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What are the risk factors for breast cancer?

There are some characteristics that are more common among groups of women who have developed breast cancer compared to groups of women who have not. These are called risk factors.

Generally it’s not possible to determine what causes breast cancer in an individual woman. It is important to remember that all women are at risk for breast cancer, no matter what their risk category. However, having certain risk factors increases a woman's chance of developing breast cancer.

Risk factors

  • Although breast cancer can occur at any age, increasing age is one of the strongest risk factors for breast cancer, with 75% of women diagnosed with breast cancer being over 50 and 95% of women diagnosed with breast cancer over 40.
  • Having an inherited genetic mutation, or a strong family history, (that is, having three or more first or second-degree relatives on the same side of the family with breast or ovarian cancer), is associated with an increased risk of breast cancer. For a small proportion of women, a strong family history can be an important factor indicating increased risk.
  • Genetic factors account for up to 5% of breast cancers overall, and up to about 10% of breast cancers in women under 40. Women concerned about their risk should discuss this with their doctor who can assess risk using iPrevent tool.
  • Being previously diagnosed with a non-invasive breast condition such as ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS), is associated with an increased risk of developing invasive breast cancer.
  • Women who start menstruation before the age of 12 or experience menopause later (at age 55 or after) have increased risk of breast cancer.

What can young women do to reduce their risk?

  • Keep your alcohol consumption down. Alcohol increases the risk of breast cancer and your risk increases with each standard drink per day. This includes beer, wine and spirits.
  • Women of all ages who engage in physical activity are at reduced risk of breast cancer compared to women who do not exercise. And the more physical activity you do, the bigger the benefits.
  • Having children at a younger age is associated with a decreased risk of breast cancer. The more children women have, the more their risk of breast cancer appears to be reduced.
  • Breastfeeding can reduce your breast cancer risk.

View the evidence about breast cancer risk factors.

Find out more

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