Breast Cancer Risk Factors
The main risk factors for breast cancer include sex, age and family history/genetics. Lifestyle factors such as hormone-replacement therapy, moderate-heavy alcohol use and obesity also contribute to risk.
Lifestyle/Modifiable Risk Factors
Obesity and being overweight: Higher body fat after menopause increases risk.
Physical inactivity: Exercise reduces risk; inactivity raises it.
Alcohol consumption: Even moderate drinking increases breast cancer risk.
Reproductive factors: Early menstruation (before 12), late menopause (after 55), later age at first childbirth, not breastfeeding, and nulliparity all increase risk by prolonging hormone exposure.
Diet and environmental exposures: Diet quality, vitamin D levels, and exposure to certain chemicals or radiation may influence risk. Diets high in fruits, vegetables, and soy may lower risk, while high-fat or processed foods may increase risk.
Non-Modifiable Risk Factors
Female sex: Women are much more likely to develop breast cancer than men due to hormonal differences and breast tissue sensitivity to oestrogen and progesterone.
Age: Risk increases with age, with most cases diagnosed after age 50. For example, risk at age 40 is about 1.5%, rising to over 4% by age 70.
Family history and genetic factors: Having first-degree relatives with breast cancer increases risk, especially if relatives were diagnosed young. Inherited mutations in high-risk genes like BRCA1 and BRCA2 significantly raise risk (up to 45–85% lifetime risk) as well as mutations in TP53, PALB2, CHEK2, and others.
Race/ethnicity: Incidence and outcomes vary; white non-Hispanic women have higher incidence, while black women have higher mortality rates.
Other Possible Risk Factors
Breast density: Women with dense breasts on mammograms are at higher risk.
Previous breast abnormalities: Certain benign breast conditions or previous breast cancer increase risk.
Medical conditions: Conditions like atrial fibrillation treated with cardiac glycosides have been linked with increased risk.