No matter your genes or lifestyle, no one has a 100% chance of being diagnosed with breast cancer. But no one is completely protected either. With 1 in 5 men and women globally being diagnosed at some point in their life, it’s safe to assume that you or someone you know will have a brush with breast cancer. For developing a cancer screening plan that’s unique to you, it’s important to understand all the risk factors that can affect you, including ones you can change and the ones you can’t.
1. Being A Woman
While men do get breast cancer, it is rare. 99% of all breast cancer cases are found in women. For this reason, some women with an extremely high risk of breast cancer choose to proactively have a prophylactic mastectomy.
2. High Breast Density
Having dense breasts not only makes mammograms harder to read (meaning a breast cancer diagnosis could be caught later or missed altogether), but dense breasts also double the likelihood of developing breast cancer. To combat this, some states, including New York state, have a breast density law that requires mammography clinics to inform patients if they have dense breasts. Women with dense breast can also choose to make breast ultrasounds part of their regular screening regimen.
Breast cancer risks rise as we age. Women aged 40 and under account for only 7% of all breast cancer cases. Women are most likely to be diagnosed in their 50s and 60s.
4. Having a Family History of Breast Cancer
15% of women who are diagnosed with breast cancer have a family history of breast cancer. Women who have a first-degree relative, such as a mother, a daughter, or a sister, with breast cancer double their risk. Women with more than one first-degree relative triple their risk.
5. Having BRCA or Other Breast Cancer Gene Mutations
Currently, nine genes, when mutated, have been shown to increase breast cancer risk levels, most notably BRCA1 and BRCA2. Women that are BRCA-positive have a 70% chance of developing breast cancer in their lifetime.
6. Having A Personal Breast Cancer History
If you have been previously diagnosed with breast cancer, you are more likely to be diagnosed again than someone who’s never been diagnosed.
7. Ethnicity or Race
Breast cancer is most commonly diagnosed in white women, but Black women have the highest mortality rate.
Depending on the data, taller women have an increased risk of breast cancer by 8-38% per 10cm. It is not clear if height itself causes the increased risk, or if height is indirectly related to some other risk factor.
9. Having Another Breast Condition
Women with atypical ductal hyperplasia (ADH) or atypical lobular hyperplasia (ALH) have a 400-500% chance of being diagnosed with breast cancer. Having lobular carcinoma in situ can raise a women’s risk by 7-12 times.
10. Early Menstruation
Menstruation age is a little-talked-about risk factor for breast cancer. One meta-analysis that looked at data from 100 different studies showed that for every year earlier a woman started her period, her breast cancer risk level raised 5%.
11. Late Menopause
Scientists theorize that late menopause works to raise breast cancer risk in much the same way as early menstruation—by exposing a woman’s body to more female hormones during her lifetime. For every year earlier that a woman is able to attain menopause, she reduces her risk of being diagnosed with breast cancer by 3%.
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12. Being Exposed To Diethylstilbestrol (DES)
Diethylstilbestrol is a synthetic form of estrogen. It is no longer commonly used, but was prescribed heavily from about 1940-1971 to pregnant women. Daughters of these women who were exposed in utero have an up to 40 times increase of breast cancer after the age of 40.
13. Having Chest Radiation Treatment
Being treated with high levels of chest radiation at a young age, for instance for Hodgkin or non-Hodgkin lymphoma, significantly increases your chance of being diagnosed with breast cancer. Don’t worry about the low-level radiations of mammograms though!
14. Not Having Children
Breast cancer risk raises slightly for women who skip having children, have children after the age of 30, or have less children. Similar to early menstruation and late menopause, researchers believe this phenomenon is linked to women being exposed to less breast-cancer-related hormones during their lifetimes.
15. Combined Hormone Therapy Treatment
Using combined hormone therapy in post-menopausal women increases breast cancer diagnosis rates. In addition, it makes it more likely the cancer will be found at a later and less-treatable stage.
16. Hormonal Birth Control
Hormone-based oral contraceptives slightly increase breast cancer risk. Although there are few studies done on other hormone-based birth control such as rings, patches, or shots, it is believed the higher risk also extends to these methods since they are hormone-based.
17. Not Breastfeeding
Some studies show that women who breastfeed, especially for longer than a year, have a slightly less chance of being diagnosed with breast cancer.
Smoking is most commonly associated with lung cancer, but it also increases your chance of developing breast cancer. In fact, women who smoked at any point in their lives have a 14% higher risk of a breast cancer diagnosis and women who started before the age of 17 have a 24% higher risk.
19. Not Exercising
Regular exercisers have a lower risk of breast cancer. For those that are diagnosed, physical activity is linked to longer survival and a lower rate of cancer recurrence. If you can’t quite hit your exercise goals, don’t despair. Studies have shown that while it’s best to hit a certain amount of weekly exercise, women who fall short still benefit.
20. Being Overweight After Menopause
While obesity offers an oddly protective effect for younger women, obese women who have reached menopause have a 20-40% increased risk of breast cancer diagnosis compared to women with normal weights.
21. Drinking Alcohol
Alcohol in any amount raises breast cancer risks. Women who have an average of 1 drink a day have a 7-10% higher chance of being diagnosed over a non-drinker and women who have 2-3 drinks have a 20% higher chance.
The Bottom Line
The truth is, we don’t know every reason why people are diagnosed with breast cancer. And we don’t always understand the risk factors we do know about. We do, however, after decades of study, have some very good scientific evidence about things that could generally increase or decrease our risk levels. The important thing is to be aware of how at risk we personally are and develop a screening plan with our doctor based on this. While some things we cannot control, like being born a woman, there are many things we can control. Every woman should do a regular mammogram and monthly breast self-exam to detect breast cancer as early as possible. And beyond breast cancer, almost every aspect of our lives could benefit from a healthier lifestyle of less alcohol, less tobacco, less calories (if you are overweight), and more exercise.
- “Breast Cancer in Men,” CDC
- “Breast Cancer Facts & Figures 2017-2018,” American Cancer Society
- “Height and Breast Cancer Risk: Evidence From Prospective Studies and Mendelian Randomization,” Journal of the National Cancer Institute, 2015
- “Breast Cancer Risk Factors You Cannot Change,” American Cancer Society
- “Lifestyle-related Breast Cancer Risk Factors,” American Cancer Society
- “Reproductive factors and risk of hormone receptor positive and negative breast cancer: a cohort study,” BMC Cancer, 2013
- “A comparative study of pre- and post-menopausal breast cancer: Risk factors, presentation, characteristics and management,” Journal of Pharmacy Practice and Research, 2014
- “Diethylstilbestrol (DES) and Cancer,” National Cancer Institute
- “Reproductive History and Cancer Risk,” National Cancer Institute
- “Study Links Smoking to Increased Risk of Breast Cancer,” American Journal of Managed Care, 2017
- “For Women with Breast Cancer, Regular Exercise May Improve Survival,” National Cancer Institute, 2020