Many factors are linked to breast cancer risk. There are factors that increase breast cancer risk and a few that lower risk. Some factors affect risk a great deal and others by only a small amount.
Although we have learned a lot, we still do not understand what causes breast cancer to develop at a certain time in a certain person. It's likely a combination of risk factors (some of which are still unknown). But why a certain combination of factors might cause breast cancer in one person, but not in another, is still unclear.
In this section, you’ll get a better understanding of factors that may affect your breast cancer risk.
The data in this section come from two main types of research studies:
The goal of these studies is to give information that helps support or disprove an idea about a possible link between an exposure (like alcohol use) and an outcome (like breast cancer) in people. Although they have the same goal, observational studies and randomized controlled trials differ in the way they are conducted and in the strength of the conclusions they reach.
Learn more about different types of research studies.
Animal studies add to our understanding of how and why some factors cause cancer in people. However, there are many differences between animals and people that make it hard to translate findings directly from one to the other.
Animal studies are also designed differently than human studies. They often look at exposures in larger doses and for shorter durations than are suitable for people. Thus, animal studies can lay the groundwork for research in people, but in order to draw conclusions for people, we need human studies.
All data presented within this section of this website come from human studies unless otherwise noted.
Some organizations conduct research and/or prepare summary reports of research on certain exposures shown to have a link (or no link) to breast and other types of cancer. These agencies are a good place to find detailed, up-to-date information (for example, if you have concerns over a news item on cancer).
IARC is a part of the World Health Organization. The CDC, NTP and FDA are all part of the U.S. Department of Health and Human Services.
Facts for Life: Breast Cancer Risk Factors
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