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© Copyright 2013
Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine


Risk factors

Most scientists agree that these things affect the risk of breast cancer. Some may apply to you, but others may not.

Age
Sex
Family history
Jewish ethnicity
Height
Weight
Physical activity
Alcohol
Vitamins
Birth weight
Age at first period
Age at first birth
Number of births
Breast feeding
Birth control pills (oral contraception)
Age at menopause
Post menopausal hormones
Tamoxifen and Raloxifene
Benign breast disease
Ionizing radiation



Age and breast cancer
The risk of developing breast cancer increases with age. Rates are generally low in women younger than 40, but they start to increase after age 40 and are highest in those 70 and older. The average age breast cancer is found is 61.

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Sex and breast cancer
Over 99 percent of all cases in the United States are diagnosed in women. Breast cancer can develop in men, but it is rare.

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Family history and breast cancer
Women who have a mother or sister with breast cancer have a higher risk of the disease, especially if the relative’s cancer was diagnosed at a young age. The risk goes up if a woman has multiple relatives with the disease. This is because some breast cancers are linked to mutations (changes) in the genetic structure (DNA) of the body's cells that can be passed from generation to generation.

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Jewish ethnicity and breast cancer
Jewish women have a higher risk of breast cancer, especially women of Ashkenazi descent. This is because they are more likely to have genetic mutations linked to breast cancer risk. Genetic mutations are inherited changes in the genetic structure (DNA) of the body's cells that can be passed from generation to generation.

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Height and breast cancer
Tall women have a higher risk of breast cancer. Researchers don’t know exactly why, but it may be related to the fact that tall people grow more. Some of the same hormones and other factors that make people grow may also increase the chance that dividing cells become abnormal and turn cancerous.

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Weight and breast cancer
Women who maintain a healthy weight have a lower risk of breast cancer, especially if they are post-menopausal. One reason is that fat tissue affects different hormone levels in the body.  Too much fat tissue can lead to higher hormone levels and increase the risk of cancer.

People who maintain a healthy weight also have a lower risk of colon cancer, kidney cancer, pancreatic cancer, heart disease, diabetes and stroke. And women have a lower risk of uterine cancer.


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Physical activity and breast cancer
People who are physically active for at least 30 minutes a day have a lower risk of breast cancer, possibly because physical activity affects hormone levels and other growth factors in the body. Being physically active is also one of the best ways to help maintain a healthy weight. In addition, physically active people also have a lower risk of colon cancer, heart disease, diabetes and stroke.

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Alcohol and breast cancer
Women who have less than one drink a day have a lower risk of breast cancer. (One drink is a can of beer, a glass of wine, or a shot of hard liquor.) Alcohol may raise the level of some hormones in the body. High levels of certain hormones after menopause may cause cells in the breast to become cancerous.

Drinking alcohol also increases the risk of other diseases like colon cancer, and high blood pressure. However, drinking moderate amounts (less than 1 drink/day for women and less than 2 drinks/day for men) can help decrease the risk of heart disease and diabetes.


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Vitamins and breast cancer
In general, there are no strong links between specific vitamins and the risk of breast cancer.  However, in women who drink moderate amounts of alcohol, the vitamin folate (found in most multivitamins and B-complex vitamins) seems to protect against the increased risk associated with drinking alcohol.

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Birth weight and breast cancer
Women who weighed more at birth have a higher risk of breast cancer before menopause. Researchers aren’t sure exactly why this is, but they are studying different influences like pregnancy hormones and other prenatal factors to learn more about breast cancer development.

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Age at first period and breast cancer
Women who get their first period at an early age have a higher risk of breast cancer. This is because an early period exposes a woman's body to greater amounts of estrogen (a female reproductive hormone) over her lifetime. More estrogen over a long period of time can increase the risk that cells in the breast become cancerous.

