Anything that increases the chance of developing a disease is called a risk factor. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer.

There are different kinds of risk factors. Some factors, like a person's age or race, can't be changed. Others are linked to cancer-causing factors in the environment. Still others are related to personal choices such as smoking, drinking, and diet. Some factors influence risk more than others, and your risk for breast cancer can change over time, due to factors such as aging or lifestyle.

Risk factors for breast cancer include the following:

			age
			age at the start of menstruation
			age at first live birth
			age at menopause
			number of first-degree relatives (mother, sisters, daughters) with breast cancer
			number of previous breast biopsies (whether positive or negative)
			at least one breast biopsy with atypical hyperplasia
			dense breast tissue on a mammogram
			use of birth control pills or hormone replacement therapy
			a high-fat diet
			drinking alcohol
			low physical activity
			obesity
			environmental exposures

But having a risk factor, or even several, does not mean that you will get the disease. Most women who have one or more breast cancer risk factors never develop the disease, while many women with breast cancer have no apparent risk factors (other than being a woman and growing older). Even when a woman with breast cancer has a risk factor, there is no way to prove that it actually caused her cancer.

As women get older, the risk does increase. Assuming a woman lives to age 90, her risk of getting breast cancer over her lifetime is about 14%. What this means is that an average of about one out of every seven women will get breast cancer over a 90-year life span. You can also look at it in a more positive way - there is an 86% chance that you WON'T get breast cancer.