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    Home > Understanding Breast Cancer > Risk Factors and Prevention > Risk Factors Summary Table

      


    Risk Factors Summary Table

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    The table below lists the known risk factors for breast cancer and their related relative risks. A relative risk indicates how much higher the risk of breast cancer is in people who have a particular factor compared to people who don't. The larger a relative risk is, the higher the risk associated with the factor. A relative risk of 1.20, for example, means that 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 that someone with the factor has twice the risk (or 2-fold the risk) of someone without the factor.

    It's important to understand that the impact that a relative risk actually has largely depends on its underlying absolute risks. For example, the rate of breast cancer varies a great deal with age (see below), and this can greatly influence the number of extra breast cancer cases linked to a risk factor. When a condition is rare, as breast cancer is among very young women, a relative risk that sounds high will still mean that only a few extra cases will develop. By contrast, when a condition is more common, as breast cancer is among older women, even small relative risks can mean a lot more cases. Knowing the link between absolute and relative risks can help people put their health risks into proper perspective.

     

    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 1,837 (0.05%)

    30

     

    1 in 234 (0.4%)

    40

     

    1 in 70 (1.4%)

    50

     

    1 in 40 (2.5%)

    60

     

    1 in 28 (3.5%)

    70

     

    1 in 26 (3.9%)

         

    Lifetime risk

     

    1 in 8 (12.3%)

    (American Cancer Society, Breast Cancer Facts and Figures 2007-2008, [9])

     

    Note: Adding up relative risk numbers does NOT provide a total risk score (see Estimating Breast Cancer Risk).

     

    Factors that Increase the Risk of Breast Cancer

    Approximate Relative Risk

    Primary Reference(s)

    Being female

    Very high

    Ries et al., 2008 [5]

    Getting older

    Very high

    Ries et al., 2008 [5]

    Lobular carcinoma in situ (LCIS)

    7 - 10

    Morrow & Schnitt, 2000 [26]

    Confirmed inherited genetic mutations (BRCA1 or BRCA2)

    5 - 14

    Struewing et al., 1997 [10]
    Antoniou et al., 2003 [12]
    Risch et al., 2006 [54]

    Family history of breast cancer: Two immediate family members affected with breast cancer

    3 - 4

    Colditz et al., 1993 [135]
    Pharoah et al., 1997 [28]
    CGHFBC, 2001 [29]

    Family history of breast cancer: Mother affected before age 60

    2 - 3

    Colditz et al., 1993 [135]

    Family history of breast cancer: Mother affected after age 60

    1.4

    Colditz et al., 1993 [135]

    High breast density

    3 - 6

    Barlow et al., 2006 [136]

    Personal history of breast cancer (including DCIS)

    2 — 6

    Chen et al., 1999 [137]

    Benign breast conditions (proliferative): Atypical hyperplasia

    4

    Tamimi et al., 2005 [47]
    Hartmann et al., 2005 [48]
    Degnim et al., 2007 [138]

    Benign breast conditions (proliferative): Usual hyperplasia

    1.5 - 1.9

    Tamimi et al., 2005 [47]
    Hartmann et al., 2005 [48]

    Radiation exposure or frequent X-rays during youth

    2 — 4

    Hankcock et al., 1993 [36]
    Swerdlow et al., 2000 [37]
    Travis et al., 2003 [38]

    High levels of estrogen in the blood after menopause

    2

    EHBCCG, 2002 [139]

    High bone density

    1.5 - 3.5

    Zhang et al., 1997 [58]
    Zmuda et al., 2001 [59]

    Menopause at age 55 or older

    2

    Trichopoulos, 1972 [140]

    Not having children (compared to women who give birth at age 35 or younger)

    1.3

    Ewertz et al., 1990, [56]

    First child after age 35

    1.1-1.4

    Ewertz et al., 1990 [56]
    Rosner et al., 1994 [55]

    Overweight/weight gain

    1.2 - 1.5

    Van den Brandt et al., 2000 [65]
    Eliassen et al., 2006 [141]

    High socioeconomic status

    1.2 - 1.8

    Yost et al., 2001 [72]
    Braaten et al., 2005 [74]

    Lack of exercise

    1.2

    Rockhill et al., 1999 [85]
    McTiernan et al., 2003 [86]
    Tehard et al., 2006 [87]

    Drinking alcohol (2 - 4 drinks/day)

    1.4

    Smith-Warner et al., 1998 [142]
    EHBCCG, 2002 [82]

    Postmenopausal hormone use-estrogen plus progestin (current or recent use for 5 or more years)

    1.3 - 2.0

    WHI, 2002 [96]
    Beral et al., 2003 [97]
    Collins et al., 2005 [99]

    Current or recent use of birth control pills

    1.1 - 1.3

    CGHFBC, 1996 [124]

    First period before age 12

    1.2 - 1.3

    Kelsey et al., 1996 [122]
    Ma et al., 2006 [123]

    Being tall

    1.2

    Van den Brandt et al., 2000 [65]

    Not breastfeeding

    1.1 - 1.2

    CGHFBC, 2002 [133]
    Bernier et al., 2002 [132]

    Ashkenazi Jewish heritage

    1.1

    Egan et al., 1996 [78]

    Updated 09/14/09