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Age at first birth and breast cancer
Women who first give birth to a child at a late age have a higher risk of breast cancer. One reason may be that pregnancy permanently changes breast tissue, making it less likely to become cancerous. The later this change occurs in a woman’s life, the more time the breast cells have to become abnormal and become cancerous.

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Number of births and breast cancer
Women who have fewer than 2 children have a higher risk of breast cancer. One reason is that pregnancy changes hormone levels and breast tissue in a way that helps protect breast cells from becoming cancerous. The fewer pregnancies a woman has, the less her breast tissue changes and the less protection she gets.

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Breast feeding and breast cancer
Women who breast feed for a total of one year or more have a lower risk of breast cancer. This is because breast feeding can cause changes in hormones and in breast tissue that help protect the cells from becoming cancerous.

Women who breast feed also have a lower risk of ovarian cancer.


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Birth control pills and breast cancer
Women have a higher risk of breast cancer while they are taking birth control pills. Birth control pills can have positive and negative effects on a woman's health. If taken for at least 5 years, birth control pills can lower a woman's risk of colon cancer, uterine cancer and ovarian cancer. But while she's taking them, they raise her risk of breast cancer, heart attack and stroke. For some women, they can also cause side effects like nausea and vomiting.

Taking birth control pills and smoking can be a deadly combination. Together, they greatly increase the risk of a heart attack and stroke. All women who smoke should quit for good as soon as possible.

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Age at menopause and breast cancer
Women who go through menopause (when regular menstrual periods stop) at a later age have a higher risk of breast cancer. This is because a late menopause exposes a woman's body to greater amounts of the hormone estrogen over her lifetime. These higher levels of estrogen increase the risk that breast cells will become cancerous.

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Post-menopausal hormones and breast cancer

Post-menopausal hormones are medications that help ease the symptoms of menopause, like hot flashes and vaginal dryness. The most commonly prescribed post-menopausal hormones are estrogen and progesterone, which the body stops making in large quantities after menopause.

Women who take post-menopausal hormones for 5 or more years have a higher risk of breast cancer. This is because post-menopausal hormones raise the level of estrogen in a woman's body, and high levels of estrogen after menopause may cause cells in the breast to become cancerous.

Post-menopausal hormones can have both positive and negative effects on a woman's health. These hormones may cause abnormal growth of cells, increasing the risk of breast cancer, but different hormones affect risk differently. The combination of estrogen plus progesterone seems to increase breast cancer risk more that estrogen alone, but estrogen alone increases the risk of uterine cancer. In contrast, post-menopausal hormones may lower a woman’s risk of colon cancer and osteoporosis (bone loss). Post-menopausal hormones were once thought to lower the risk of heart attack, but it is now unclear exactly how they affect the risk of heart disease.


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Tamoxifen, Raloxifene and breast cancer
Tamoxifen and Raloxifene are medications prescribed for women at high risk of breast cancer. They block the effects of the hormone estrogen in breast tissue and can help reduce the risk of breast cancer. However, these medications also have serious side effects. They are not right for everyone and can only be prescribed by a doctor.

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Benign breast disease and breast cancer
Benign breast disease is a large group of non-cancerous breast conditions. Different types of benign breast disease include cysts (fluid filled sacs), fibroadenomas (solid lumps of tissue), and hyperplasia (abnormal increase in the size and number of cells).

Most types of benign breast disease never become cancer, but there is a condition called atypical hyperplasia that is related to breast cancer. Atypical hyperplasia is a condition where the increased number and size of breast cells look very abnormal. Women with atypical hyperplasia have an increased risk of developing breast cancer.


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Ionizing radiation and breast cancer
Women who have been exposed to high-dose radiation (such as radiation received in treatment of Hodgkin’s disease, repeated fluoroscopic studies for tuberculosis, and proximity to atomic bomb blasts) are at higher risk of breast cancer, especially if the exposure occurred at a young age. However, these high-dose exposures are very rare. It is important to recognize that regular x-rays and mammograms use only low-dose exposures and do not significantly increase the risk of cancer.

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