What are the breast cancer risk factors?

Having risk factors doesn't mean you will get breast cancer

Up to 70 percent of the women diagnosed with breast cancer have no known risk factors, while some women with many risk factors never get the disease. Having risk factors does not mean you are guaranteed to get breast cancer -- only that you are at a higher risk. Despite the discrepancy between risk factors and actually getting the disease, the National Cancer Institute recommends avoiding those risk factors you can control and increasing preventative factors for breast cancer.

Risk factors for breast cancer

Risk factors for breast cancer fall into two categories: Those you cannot change and those you can control.

Risk factors for breast cancer that you cannot control

Gender: The American Cancer Society says women are 100 times more likely to get breast cancer than men, due to the women's breast cells having more exposure to the reproductive hormones estrogen and progesterone.

Age: As you get older, your risk for breast cancer increases. According to the Dr Susan Love Research Foundation, about 80 percent of breast cancer cases occur in women over 50 years old. That does not mean younger women are immune, however.

Family history of breast cancer: Women with a first-degree relative (daughter, sister or mother) with breast cancer have double the risk of developing breast cancer.

Personal history of breast cancer: Women who have had breast cancer are at a higher risk of developing breast cancer again.

Genetics: The chance of a woman getting breast cancer is significantly higher if she has inherited alterations in the breast cancer genes BRCA1 and BRCA2.

Atypical hyperplasia: This is a precancerous condition in which too many cells line the wall of a milk duct or lobule in the breast and no longer look like normal cells. Women with this condition have four to six times the risk of developing breast cancer than the general population, according to the Mayo Clinic.

Dense breast tissue: This puts you at an increased risk of breast cancer and may also make it more difficult to detect breast cancer with mammograms.

Menstrual periods: The higher the number of menstrual periods a woman has in her lifetime, the higher her risk of getting breast cancer. Women who start menstruating at an early age and start menopause later are at a higher risk.

Risk factors for breast cancer that you can change

Hormone replacement therapy: Post-menopausal hormone therapy or hormone-replacement therapy has been associated with an increased risk of breast cancer.

Oral contraception: Research indicates that women who use birth control pills are at an increased risk for breast cancer, but that the risk declines once oral contraceptive use stops.

Not breastfeeding: Women who breastfeed are at a lower risk of developing breast cancer, most likely due to having fewer total menstrual periods in their lifetimes.

Having kids later or not at all: Women who have children after age 30 or have had no children have a slightly higher breast cancer risk. This may be due to the fact that pregnancy reduces a woman's total number of lifetime menstrual cycles.

Obesity: Being overweight or obese increases a woman's risk of developing breast cancer, especially after menopause.

Alcohol consumption: According to the American Cancer Society, the use of alcohol is clearly linked to an increased risk of breast cancer, with the risk increasing with the number of drinks consumed.

Lack of physical activity: A growing body of evidence indicates that exercise can reduce a woman's risk of developing breast cancer (among other health conditions).

Diet: High-calorie diets put a woman at risk for becoming obese, increasing her risk of breast cancer.

Secondhand smoke: Research suggests an increased risk of breast cancer for women exposed to secondhand smoke.

Environmental factors: This is an area of growing research that currently has no conclusive causal links. Some environmental toxins have been linked to breast cancer in animals, however. Therefore, experts recommend keeping up to date on the research and, to be safe, limiting your exposure to any suspect substances.

More about reducing your breast cancer risk

• What causes breast cancer?
• Breast cancer: Measuring your risk
• Quick guide to breast cancer screening
• Breast lumps: Symptoms, treatment and prevention
• Breast cancer guide for teens
• The Anticancer Diet