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Breast Cancer Risk Factors Table

The table below provides the relative risk of breast cancer linked to a variety of factors. The relative risk represents how much higher or lower the risk of breast cancer is for a person who has the particular factor compared to a person who does not.

Factors are grouped based on the strength of the scientific evidence underlying each risk.

  • Established and probable factors have the strongest evidence behind them, and are recognized as linked (or not linked in some instances) to breast cancer.
  • Possible factors have less evidence behind them; they suggest links to breast cancer but need more study before solid conclusions can be made.
  • Insufficient or inconsistent factors are backed by few studies or the studies to date have very mixed results, which don't allow comment on any potential link with breast cancer.

Click on any of the factors to learn more.

Relative Risk Categories
Strong increase Moderate increase Weak increase No increase or decrease Weak decrease Moderate decrease Strong decrease

Established Factors

Recognized as linked (or not linked in some instances) to breast cancer. 		 
Approximate risk of breast cancer
BRCA1 or BRCA2 gene mutation Strong increase in risk
Carcinoma in situ Strong increase in risk
Family history of breast cancer
Strong increase in risk
Moderate increase in risk
High breast density Strong increase in risk
Hyperplasia (benign breast disease)
  • Atypical
 Strong increase in risk
  • Usual
 Moderate increase in risk
Personal history of cancer Strong increase in risk
Childbearing
  • Not having children
 Moderate increase in risk
  • Having a first child after age 35
 Moderate increase in risk
High bone density Moderate increase in risk
Radiation exposure or frequent X-rays during youth Moderate increase in risk
Age at first period < 12 years Weak increase in risk
Age at menopause > 55 years Weak increase in risk
Alcohol consumption
  • 1-2 drinks / day
 Weak increase in risk
  • 2-4 drinks / day
 Weak increase in risk
Ashkenazi Jewish heritage Weak increase in risk
Birth control pills (current/recent use only) Weak increase in risk
Being tall Weak increase in risk
High socioeconomic status Weak increase in risk
Mammography (radiation exposure) Weak increase in risk
Postmenopausal hormone use
  • Estrogen only
 Weak increase in risk
  • Estrogen + progestin
 Moderate increase in risk
Breastfeeding Weak decrease in risk
Abortion No increase or decrease in risk
Hair dyes No increase or decrease in risk
 

Probable Factors

Recognized as linked (or not linked in some instances) to breast cancer, although not as definitively as established factors. 		 
 
Approximate risk of breast cancer
High levels of blood estrogen Moderate increase in risk
Weight gain
  • Premenopausal
 No increase or decrease in risk
  • Postmenopausal
 Moderate increase in risk
African-American ethnicity
  • Premenopausal
 Weak increase in risk
  • Postmenopausal
 No increase or decrease in risk
Body weight
  • Premenopausal
 Moderate increase in risk
  • Postmenopausal
 Weak increase in risk
Physical activity
  • Premenopausal
 No increase or decrease in risk
  • Postmenopausal
 Weak decrease in risk
Blood organochlorine levels (exposure to certain types of pesticides and industrial chemicals) No increase or decrease in risk
Breast implants No increase or decrease in risk
Electromagnetic fields (from utility wires, electric blankets, microwave ovens, fluorescent lighting, etc.) No increase or decrease in risk
 

Possible Factors

Recognized as potentially linked (or not linked in some instances) to breast cancer, but need more study before solid conclusions can be made 		 
 
Approximate risk of breast cancer
IGF-1 hormone levels
  • Premenopausal
 Moderate increase in risk
  • Postmenopausal
 No increase or decrease in risk
Light at night Weak increase in risk
Red meat consumption
  • Premenopausal
 Weak increase in risk
  • Postmenopausal
 No increase or decrease in risk
Dietary fat consumption Weak decrease in risk
Carotenoid intake Moderate decrease in risk
Dairy consumption
  • Premenopausal
 No increase or decrease in risk
  • Postmenopausal
 No increase or decrease in risk
Deodorant use No increase or decrease in risk
Aspirin use No increase or decrease in risk
Fertility drug use No increase or decrease in risk
Fruit and vegetable consumption No increase or decrease in risk
Glycemic load/carbohydrate intake No increase or decrease in risk
 

Factors with inconsistent results or insufficient evidence

For these factors, there are very few studies to date and/or results are highly inconsistent. More research is needed to comment on any potential relationship.

Antibiotic use
Body care cosmetics containing parabens
Bras or under-wire bras
Breast size
Caffeine
Cell phones
French fry consumption
Hair Relaxers		 Left-handedness
Plastics
Secondhand smoke exposure
Smoking
Soy intake
Stress
Trauma to the breast