Breast cancer, like many other illnesses, is a disease associated with a number of risk factors. Some, such as age and family history, are unavoidable, but others, such as lack of exercise and obesity, can be influenced by changes in behavior. It's important to keep risk factors in perspective — having one or more doesn't necessarily guarantee that you will develop the disease. Still, although the following isn't a complete list, it's a good idea to get a sense of what your personal breast cancer risks are, and more important, make a plan for steps you can take to minimize them.
Breast Cancer Risks You Can't Control
The older you are, the greater your risk. Approximately one out of eight cases of invasive breast cancer are found in women younger than age 45, while about two out of three cases are found in women 55 or older, according to the American Cancer Society.
White women have a slightly higher risk of developing breast cancer than do African-American, Hispanic, Asian, or Native American women.
Menstruation and pregnancy
Research suggests that the more menstrual cycles you have, the greater your risk of breast cancer, possibly due to the greater lifetime exposure to estrogen and progesterone. That means that women who began menstruating at an early age (12 or younger) and/or experienced menopause after age 55 have been shown to have a slightly higher breast cancer risk.
Having a first-degree relative (a mother, sister, or daughter) with breast cancer approximately doubles a woman's risk and having two first-degree relatives with breast cancer increases a woman's risk fivefold. That said, it's important to note that women with a family history of breast cancer make up only 5 to 10 percent of all women with the disease, so don't assume you're not at risk if breast cancer isn't in your family. A family history of ovarian cancer may also increase the risk of breast cancer.
Having had breast cancer in one breast makes a woman three to four times as likely to develop cancer in the opposite breast.
Women who inherit a gene mutation from a parent (the most common mutations are of the BRCA1 and BRCA2 genes) face an increased risk of breast cancer. There are a number of other genetic mutations that can also increase a woman's risk of breast cancer, although at a lower level than the risk brought on by BRCA1 or BRCA2.
Dense breast tissue
Women with dense breasts — meaning the breasts have more firm than fatty tissue — have a higher risk of breast cancer.
Exposure to radiation therapy or DES
Undergoing radiation in the chest area (as in treatment for cancers like lymphoma) or having taken the now-banned drug diethylstilbestrol (DES) — which was prescribed for some pregnant women until about 1970 — can increase a woman's risk of developing breast cancer.
Breast Cancer Risks You Can Control
Another reason to maintain a healthy weight: Putting on pounds, especially after menopause, has been associated with an increase in breast cancer risk. A 2006 Harvard Medical School study also found that weight loss after menopause was linked to a decrease in breast cancer risk.
Lack of exercise
Several studies have suggested a link between physical activity and a reduction in breast cancer risk. One study from the Women's Health Initiative, a large observational study of over 74,000 women, showed that as little as 1.25 to 2.5 hours of brisk walking every week reduced the risk of breast cancer by 18 percent.
Pregnancy and breastfeeding
Because exposure to hormones is decreased during pregnancy, women who have never been pregnant have a higher risk of breast cancer, and women who have been pregnant — especially before age 30 — are at lower risk. Also, breastfeeding provides some protection against the development of breast cancer.
Long-term use of postmenopausal hormone therapy has been shown to increase the risk of breast cancer. The use of combined estrogen and progestin (which doctors prescribe to women who haven't undergone a hysterectomy) has been linked to a higher risk of breast cancer, but there is currently insufficient evidence to point to a link between estrogen-only therapy (which doctors prescribe to women who have undergone a hysterectomy) and breast cancer.
The more you drink, the higher your risk of breast cancer, according to several large-scale studies. One study led by doctors at the Kaiser Permanente Medical Care Program in Oakland, California, showed that one or two drinks a day increased a woman's risk of developing breast cancer by 10 percent and having more than three drinks a day raised the risk by 30 percent — regardless of whether wine, beer, or hard liquor was consumed. Experts aren't certain exactly how alcohol raises breast cancer risk but believe it has something to do with the fact that alcohol raises the amount of hormones in the blood to levels that could potentially cause cancer.
Remember, for all breast cancer risks, knowledge is your best weapon. Talk to your doctor about preventive measures if you have one or more risk factors you can't control, and take steps toward a healthier lifestyle to minimize those you can.