While an exact cause for breast cancer is still unknown, scientific research has revealed a number of controllable and uncontrollable factors that impact our risk of developing the disease.
Risk Factors for Breast Cancer You Cannot Control
Although we are unable to modify the risks associated with the uncontrollable factors, it is important to understand how they may impact an individual’s risk for breast cancer.
Risk Factors for Breast Cancer You Can Control
An estimated 30 percent of breast cancer cases are preventable through lifestyle changes (1). Most breast cancers are estrogen-related which is why many of the risk factors we can control involve keeping estrogen levels low. Although exposures that influence risk accumulate throughout a woman’s life, research suggests that early life exposures during breast development may be particularly critical.
Sex Assigned at Birth
The main risk for breast cancer is sex assigned at birth. Women are at the greatest risk of developing breast cancer, with 99% of breast cancer diagnoses occurring in women. And 1 in 8 women will be diagnosed with breast cancer in her lifetime. Men can also get breast cancer, but makeup about 1% of all breast cancer cases (10).
As a person ages, their risk of developing breast cancer increases. This is a result of longer overall exposure to estrogen. Although a person’s risk of developing breast cancer increases with age, young women can also be at risk for breast cancer.
Anyone can get breast cancer, but if you have a family history of breast cancer that increases your personal risk. That risk increases with the number of family members diagnosed with breast cancer. In addition, your risk increases if you have a first degree relative with a history of breast cancer such as a parent, sibling, or child, especially if they were diagnosed at an age younger than 50.
Previous Breast Cancer History
An individual with a history of breast cancer is not only at risk of recurrence, but they are also at a greater risk of developing a new breast cancer. Also, women with a history of ovarian cancer are at a greater risk of developing breast cancer.
Higher levels of breast density can increase your risk of breast cancer. Dense breast tissue can also make it harder for cancer to be detected on a traditional mammogram. If your mammogram reveals you have very dense breast breasts, you should speak to your doctor about additional screening that may be needed.
Abnormal or Mutated Genes
Genetic mutations can affect a person’s risk of developing breast cancer, particularly certain common gene mutations on the BRCA1 and BRCA2 genes. An individual with a mutation in the BRCA1 may have a 72% risk of developing breast cancer. And an individual with a BCRA2 mutation may have a 69% risk. It is important to know your family history and how it may affect your personal risk (11).
Age at First Menstruation/Late Menopause
Getting your first period very early (younger than 12) or late menopause (older than 55) increases risk because of the overall lifetime exposure to estrogen.
Healthy bodies need fat, but research suggests that eating a diet high in fat increases the risk of breast cancer. Keep your saturated fat intake to 20 grams or less per day and avoid trans-fat completely (2).
Fat cells in the body store high levels of estrogen, which increase the threat of breast cancer. Thus, maintaining a normal body weight is a crucial component in decreasing your risk.
30 minutes of moderate physical activity per day can help decrease your body fat percentage and the amount of estrogen in your body. It also strengthens your immune system, which enhances your body’s ability to recognize and eliminate early cancer cells (3).
Studies show that drinking alcohol—even just one drink per day—increases your risk for breast cancer. And it doesn’t matter what alcoholic drink you choose. They all impact your risk of developing breast cancer (4).
Smoking and vaping exposes the body to carcinogens and accelerates cancer tumor growth. Studies indicate that people who smoke during their teen years significantly increase their risk for breast cancer compared to people who don’t (5).
Late Pregnancy or No Pregnancy
Women who have children earlier in life have a reduced risk of breast cancer, compared to those who have children after age 35 or not at all (6).
Breastfeeding for a year or more reduces a woman’s overall risk of breast cancer. The longer a woman breastfeeds, the lower her risk drops. This seems to be most impactful on the risk of triple-negative breast cancer (7).
The use of oral contraceptives and hormonal intrauterine devices (IUD), have been shown to slightly increase the risk of breast cancer (8).
Combined Hormone Replacement Therapy
Use of combined HRT increases one’s risk of developing breast cancer and risk associated with HRT use never diminishes. It also increases the risk that breast cancer will be found at a more advanced stage and it may reduce the effectiveness of mammograms (9).
- Islami F, Goding Sauer A, Miller KD, et al. Proportion and number of cancer cases and deaths attributable to potentially modifiable risk factors in the United States. CA Cancer J Clin. 2018.
- “Healthy Fat Intake.” Cleveland Clinic, 2014, my.clevelandclinic.org/health/articles/11208-fat-what-you-need-to-know.
- Smith, Alma J et al. “The effects of aerobic exercise on estrogen metabolism in healthy premenopausal women.” Cancer epidemiology, biomarkers & prevention: a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology vol. 22,5 (2013).
- DeLuca, Gina. “Alcohol and Breast Cancer: What Is Their Current Relationship Status?” Maurer Foundation, 13 July 2020.
- Jones, M.E., Schoemaker, M.J., Wright, L.B. et al. Smoking and risk of breast cancer in the Generations Study cohort. Breast Cancer Res 19, 118 (2017).
- Chakravarthi, Balabhadrapatruni V S K, and Sooryanarayana Varambally. “Targeting the link between late pregnancy and breast cancer.” eLife vol. 2 e01926. 31 Dec. 2013.
- Anstey, Erica H, and Ginny Kincaid. “Breastfeeding for Cancer Prevention.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 1 Aug. 2019.
- March,L., Skovlund,C., Hannaford,P. et al., Contemporary Hormonal Contraception and the Risk of Breast Cancer.The New England Journal of Medicine. Dec 7, 2017.
- Ravdin,P., Cronin, K.,Howlader, N., et al. The Decrease in Breast-Cancer Incidence in 2003 in the United States. The New England Journal of Medicine.Apr 19, 2007.
- American Cancer Society. Breast Cancer Facts & Figures 2019-2020. Atlanta: American Cancer Society, Inc. 2019.
- Schwartz GF, Hughes KS, Lynch HT, et al. Proceedings of the International Consensus Conference on Breast Cancer Risk, Genetics, & Risk Management, April, 2007. Cancer. 2008.