Breast Cancer Risk Factors

Breast Cancer Risk and Risk Factors

You may be familiar with the statistic that says 1 in 8 women will develop invasive breast cancer. Many people misinterpret this to mean that, on any given day, they and the women they know have a 1-in-8 risk of developing the disease. That’s simply not true.

In reality, about 1 in 8 women in the United States — 12%, or about 12 out of every 100 — can expect to develop breast cancer over the course of an entire lifetime. In the U.S., an average lifetime is about 80 years. So, it’s more accurate to say that 1 in 8 women in the U.S. who reach the age of 80 can expect to develop breast cancer. In each decade of life, the risk of getting breast cancer is actually lower than 12% for most women.

People tend to have very different ways of viewing risk. For you, a 1-in-8 lifetime risk may seem like a high likelihood of getting breast cancer. Or you may turn this around and reason that there is a 7-in-8, or 87.5%, chance you will never get breast cancer, even if you live to age 80. How you view risk often depends on your individual situation — for example, whether you or many women you know have had breast cancer, or you have reason to believe you are at higher-than-normal risk for the disease — and your usual way of looking at the world.

Even though studies have found that women have a 12% lifetime risk of developing breast cancer, your individual risk may be higher or lower than that. Individual risk is affected by many different factors, such as family history, reproductive history, lifestyle, environment, and others.

Breast Cancer Risk Factors

A “risk factor” is anything that increases your risk of developing breast cancer. Many of the most important risk factors for breast cancer are beyond your control, such as age, family history, and medical history. However, there are some risk factors you can control, such as weight, physical activity, and alcohol consumption.

Be sure to talk with your doctor about all of your possible risk factors for breast cancer. There may be steps you can take to lower your risk of breast cancer, and your doctor can help you come up with a plan. Your doctor also needs to be aware of any other risk factors beyond your control, so that he or she has an accurate understanding of your level of breast cancer risk. This can influence recommendations about breast cancer screening — what tests to have and when to start having them.

Risk Factors You Can Control

Weight.

Being overweight is associated with increased risk of breast cancer, especially for women after menopause. Fat tissue is the body’s main source of estrogen after menopause, when the ovaries stop producing the hormone. Having more fat tissue means having higher estrogen levels, which can increase breast cancer risk.

Diet.

Studies are looking at the relationship between diet and breast cancer risk and the risk of recurrence. The Women's Health Initiative Trial suggested that a diet very low in fat may reduce the risk of breast cancer. More research is needed in this important area for women who are interested in eating well to reduce their risk of ever getting breast cancer.

In the meantime, here's what dietitians suggest:

• Keep your body weight in a healthy range for your height and frame. Body mass index, though not a perfect measurement, can help you estimate your healthy weight.

• Eat plenty of vegetables and fruit (more than 5 cups a day).

• Try to limit your saturated fat intake to less than 10% of your total calories per day and limit your fat intake to about 30 grams per day.

• Eat foods high in omega-3 fatty acids.

• Avoid trans fats, processed meats, and charred or smoked foods.

You'll find that processed foods generally don't fit in this type of diet as well as fresh foods do. For more information, visit our page on healthy eating to reduce risk of breast cancer in the Nutrition section.

Exercise.

Evidence is growing that exercise can reduce breast cancer risk. The American Cancer Society recommends engaging in 45-60 minutes of physical exercise 5 or more days a week. (See our Fitness Guide)

Alcohol consumption.

Studies have shown that breast cancer risk increases with the amount of alcohol a woman drinks. Alcohol can limit your liver’s ability to control blood levels of the hormone estrogen, which in turn can increase risk.

Smoking.

Smoking is associated with a small increase in breast cancer risk.

Exposure to estrogen.

Because the female hormone estrogen stimulates breast cell growth, exposure to estrogen over long periods of time, without any breaks, can increase the risk of breast cancer. Some of these risk factors are under your control, such as:

• taking combined hormone replacement therapy (estrogen and progesterone; HRT) for several years or more, or taking estrogen alone for more than 10 years

• being overweight

• regularly drinking alcohol

Recent oral contraceptive use.

Using oral contraceptives (birth control pills) appears to slightly increase a woman’s risk for breast cancer, but only for a limited period of time. Women who stopped using oral contraceptives more than 10 years ago do not appear to have any increased breast cancer risk.

Stress and anxiety.

There is no clear proof that stress and anxiety can increase breast cancer risk. However, anything you can do to reduce your stress and to enhance your comfort, joy, and satisfaction can have a major effect on your quality of life. So-called “mindful measures” (such as meditation, yoga, visualization exercises, and prayer) may be valuable additions to your daily or weekly routine. Some research suggests that these practices can strengthen the immune system. (See our resources on Positive Thinking, Meditation and Affirmations)

Risk Factors You Cannot Control

Gender.

Being a woman is the most significant risk factor for developing breast cancer. Although men can get breast cancer, too, women’s breast cells are constantly changing and growing, mainly due to the activity of the female hormones estrogen and progesterone. This activity puts them at much greater risk for breast cancer.

Age.

Simply growing older is the second biggest risk factor for breast cancer. From age 30 to 39, the risk is 1 in 228, or .44%. That jumps to 1 in 29, or just under 3.5%, by the time you are in your 60s.

Family history of breast cancer.

If you have a first-degree relative (mother, daughter, sister) who has had breast cancer, or you have multiple relatives affected by breast or ovarian cancer (especially before they turned age 50), you could be at higher risk of getting breast cancer.

Personal history of breast cancer.

If you have already been diagnosed with breast cancer, your risk of developing it again, either in the same breast or the other breast, is higher than if you never had the disease.

Race.

White women are slightly more likely to develop breast cancer than are African American women. Asian, Hispanic, and Native American women have a lower risk of developing and dying from breast cancer.

Radiation therapy to the chest.

Having radiation therapy to the chest area as a child or young adult as treatment for another cancer significantly increases breast cancer risk. The increase in risk seems to be highest if the radiation was given while the breasts were still developing (during the teen years).

Breast cellular changes.

Unusual changes in breast cells found during a breast biopsy (removal of suspicious tissue for examination under a microscope) can be a risk factor for developing breast cancer. These changes include overgrowth of cells (called hyperplasia) or abnormal (atypical) appearance.

Exposure to estrogen.

• starting menstruation (monthly periods) at a young age (before age 12)

• going through menopause (end of monthly cycles) at a late age (after 55)

• exposure to estrogens in the environment (such as hormones in meat or pesticides such as DDT, which produce estrogen-like substances when broken down by the body)

Pregnancy and breastfeeding.

Pregnancy and breastfeeding reduce the overall number of menstrual cycles in a woman’s lifetime, and this appears to reduce future breast cancer risk. Women who have never had a full-term pregnancy, or had their first full-term pregnancy after age 30, have an increased risk of breast cancer. For women who do have children, breastfeeding may slightly lower their breast cancer risk, especially if they continue breastfeeding for 1 1/2 to 2 years. For many women, however, breastfeeding for this long is neither possible nor practical.

DES exposure. Women who took a medication called diethylstilbestrol (DES), used to prevent miscarriage from the 1940s through the 1960s, have a slightly increased risk of breast cancer. Women whose mothers took DES during pregnancy may have a higher risk of breast cancer as well.

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