5 Breast Cancer Risk Factors You Might Not Know About

Even with a healthy lifestyle, you may have risks factors of which you were unaware. Here are five breast cancer risk factors you might not know about.

Breast cancer has some commonly known risks. Some are within your control, like smoking, and some are just about who you are like the biggest risk: being a woman.

Regardless, you can lower your breast cancer risk by eating healthy, exercising and limiting alcohol. Plus, with regular screenings, you can diagnose breast cancer in its early stages, when it’s easier to fight.

Even with a healthy lifestyle, you may have risks factors of which you were unaware. Here are five breast cancer risk factors you might not know about:

Pregnancy and breast-feeding

Several aspects of pregnancy, including breast-feeding, are related to a lower risk of breast cancer, according to the National Cancer Institute:

  • Early age at first full-term pregnancy — For example, a woman who gives birth before age 20 has about half the risk of a woman who gives birth after 30.
  • Increasing number of births — The risk declines with each child.
  • Preeclampsia — Women who have had preeclampsia may have a decreased risk.
  • Breast-feeding duration — Breast-feeding for at least a year is associated with a decreased risk.

Lowering your breast cancer risk is important, but your decisions about children and breast-feeding will encompass many other considerations.

“The decision to have a child is very personal, complicated and requires commitment and support,” breastcancer.org says. “ If having children earlier rather than later is an option for you, you may want to do that. Still, this is a highly individual decision affected by many factors besides breast cancer risk.”


White women are more likely to develop breast cancer than women of other races, according to the Centers for Disease Control and Prevention. However, black women are more likely to die from breast cancer.

One expert points out that biology, physical activity and sedentary behavior play a role, and she is conducting research to understand the disparity in breast cancer death rates by studying the relationships between activity level and biological makeup and comparing those connections in white and black women.

First period and last period

The younger a girl is when she has her first period — called menarche — the higher risk she has for breast cancer later in life, according to research in the Lancet Oncology medical journal. There is also a slightly higher risk of breast cancer in women who have menopause later than other women.

“Since the effect on breast cancer risk of one year younger at menarche is significantly greater than that of one year older at menopause, these findings suggest that the effects of each may not be acting merely by lengthening the total duration of women's reproductive years,” the researchers write.

Hormone replacement therapy

After menopause, this therapy helps women’s bodies minimize hot flashes and mood swings. However, a study of 1 million women found that HRT increases breast cancer risk, particularly in women who use combined HRT, taking oestrogen and progestogen, instead of just oestrogen, according to Cancer Research UK.

“But it’s important to remember that the increased cancer risk with HRT is small compared to many other risk factors, like smoking or being overweight HRT is only responsible for a very small proportion of cancer cases,” the organization says on its website.


If you had radiation to your chest or face before age 30, for example, to treat Hodgkin disease or acne, you have a higher risk of developing breast cancer later in life, according to breastcancer.org. The risk is highest if you had the radiation during adolescence when your breasts were developing.

Emerging risks

Researchers are discovering previously unknown issues that increase breast cancer risk, according to breastcancer.org:

  • Low levels of vitamin D
  • Light exposure at night — women who work at night or live in areas with high external light have a higher risk of breast cancer
  • Diethylstilbestrol exposure — pregnant women and their children who were exposed to DES from the 1940s to the 1960s to prevent miscarriage have a slightly higher risk of breast cancer
  • Exposure to chemicals in cosmetics, food, lawns and gardens, plastic, sunscreen, water and grilled meat

Recognizing these risk factors doesn’t necessarily mean changing how you live or the decisions you make, but it can help you be more aware and vigilant in monitoring your breast health.

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