy to the chest area as treatment for another cancer (such as Hodgkin's disease or non-Hodgkin's lymphoma), especially before the age of 30, are at significantly increased risk for breast cancer.
  • Diethylstilbestrol (DES) exposure: From the 1940s through the 1960s, some pregnant women were given DES because it was thought to lower their chances of miscarriage. These women have a slightly increased risk of developing breast cancer. Women whose mothers took DES during pregnancy may also have a slightly higher risk of breast cancer.
Dr. Cary H. Hsu, MD

The risk factors for breast cancer have been well identified through population studies. Reproductive, hormonal and other factors include the following:

  • early menarche (the age you begin menstruation)
  • no children or giving birth after the age of 30
  • older age of menopause
  • postmenopausal hormone replacement treatment
  • higher socioeconomic status, as there is a higher likelihood of hormone use
  • diet plays a relatively smaller role, but obesity predisposes one to breast cancer because fat cells produce estrogen
  • alcohol use in excess
  • people who had ionizing radiation at a young age have an increased risk of breast cancer eight years after this therapy

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.