There are many known and many suspected risk factors that can contribute to breast cancer. Breast cancer risks are sometimes unavoidable, but many can be controlled. Here are the more common and well-known risk factors that are proven through study.
Remember that not all risk factors are controllable. There are risks that cannot be avoided and some risks may not be definitive on their own, but are part of an overall likely lifestyle that could pose higher risks for breast and other cancers.
Some risks you're just born with.
Women are more likely to have breast cancer and the older a woman is, the more likely she will be diagnosed with breast cancer. Neither of these can be controlled. Neither can genetic risks, such as the known BRCA1 and BRCA2 gene mutations associated with some forms of breast cancer. Other factors such as race, breast density, and family histories of breast cancer are also factors.
There is little that can be done about these risks, but there are many risk factors that are choices rather than inherent.
Your lifestyle choices affect your breast cancer risk.
Being overweight or obese is one of the largest and most-associated risks for breast cancer (and many other illnesses and diseases) and goes hand-in-hand with the higher risk associated with those who have low amounts of daily physical activity. These are especially true after menopause.
Drinking alcohol and smoking tobacco are also closely associated with breast cancer risk. The more these substances are used (or abused), the higher the risk factor. Moderate alcohol use is not associated with higher risks, but smoking has been associated with cancer risks for decades.
When a woman chooses to have children is another important risk factor. Women who have children after the age of 30 are at higher risk for breast cancer while pregnancy on the whole is known to increase the risk of a certain type of breast cancer regardless of the woman's age (triple-negative cancer).
Breastfeeding is another risk factor in breast cancer, with studies showing that women who breast fed their children are less likely to develop many types of breast cancer.
Hormone therapy and birth control are associated with breast cancer risks. The use of hormone therapies during and after menopause, especially combined hormone replacements, increase the risk of getting breast cancer. Birth control, meanwhile, is only marginally, but still known to affect breast cancer risk. Oral contraceptives, the most commonly-used type of birth control, have a slight increase in breast cancer risk associated with them.
Other factors that need more assessment to be sure might also increase risks.
Risk of breast cancer could increase or decrease with certain vitamin intake, chemicals in the environment and exposures to them, and exposure to second-hand smoke. Although these and some other factors are not directly associated with increased breast cancer risk, they are suspected of being so and are being further studied.