The table below lists the known risk factors for breast cancer and their relative risks.
What is relative risk?
A relative risk shows how much higher the risk of breast cancer is in people with a certain risk factor compared to people without the factor. The larger a relative risk is, the higher the risk linked to the factor. For example, a relative risk of 1.20 means someone with the factor has a 20 percent (or 1.2-fold) higher risk of breast cancer than someone without the factor. A relative risk of 2.0 means someone with the factor has twice the risk (or 2-fold the risk) of someone without the factor.
Relative risk and absolute risk
The impact of a relative risk depends on the underlying absolute risk of the disease. For example, the rate of breast cancer increases with age (see below), and this impacts the number of extra breast cancer cases linked to a risk factor. When a disease is rare, as breast cancer is among very young women, even a high relative risk means that only a few extra cases will occur. By contrast, when a disease is more common, as breast cancer is among older women, even a small relative risk can result in many more cases.
Absolute risk of breast cancer in American women by age
|
If current age is:
|
Absolute risk of developing breast cancer in the next 10 years is:
|
20
|
1 in 1,760 (0.06%)
|
30
|
1 in 229 (0.4%)
|
40
|
1 in 69 (1.4%)
|
50
|
1 in 42 (2.4%)
|
60
|
1 in 29 (3.4%)
|
70
|
1 in 27 (3.7%)
|
| |
Lifetime risk
|
1 in 8 (12.2%)
|
Source: American Cancer Society, Breast Cancer Facts & Figures 2011-2012 and Cancer Facts & Figures 2011 [4,6].
|
Factors that Increase the Risk of Breast Cancer
|
Approximate Relative Risk
|
| Age (getting older) |
Very high |
| Being female |
Very high |
| BRCA1 and BRCA2 inherited genetic mutations |
5-30 |
| Family history of breast cancer: Two immediate family members diagnosed with breast cancer |
3-4 |
| Family history of breast cancer: Mother diagnosed before age 60 |
2-3 |
| Family history of breast cancer: Mother diagnosed after age 60 |
1.5-2 |
| High breast density |
4-5 |
| Hyperplasia (proliferative benign breast condition): Atypical hyperplasia |
4 |
| Hyperplasia (proliferative benign breast condition): Usual hyperplasia |
1.5-1.9 |
| Lobular carcinoma in situ (LCIS) |
7-12 |
| Personal history of cancer: Invasive breast cancer or ductal carcinoma in situ (DCIS) |
1.5-10 |
| Personal history of cancer: Hodgkin's disease |
15-25 |
| Radiation exposure or frequent X-rays during youth: For breast cancer diagnosed at age 40 |
11 |
| Radiation exposure or frequent X-rays during youth: For breast cancer diagnosed at age 60 |
3.6 |
| Childbearing: Not having children (compared to women who give birth at age 35 or younger) |
1.3 |
| Childbearing: First child after age 35 (compared to women who give birth at age 35 or younger) |
1.1-1.4 |
| High androgen levels in the blood |
2.2 |
| High estrogen levels in the blood (after menopause) |
2 |
| Age at first period (before age 12) |
1.2-1.3 |
| Age at menopause (age 55 or older) |
1.3 |
| Alcohol: 2-4 drinks/day |
1.2-1.4 |
| Ashkenazi Jewish heritage |
1.1 |
| Height (being tall) |
1.2 |
| Birth control pill use: Current or recent use |
1.1-1.3 |
| High socioeconomic status |
1.2-1.8 |
| Postmenopausal hormone use: Estrogen plus progestin (current or recent use for 5 or more years) |
1.3-2.0 |
| Overweight/weight gain |
1.3-1.6 |
| Not breastfeeding |
1.1-1.2 |
| High bone density |
1.5-2.7 |
| Lack of exercise |
1.1-1.2 |
| Light at night/shift work |
1.5 |
| Adapted from selected sources [41,48-49,54-55,63,72,74-76,86,89-90,92,102,104-105.120-125,129-131,139,141,146,148,158-160,175-178,191-192,196-199]. |
Table note: Adding relative risks does not give a total risk score.
Learn about estimating breast cancer risk.
Updated 11/02/11
