Top 10 Risk Factors for Breast Cancer

by PJ Hamel Patient Expert

Think you’re at risk for breast cancer? Everyone’s at some risk; but certain factors increase that risk. Here are the top factors affecting breast cancer risk.

1. Age and sex

The #1 risk factor for being diagnosed with breast cancer is being a woman, followed closely by growing older. Breast cancer risk increases as you age; women between the ages of 65-80 are at highest risk for breast cancer. At age 20, your risk is just 1 in 1,681. At age 70, it’s increased to 1 in 27.

2. Personal history

If you’ve ever been diagnosed with breast cancer, your risk of being diagnosed a second time is increased; the degree of increase depends on the type and severity of your previous breast cancer.

In addition, being diagnosed with a “pre-cancer” (e.g., DCIS, atypical hyperplasia) increases your risk of later being diagnosed with breast cancer.

3. Genetics

About 5 to 10 percent of all breast cancers are due to genetic mutations, including the familiar BRCA1 and BRCA2 mutations. While less than 1 percent of the general population carries these mutations, Jewish women of eastern European descent are more likely to have them.

4. Dense breasts

Breast tissue varies in density, woman to woman. Some women’s breasts have a high percentage of fibrous and connective tissue compared to fat; this condition is known as “dense breasts.”

Studies have shown that women with dense breasts are significantly more likely to be diagnosed with breast cancer than those whose breasts have a higher ratio of fat to other tissues.

5. High estrogen levels

Women with higher levels of estrogen are more likely to develop breast cancer. Some common factors that increase estrogen include:

•Postmenopausal obesity;

•Bearing children after age 30 (or not at all);

•Use of oral contraceptives;

•Use of HRT (hormone replacement therapy).

6. Family history

Having two or more first-degree relatives (parent, sibling, or child) who’ve been diagnosed with breast cancer increases your risk, especially if any were diagnosed before age 50. One first-degree relative with breast cancer also increases your risk, though less significantly.

7. High postmenopausal bone density

Strong bones are healthy bones – but they can also indicate an increased risk for breast cancer.

What’s the connection? Estrogen increases bone strength; the higher a woman’s level of estrogen post-menopause, the stronger her bones will be – and, unfortunately, the greater her risk of breast cancer.

8. High-dose radiation to the chest

If you had high-dose radiation therapy to your chest area before the age of 30, usually as a result of Hodgkin’s disease, this increases your risk of developing breast cancer. Thankfully, this represents only a small percentage of the population."¨"¨

9. Diet

A high-fat diet and alcohol consumption have both been linked to an increased risk of breast cancer. Try to eat a lower-fat diet, including healthy fats (e.g., nuts, olive oil); and limit yourself to one drink a day – 1 ½ ounces (1 ½ shots) liquor, 5 ounces wine, or 12 ounces beer.

10. Disrupting sleep rhythms

There’s a growing body of evidence that long-term disruption of your body’s circadian rhythm, by working an overnight shift; or by traveling across multiple time zones (e.g., flight attendants) increases breast cancer incidence. Researchers theorize this is due to decreased melatonin exposure; melatonin affects estrogen levels, and is a tumor suppressor.

More helpful articles:

Determining Your Breast Cancer Risk: a HealthCentral Explainer

Risks and Benefits: Understanding the Statistics That Affect You

Breast Cancer and Women Under 40: What’s Your Risk Right Now?

Breast Cancer and Women Over 40: What’s Your Risk Right Now?

Is Breast Cancer Hereditary? A HealthCentral Explainer

How to Lower Your Risk of Breast Cancer


DeSantis, Carol. "Breast Cancer Facts & Figures 2011-2012." 2012. Accessed January 13, 2016.

Breast cancer survivor and award-winning author PJ Hamel, a long-time contributor to the HealthCentral community, counsels women with breast cancer through the volunteer program at her local hospital. She founded and manages a large and active online survivor support network.

PJ Hamel
Meet Our Writer
PJ Hamel

PJ Hamel is senior digital content editor and food writer at King Arthur Flour, and a James Beard award-winning author. A 16-year breast cancer survivor, her passion is helping women through this devastating disease. She manages a large and active online survivor support network based at her local hospital and shares her wisdom and experience with the greater community via