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Risk Factors for Breast Cancer

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The most significant risk factor for breast cancer is being a woman. 

All women are at risk of breast cancer and the older you are, the higher the risk. While men can develop breast cancer, the vast majority of cases occur in women.

The usual statistic is that one in eight women will develop breast cancer over her life. If you live to age 90, the risk goes up to one in seven (about 14%), according to the American Cancer Society.

As you can see, you have no control over the two most significant risk factors: your sex and your age. It is important to note that even with the one in seven risk factor, there is an 86% chance you will not develop breast cancer.

The incidence of breast cancer by age bracket is more instructive than these general numbers and you can find those statistics further down in this article.

While these statistics look at the whole population of women, they are not necessarily accurate for individuals.

This is where other risk factors come into the picture. Researchers know that if a woman has some of the other risk factors, she has a higher risk of developing breast cancer than a similar group of women without the other risk factors.

According to the Centers for Disease Control and Prevention, several factors may affect your risk of developing breast cancer. These include:

  • Getting olde​​​r
  • Not having children, or having your first child later in life
  • Starting your first menstrual period at an early age
  • Beginning menopause at a late age
  • Having a personal history of breast cancer or certain benign breast diseases, such as atypical ductal hyperplasia
  • Having close family relatives (such as a mother, sister, father, or daughter) who have had breast cancer
  • Having a genetic condition, such as certain mutations in your BRCA1 or BRCA2 genes
  • Having been treated with radiation therapy to the breast or chest
  • Being overweight, particularly after menopause
  • Using hormone replacement therapy for a long time
  • Using oral contraceptives
  • Drinking alcoho​​l
  • Being physically inactive

Scientists are studying how best to prevent breast cancer. Ways to help you lower your risk of getting breast cancer include the following:

  • Stay physically active by getting regular exercise
  • Maintain a healthy weight
  • Avoid using hormone replacement therapy (HRT), or find out the risks and benefits of HRT and if it is right for you
  • Limit the amount of alcohol that you drink

Risk Factors by the Numbers

Put another way, risk factors beyond your age and your sex change your chances of developing breast cancer. How those changes are expressed depends on whether they are relative or absolute risks.

Relative risk describes how your risk changes with the addition of a risk factor and compares that to persons who did not add a risk factor. If your risk is 10% and doing X increases your risk 25%, then your risk is 25% higher than a woman who did not add the risk factor.

Absolute risk calculates what that change really means. For example, if your risk was 10% and it increased 25%, your absolute risk would be 12.5%. (10% x 25% = 2.5%. 10% + 2.5% = 12.5%).

Understanding these numbers can help you and your doctor make more informed treatment decisions. If you just knew the relative risk (or benefit) increased 25% in a particular situation, you might make one decision. However, if you knew the absolute risk (or benefit) was only 12.5%, you might choose differently.

According to breastcancer.org,​ the absolute risk of developing breast cancer during a particular decade of life is lower than 1 in 8. The younger you are, the lower the risk. For example:

  • From age 30 to 39, absolute risk is 1 in 233, or 0.43%. This means that 1 in 233 women in this age group can expect to develop breast cancer. Put another way, your odds of developing breast cancer if you are in this age range are 1 in 233.
  • From age 40 to 49, absolute risk is 1 in 69, or 1.4%
  • From age 50 to 59, absolute risk is 1 in 38, or 2.6%
  • From age 60 to 69, absolute risk is 1 in 27, or 3.7%

As you can see, the older a woman is the higher the risk of developing breast cancer. However, these numbers apply to the whole population. Your chances of developing breast cancer may be higher or lower depending on other risk factors.

​Discuss the risks and benefits of potential treatments with your doctor to fully understand the choices you make.​

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