Common myths about breast cancer abound, relayed through word of mouth and the Internet, frightening women unnecessarily.

Despite the rumors, you can't get breast cancer from electric blankets, deodorant, microwave-oven use, or under-wire bras, says the American Cancer Society (ACS). The National Cancer Institute (NCI) has found no association between induced and spontaneous abortions and breast cancer, dispelling another popular myth.

That's not to say your lifestyle doesn't matter. The ACS says that your health habits may play a role in helping to reduce your risk for this serious disease, and they're particularly important as you get older.

An American woman has a 1-in-8 lifetime risk of developing the disease, but overall lifetime risk increases dramatically after age 40. According to the ACS, about two out of three women with invasive breast cancer are age 55 or older when they are diagnosed.

Screening mammogram

A mammogram won't reduce your risk for breast cancer, but it can help detect the disease in its early, most treatable, stages. The risk for breast cancer increases with age, especially after age 40, the American Cancer Society (ACS) says. As a general guideline, the ACS recommends a yearly mammogram after age 40. Your health care provider, however, may propose another strategy based on your situation.

In general, your risk for breast cancer nearly doubles if one or more close relatives on either your mother's or your father's side developed the disease before menopause or have had ovarian cancer at any age. But other factors, such as being diagnosed with certain types of benign breast disease -- the extra growth of apparently normal cells -- also can increase your risk.

Risk factors for breast cancer:

• Genetics. Five to 10 percent of cases of breast cancer are hereditary, as a result of changes in genes (mutations). Women who inherit a BRCA1 or BRCA2 mutation have around an 80 percent chance of developing breast cancer during their lifetime. When they do develop cancer, it is often at a younger age than in women who are not born with one of these gene mutations.

• Family history of breast cancer. According to the ACS, 20 to 30 percent of women with breast cancer have a family member with the disease. If you have a relative (mother, sister, grandmother, or aunt) who had breast cancer before age 50, your risk is increased. Your risk is also higher if you have two or more relatives with breast or ovarian cancer.

• Previous breast cancer. A woman who has cancer in one breast is at higher risk for developing a new cancer in the other breast or in another part of the same breast, the ACS says.

• Race. White women are slightly more likely to develop breast cancer than other groups, the ACS says. African American women are more likely to die of breast cancer.

• Breast biopsy results. A biopsy result of atypical hyperplasia increases a woman's breast cancer risk by four to five times; a result of proliferative breast disease without atypical hyperplasia increases the risk by 1.5 to 2 times. A biopsy result of fibrocystic changes without proliferative breast disease does not increase breast cancer risk.

• Radiation treatment. A woman who had radiation treatment in the chest area as a child or younger woman is at higher risk, the ACS says.

• Menstruation history. Women who started their periods when they were younger than 12 or who went through menopause after age 55 are at slightly higher risk for breast cancer. This same risk applies to women who have not had children or had their first child after age 30, according to the ACS. This may be because risk could be related to the total number of menstrual periods a woman has during her lifetime.

• Hormone therapy. Long-term use of estrogen and progesterone, called combined hormone therapy (HT), for longer than five years puts a woman at slightly higher risk for breast cancer, the ACS says. Estrogen alone (ET) does not appear to increase the risk for breast cancer. Other health risks are associated with HT and ET. You should discuss the issue carefully with your health care provider to find out what is best for you.

• Obesity. The relationship between obesity and breast cancer is complex. According to the ACS, risk appears to increase for women who gained weight after menopause, not for those who have been overweight since childhood. Fat tissue may contribute to increased risk because it can increase estrogen levels.

• Alcohol. The risk for breast cancer increases with the amount of alcohol consumed. When compared with women who are nondrinkers, women who have one alcoholic drink a day have a very small increase in risk, and those who have two to five drinks daily have about 1-1/2 times increased risk.

Be sure to tell all your health care providers that you have an increased risk.

Drug therapy

A woman with a family history of breast cancer or with a genetic mutation of a BRCA gene may be able to reduce her chances of breast cancer. The first step is genetic testing to find out if she has a mutation in either the BRCA1 or BRCA2 gene.

The drug tamoxifen, which blocks the effects of estrogen on breast tissue, has been used for years to treat some breast cancers. It is now used to reduce the incidence of breast cancer in high-risk women. It is important to be aware that tamoxifen can have serious side effects, such as blood clots, the ACS says.

Another anti-estrogen drug, raloxifene, reduces the risk of invasive breast cancer to the same degree as tamoxifen, although it does not protect as effectively against non-invasive cancer.

Cancers caused by the BRCA1 gene mutation may not be prevented by tamoxifen or raloxifene.

Other types of drugs being studied for breast cancer prevention in postmenopausal women are aromatase inhibitors (AI). In premenopausal women, estrogen is produced by the ovaries and other tissues of the body using a substance called aromatase. In postmenopausal women, estrogen is produced only by tissues in the body. AIs do not block estrogen production by the ovaries, but they can block other tissues from making this hormone. That's why they are used mostly in women who have reached menopause, when the ovaries are no longer producing estrogen. AIs have side effects such as causing joint pain and stiffness, and bone loss, leading to a higher risk for osteoporosis. Currently, three AIs are approved by the U.S. Food and Drug Administration: anastrazole (Arimidex), exemestane (Aromasin) and letrozole (Femara).

Clinical breast exams

A breast examination by a physician or nurse trained to evaluate breast problems should be part of a woman's physical examination. The ACS recommends:

Between the ages of 20 and 39, women should have a clinical breast examination by a health professional every three years.

It's especially important for postmenopausal women to avoid being overweight, the ACS says, because that increases the risk for breast cancer.

Plus, maintaining a healthy weight throughout your life also can reduce your risk for many other conditions, including diabetes and heart disease.

Limit alcohol

If you drink, do so in moderation. Studies suggest that women who have more than two alcoholic drinks a day have about 1-1/2 times the risk of getting breast cancer compared with women who drink no alcohol, the ACS says. One drink equals 12 ounces of beer, 4 to 5 ounces of wine, or 1-1/2 ounces of hard liquor.

Get moving

Among its many benefits, physical activity has been shown to reduce breast cancer risk, the ACS says. No one knows exactly why, but it may be because of the effects of activity on hormones, energy balance, weight reduction, and the immune system.

Researchers aren't sure how much exercise to recommend, or the type of activity. Until researchers know more, aim for at least 45 to 60 minutes of intensional physical activity, such as walking, jogging, or strength training, at least five days a week, the ACS says.